US20250084512A1

US20250084512A1 - Galvanically-active in situ formed particles for controlled rate dissolving magnesium alloy

Info

Publication number: US20250084512A1
Application number: US18/945,479
Authority: US
Inventors: Timothy Ryan DUNNE; Lei Zhao; Jiaxiang Ren; Peng Cheng; Yu Liu
Original assignee: China National Petroleum Corp; Beijing Huamei Inc CNPC
Current assignee: China National Petroleum Corp; Beijing Huamei Inc CNPC; CNPC USA Corp
Priority date: 2022-06-03
Filing date: 2024-11-12
Publication date: 2025-03-13

Abstract

A dissolvable magnesium alloy can be used for components of a downhole tool. The dissolvable magnesium alloy can be dissolved completely and controlled at a dissolving rate so as to be compatible with downhole operations, including hydraulic fracturing operations. The alloy includes nickel at 0.04-0.4% by weight and the balance of magnesium. The alloy is dissolvable in KCl at 2.1% by weight and 95° C. with a dissolving rate in a range of 10-100 mg/cm2/hr, yield strength in a range of 18-37 ksi, ultimate tensile strength in a range of 29-47 ksi, and elongation in a range of 8-40%.

Description

CROSS REFERENCE RELATED APPLICATION

This application is a continuation-in-part patent application of International application Ser. No. 17/805,368, filed on Jun. 3, 2022, the content of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a material composition in the oil and gas industry. More particularly, the present invention relates to dissolvable metal alloys to form components of downhole tools. Even more particularly, the present invention relates to a dissolvable magnesium alloy for components in hydraulic fracturing operations.

BACKGROUND

Downhole tools are commonly used in oil and gas production. A borehole is drilled through a hydrocarbon bearing formation, and downhole tools, such as plugs and sleeves are positioned along and within the borehole. The plugs close and open portions of the borehole so that zones may be selectively isolated. A plug can include at least one dissolvable metallic component. As an assembly, the plug must hold a pressure differential around 7.5 ksi. A sleeve opens and closes to make the fluid connection between the borehole and the formation. The downhole tools work to isolate and connect the zone for various operations to prepare and produce the hydrocarbons from the formation. When the operations are complete in the zone, components of the downhole tool or even the entire downhole tool may require removal. For example, a dissolvable frac ball set in a plug to trigger a seal may be removed by injecting a solvent targeted to the dissolvable frac ball so that the seal is removed. After the fracturing operation, the components dissolve in the wellbore fluid, typically a potassium chloride brine. Alternatively, the entire plug may be removed.
Dissolvable alloys were developed for the manufacture of downhole tool components in the oil and gas industry. There are mainly two types of metallic dissolvable alloys: magnesium and aluminum based alloys. These alloys may be cast and mechanically worked in a variety of manners, including but not limited to vertical direct chill casting, vacuum induction melting, and extrusion.
The disclosure of dissolvable metal alloys, and particularly, dissolvable magnesium alloys are known in the prior art intended for a variety of conditions. US Publication No. 20160168965 published on 16 Jun. 2016 for Marya, U.S. Pat. No. 8,425,651, issued on 23 Apr. 2013 to Xu et al, US Publication No. 20140286810 published on 25 Sep. 2014 for Marya, US Publication No. 20180238133 published on 23 Aug. 2018 for Fripp et al, US Publication No. 20190032173 published on 31 Jan. 2019 for Sherman et al, US Publication No. 20190055810 published on 21 Feb. 2019 for Fripp et al, US Publication No. 20190271061 published on 5 Sep. 2019 for Tang et al, U.S. Pat. No. 10,081,853 issued on 25 Sep. 2018 to Wilks et al, U.S. Pat. No. 9,757,796 issued on 12 Sep. 2017 to Sherman et al, and US Publication No. 20160256091 published on 20 Aug. 2019 to Cho et al, disclose dissolvable magnesium alloys.
It is an object of the present invention to provide a dissolvable magnesium alloy.
It is another object of the present invention to provide a dissolvable magnesium alloy for components of a downhole tool.
These and other objectives and advantages of the present invention will become apparent from a reading of the attached specification.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention include a dissolvable alloy for components of a downhole tool. The assembly of a downhole tool with a dissolvable metallic component, which comprises a dissolvable alloy, having from about 0.04 to about 0.4 wt % nickel and the balance of magnesium, holds a pressure differential around 7.5 ksi and dissolves in a wellbore fluid after downhole operation. The alloy is dissolvable in KCl at 2.1% by weight and 95° C. with a dissolving rate in a range of 10-100 mg/cm²/hr, yield strength in a range of 20-40 ksi, ultimate tensile strength in a range of 25-45 ksi, and elongation in a range of 7-40%.
Optionally in any embodiment, the alloy may comprise about 0-20% lithium by weight, about 0-15% gadolinium by weight, about 0-15% yttrium by weight, about 0-2% copper by weight, about 0-2% zirconium by weight, about 0-15% aluminum by weight.
Optionally in any embodiment, the alloy may comprise up to about 10 wt % total of other elements, which comprises one of manganese, neodymium, cerium, calcium, iron, bismuth, indium, or silver.
Optionally in any embodiment, said copper is about 1.4 wt %, said gadolinium is about 3.1 wt %, said nickel is about 0.15 wt %, and said yttrium is about 4.0 wt %.
Optionally in any embodiment, said copper is about 1.47 wt %, said aluminum is about 10.1 wt %, said zinc is about 0.45 wt %, said nickel is about 0.15 wt %, and said manganese is about 0.16 wt %.
Optionally in any embodiment, said copper is about 0.4 wt %, said nickel is about 0.04 wt %, and said aluminum is about 0.5 wt %.
Optionally in any embodiment, said gadolinium is about 3.1 wt %, said copper is about 0.4 wt %, said nickel is about 0.04 wt %, and said aluminum is about 0.5 wt %.
Optionally in any embodiment, said copper is about 0.4 wt %, said nickel is about 1.4 wt %, and said aluminum is about 5.6 wt %.
Optionally in any embodiment, said gadolinium is about 1.56 wt %, said zirconium is about 0.4 wt %, said nickel is about 0.04 wt %, and wherein said zinc is about 3.88 wt %.
Optionally in any embodiment, said lithium is about 11 wt %, said gadolinium is about 1.0 wt %, said yttrium is about 0.6 wt %, said nickel is about 0.4 wt %, said copper is about 0.2 wt %, and wherein said zinc is about 3.3 wt %.
In another embodiment, an alloy may comprise about 0-20% lithium by weight, about 0-15% gadolinium by weight, about 0-15% yttrium by weight, about 0-2% copper by weight, about 0-2% zirconium by weight, about 0-15% aluminum by weight, about 0.04% to about 0.4% nickel by weight; the balance of magnesium (Mg) and inevitable impurities, so as to be dissolvable in KCl at about 2.1% by weight and about 93° C. with a dissolving rate in a range of from about 10 to about 100 mg/cm²/hr, yield strength in a range of from about 25 to about 37 ksi, ultimate tensile strength in a range of from about 35 to about 45 ksi, and elongation in a range of from about 10 to about 19%.
Optionally in any embodiment, the copper to nickel ratio is within the range of about 50:1 to about 0.1:1 wt %.
Optionally in any embodiment, said range of aluminum is about 7 to about 12 wt %, particularly when the range of aluminum to copper is in the range of about 3.5:1 to about 60:1 wt %.
Optionally in any embodiment, said range of zinc is about 0.5 to about 3 wt %, particularly when the range of copper to zinc is in the range of about 0.07:1 to about 4:1 wt %.
In further embodiment, an alloy may comprise about 0.04% to about 0.4% nickel by weight; about 0.2% to about 2% copper by weight; and the balance of magnesium (Mg) and inevitable impurities, wherein the alloy yields strength in a range of from about 25 to about 37 ksi, ultimate tensile strength in a range of from about 35 to about 45 ksi, and elongation in a range of from about 10 to about 19%.
Optionally in any embodiment, the alloy yields strength in a range of from about 25 to about 37 ksi, ultimate tensile strength in a range of from about 35 to about 45 ksi, and elongation in a range of from about 10 to about 19%.
Optionally in any embodiment, the alloy may further comprise about 0-20% lithium by weight, about 0-15% gadolinium by weight, about 0-15% yttrium by weight, about 0-2% zirconium by weight, about 0-15% aluminum by weight.
Optionally in any embodiment, the alloy may further comprise up to about 10 wt % total of other elements, which comprises one of manganese, neodymium, cerium, calcium, iron, bismuth, indium, or silver.
In further embodiment, a dissolvable magnesium composite that at least partially forms a ball, a frac ball, a tube, a plug or other tool component that is to be used in a well drilling or completion operation, said dissolvable magnesium composite includes in situ precipitate, said dissolvable magnesium composite comprising a mixture of magnesium or a magnesium alloy and an additive material, said magnesium composite includes greater than about 50 wt. % magnesium, said in situ precipitate includes said additive material, said additive material includes one or more metal materials selected from the group consisting of: a) nickel, wherein said nickel constitutes about 0.04-0.4 wt. % of said dissolvable magnesium composite, and b) copper, wherein said copper constitute about 0.1-10 wt. % of said dissolvable magnesium composite, said dissolvable magnesium composite has a dissolution rate of at least 10 mg/cm²/hr in 2.1 wt. % KCl water mixture at 93° C.
Optionally in any embodiment, said dissolvable magnesium composite has yield strength in a range of from about 25 to about 37 ksi.
Optionally in any embodiment, said dissolvable magnesium composite has ultimate tensile strength in a range of from about 35 to about 45 ksi.
Optionally in any embodiment, said dissolvable magnesium composite has an elongation in a range of from about 10 to about 19%.
Optionally in any embodiment, said magnesium alloy comprises greater than 50 wt. % magnesium and no more than 10 wt. % aluminum, and one or more metals selected from the group consisting of 0.5-10 wt. % aluminum, 0.1-2 wt. % zinc, and 0.15-2 wt. % manganese.
Optionally in any embodiment, magnesium alloy comprises greater than 50 wt. % magnesium and no more than 10 wt. % aluminum, and one or more metals selected from the group consisting of 0.5-10 wt. % gadolinium, 0.1-6 wt. % yttrium, and 0.15-12 wt. % lithium.
Optionally in any embodiment, said additive material includes nickel. Said nickel constitutes 0.15-0.4 wt. % of said dissolvable magnesium composite.
In further another embodiment, a dissolvable magnesium cast composite comprising a mixture of magnesium or a magnesium alloy and an additive material, said additive material includes one or more metals selected from the group consisting of a) copper wherein said copper constitutes at least 0.01 wt. % of said dissolvable magnesium cast composite, and b) nickel wherein said nickel constitutes at least 0.01 wt. % of said dissolvable magnesium cast composite, said magnesium composite includes in situ precipitate, said in situ precipitate includes said additive material, a plurality of particles of said in situ precipitate having a size of no more than 50 μm, said magnesium composite has a dissolution rate of at least 5 mg/cm²/hr. in 3 wt. % KCl water mixture at 90° C.
In yet another embodiment, a dissolvable magnesium cast composite comprising a mixture of magnesium or a magnesium alloy and an additive material, said additive material includes a) nickel wherein said nickel constitutes 0.01-0.4 wt. % of said dissolvable magnesium cast composite, said dissolvable magnesium cast composite includes in situ precipitate, said in situ precipitate includes said additive material, said dissolvable magnesium cast composite has a dissolution rate of at least 75 mg/cm²/hr. in 3 wt. % KCl water mixture at 90° C.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph illustrating a comparison of stress and elongation for an embodiment of the alloy of the present invention with additional additives according to one embodiment. All values are as-extruded with no heat treatments.

FIG. 2 is a graph illustrating the yield strength, ultimate tensile strength, and ductility at room temperature for alloys 1 through alloy 6.

FIG. 3 is a plot of the mechanical properties of alloy 6 as a function of temperature. The mechanical properties are stable as a function of temperature.

FIG. 4 is a plot of the yield strengths normalized to room temperature for alloy 1 through alloy 6 as a function of temperature. The plot shows a prevalent decrease in properties with increasing temperature. Rare earth elements such as gadolinium stabilize mechanical properties with increasing temperature. The plot teaches for the two embodiments with gadolinium (alloys 4 and 5), there is a loss greater than 15%. The addition of yttrium maintains the maximum property loss to 10%.

FIG. 5 is a graph illustrating an ultra-high ductility magnesium, Alloy 7. The addition of lithium to the material greatly increased the ductility at the expense of mechanical strength.

FIG. 6 is a graph illustration contrasting the ductility of alloy 7 with other embodiments in the disclosure.

FIG. 7 demonstrates the unique performance of alloy 7 over two other high elongation embodiments, alloy 6 (left) and alloy 5 (center). These show the standard failure patterns of magnesium in compression due to the HCP crystal structure. The lithium addition overcomes the limitations of the magnesium HCP crystal structure.

FIG. 8 is a graph illustration as-cast dissolution rate of six embodiments of the alloy of the present invention at 95 C in a range of salinities. The dissolution rate range shows the chemistries cover applications where either quick or slow dissolution is needed.

FIGS. 9 a through 9 g present a magnified view of a microstructure of an embodiment of the alloy of the present inventions with different additives at a range of magnifications. The figures teach the resultant phases and microstructures that generate the measured properties.

FIG. 9 a shows that alloy 1 is at 1500× magnification via SEM on left and EDS at 3500× on right identifies several phases that accelerate corrosion.

FIG. 9 b shows that alloy 2 is at 350× magnification via SEM on left and EDS at 3500× identifies Mg₁₇Al₁₂in large quantities creating semi-enclosed cells that will reduce the rate of corrosion and increase the mechanical strength.

FIG. 9 c shows alloy 3 is at 350× magnification via SEM on left. EDS at 3500× identifies Mg₁₇Al₁₂in moderate quantities creating poorly-enclosed cells that will minimally delay corrosion while enhancing mechanical properties.

FIG. 9 d shows that alloy 4 is at 500× magnification via SEM on left, EDS at 5000× on right.

FIG. 9 e shows that alloy 5 is at 350× magnification via SEM on left, EDS at 3500× identifies the locations of the LPSO phases at 1, 2, and 3.

FIG. 9 f shows that alloy 6 is at 350× magnification via SEM on left and EDS at 1500× on the right.

FIG. 9 g shows that Alloy 7 is at 350× magnification via SEM on left. And EDS at 1500× on the right.

FIG. 10 teaches the change in microstructure from the addition and/or subtraction of gadolinium from the alloy.

FIG. 11 teaches the impact yttrium has on microstructure.

FIG. 12 a through 12 d show phase diagrams that are used to select the fractions of alloying elements to be added to an alloy.

FIG. 12 a shows binary phase diagram of magnesium and aluminum.

FIG. 12 b shows binary phase diagram of magnesium and zinc.

FIG. 12 c shows binary phase diagram of magnesium and nickel.

FIG. 12 d discloses binary phase diagram of magnesium and copper.

FIG. 13 is an X-Ray Diffraction measurement of phases for alloy 3 showing the creation of beneficial phases in an embodiment of the alloy of the present invention.

FIG. 14 is an X-Ray Diffraction measurement of phases for alloy 6 showing the creation of beneficial phases in an embodiment of the alloy of the present invention.

FIG. 15 is a graph illustrating a CALPHAD simulation of the embodiment of the alloy of the present invention in FIG. 5 , showing the mole fraction of phases formed during casting.

FIG. 16 is a graph illustrating comparison of alloy 4 to an alloy using the same weight percentage rare earth, but substituting neodymium for gadolinium.

DETAILED DESCRIPTION OF THE INVENTION

Before the description of the embodiment, terminology, methodology, systems, and materials are described; it is to be understood that this disclosure is not limited to the particular terminologies, methodologies, systems, and materials described, as these may vary. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions of embodiments only, and is not intended to limit the scope of embodiments. For example, as used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. In addition, the word “comprising” as used herein is intended to mean “including but not limited to.” Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.
Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as size, weight, reaction conditions and so forth used in the specification and claims are to the understood as being modified in all instances by the term “about”.
Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
As used herein, the term “about” means plus or minus 10% of the numerical value of the number with which it is being used. Therefore, about 50% means in the range of 45%-55%.
Magnesium alloy is an alloy based on magnesium and some other additional elements. It has the following characteristics: low density (about 1.8 g/cm³), high specific strength, high specific elastic modulus, good heat dissipation, good shock absorption, better impact load resistance than aluminum alloy, and good resistance to organic and alkali corrosion. Magnesium alloy has a wide range of applications in various industrial fields, mainly used in aviation, aerospace, transportation, chemical, rocket, oil and gas industries and other industrial sectors. Magnesium is the lightest metal in the practical applications. The specific gravity of magnesium is about ⅔ that of aluminum and ¼ that of iron. Magnesium alloy has high strength and high rigidity. On the other hand, magnesium alloy is chemically active among existing materials and can be used in industrial fields where structural materials are required to be degradable.
Although the chemical properties of magnesium alloys are relatively active, the reaction rate of magnesium with a medium such as water, aqueous solutions and water-oil mixtures is extremely slow at normal temperature. The main reason is that the magnesium hydroxide formed by the reaction can prevent further reaction between magnesium and the medium. Even if the magnesium alloys are heated to the boiling temperature of water, only a very slow reaction can be observed. Because the reaction rate of conventional magnesium alloy with medium is low within a certain temperature range and the controllable range is narrow, it cannot meet the demands of industrial applications. Thus, for the manufacture of structural and functional integrated components in industries such as oil and gas sector, there is a great need for an improved alloying process that would enhance the rate of chemical reaction between magnesium alloy and the medium, while maintaining the high strength of the magnesium alloy.
The present invention presents a magnesium alloy which would destroy the continuity of magnesium hydroxide formed during the reaction between magnesium and a medium, thereby accelerating the reaction between magnesium and the medium. The medium could be aqueous solutions such as fresh water, pond water, lake water, salt water, brine water, produced water or flow back water and their mixture with crude oil etc. In one embodiment, the chemical reaction can be: Mg+2H₂O→Mg(OH)₂+H₂(gas)
By adjusting the proportion of each element in the magnesium alloy, the reaction rate of the magnesium alloy with the medium can be regulated, resulting in a relatively wider controllable range, and the magnesium alloy material is flexible, so that the magnesium alloy meets the application requirements of the industrial sector such as oil and gas industry.
The present invention is directed to a novel magnesium composite for use as a dissolvable component in oil drilling and will be described with particular reference to such application. As can be appreciated, the novel magnesium composite of the present invention can be used in other applications (e.g., non-oil wells, etc.). In one non-limiting embodiment, the present invention is directed to a ball or other tool component in a well drilling or completion operation such as, but not limited to, a component that is seated in a hydraulic operation that can be dissolved away after use so that no drilling or removal of the component is necessary. Tubes, valves, valve components, plugs, frac balls, sleeve, hydraulic actuating tooling, mandrels, slips, grips, balls, darts, carriers, valve components, other downhole well components and other shapes of components can also be formed of the novel magnesium composite of the present invention. For purposes of this invention, primary dissolution is measured for valve components and plugs as the time the part removes itself from the seat of a valve or plug arrangement or can become free floating in the system. For example, when the part is a plug in a plug system, primary dissolution occurs when the plug has degraded or dissolved to a point that it can no long function as a plug and thereby allows fluid to flow about the plug. For purposes of this invention, secondary dissolution is measured in the time the part is fully dissolved into submicron particles. As can be appreciated, the novel magnesium composite of the present invention can be used in other well components that also desire the function of dissolving after a period of time. In one non-limiting aspect of the present invention, a galvanically-active phase is precipitated from the novel magnesium composite composition and is used to control the dissolution rate of the component; however, this is not required. The novel magnesium composite is generally castable and/or machinable and can be used in place of existing metallic or plastic components in oil and gas drilling rigs including, but not limited to, water injection and hydraulic fracturing. The novel magnesium composite can be heat treated as well as extruded and/or forged.
In one non-limiting aspect of the present invention, the novel magnesium composite is used to form a castable, moldable, or extrudable component. Non-limiting magnesium composites in accordance with the present invention include at least 50 wt. % magnesium. One or more additives are added to a magnesium or magnesium alloy to form the novel magnesium composite of the present invention. The one or more additives can be selected and used in quantities so that galvanically-active intermetallic or insoluble precipitates form in the magnesium or magnesium alloy while the magnesium or magnesium alloy is in a molten state and/or during the cooling of the melt; however, this is not required. The one or more additives can be in the form of a pure or nearly pure additive element (e.g., at least 98% pure), or can be added as an alloy of two or more additive elements or an alloy of magnesium and one or more additive elements. The one or more additives typically are added in a weight percent that is less than a weight percent of said magnesium or magnesium alloy. Typically, the magnesium or magnesium alloy constitutes about 50.1-99.9 wt. % of the magnesium composite and all values and ranges therebetween. In one non-limiting aspect of the invention, the magnesium or magnesium alloy constitutes about 60-95 wt. % of the magnesium composite, and typically the magnesium or magnesium alloy constitutes about 70-90 wt. % of the magnesium composite. The one or more additives can be added to the molten magnesium or magnesium alloy at a temperature that is less than the melting point of the one or more additives; however, this is not required. The one or more additives generally have an average particle diameter size of at least about 0.1 microns, typically no more than about 500 microns (e.g., 0.1 microns, 0.1001 microns, 0.1002 microns . . . 499.9998 microns, 499.9999 microns, 500 microns) and include any value or range therebetween, more typically about 0.1-400 microns, and still more typically about 10-50 microns. In one non-limiting configuration, the particles can be less than 1 micron. During the process of mixing the one or more additives in the molten magnesium or magnesium alloy, the one or more additives do not typically fully melt in the molten magnesium or magnesium alloy; however, the one or more additives can form a single-phase liquid with the magnesium while the mixture is in the molten state. As can be appreciated, the one or more additives can be added to the molten magnesium or magnesium alloy at a temperature that is greater than the melting point of the one or more additives. The one or more additives can be added individually as pure or substantially pure additive elements or can be added as an alloy that is formed of a plurality of additive elements and/or an alloy that includes one or more additive elements and magnesium. When one or more additive elements are added as an alloy, the melting point of the alloy may be less than the melting point of one or more of the additive elements that are used to form the alloy; however, this is not required. As such, the addition of an alloy of the one or more additive elements could be caused to melt when added to the molten magnesium at a certain temperature, whereas if the same additive elements were individually added to the molten magnesium at the same temperature, such individual additive elements would not fully melt in the molten magnesium.
The one or more additives are selected such that as the molten magnesium cools, newly formed metallic alloys and/or additives begin to precipitate out of the molten metal and form the in situ phase to the matrix phase in the cooled and solid magnesium composite. After the mixing process is completed, the molten magnesium or magnesium alloy and the one or more additives that are mixed in the molten magnesium or magnesium alloy are cooled to form a solid component. In one non-limiting embodiment, the temperature of the molten magnesium or magnesium alloy is at least about 10° C. less than the melting point of the additive that is added to the molten magnesium or magnesium alloy during the addition and mixing process, typically at least about 100° C. less than the melting point of the additive that is added to the molten magnesium or magnesium alloy during the addition and mixing process, more typically about 100-1000° C. (and any value or range therebetween) less than the melting point of the additive that is added to the molten magnesium or magnesium alloy during the addition and mixing process; however, this is not required. As can be appreciated, one or more additives in the form of an alloy or a pure or substantially pure additive element can be added to the magnesium that have a melting point that is less than the melting point of magnesium, but still at least partially precipitate out of the magnesium as the magnesium cools from its molten state to a solid state. Generally, such one or more additives and/or one or more components of the additives form an alloy with the magnesium and/or one or more other additives in the molten magnesium. The formed alloy has a melting point that is greater than a melting point of magnesium, thereby results in the precipitation of such formed alloy during the cooling of the magnesium from the molten state to the solid state. The never melted additive(s) and/or the newly formed alloys that include one or more additives are referred to as in situ particle formation in the molten magnesium composite. Such a process can be used to achieve a specific galvanic corrosion rate in the entire magnesium composite and/or along the grain boundaries of the magnesium composite.
The invention adopts a feature that is usually a negative in traditional casting practices wherein a particle is formed during the melt processing that corrodes the alloy when exposed to conductive fluids and is imbedded in eutectic phases, the grain boundaries, and/or even within grains with precipitation hardening. This feature results in the ability to control where the galvanically-active phases are located in the final casting, as well as the surface area ratio of the in situ phase to the matrix phase, which enables the use of lower cathode phase loadings as compared to a powder metallurgical or alloyed composite to achieve the same dissolution rates. The in situ formed galvanic additives can be used to enhance mechanical properties of the magnesium composite such as ductility, tensile strength, and/or shear strength. The final magnesium composite can also be enhanced by heat treatment as well as deformation processing (such as extrusion, forging, or rolling) to further improve the strength of the final composite over the as-cast material; however, this is not required. The deformation processing can be used to achieve strengthening of the magnesium composite by reducing the grain size of the magnesium composite. Further enhancements, such as traditional alloy heat treatments (such as solutionizing, aging and/or cold working) can be used to enable control of dissolution rates through precipitation of more or less galvanically-active phases within the alloy microstructure while improving mechanical properties; however, this is not required. Because galvanic corrosion is driven by both the electro potential between the anode and cathode phase, as well as the exposed surface area of the two phases, the rate of corrosion can also be controlled through adjustment of the in situ formed particle size, while not increasing or decreasing the volume or weight fraction of the addition, and/or by changing the volume/weight fraction without changing the particle size. Achievement of in situ particle size control can be achieved by mechanical agitation of the melt, ultrasonic processing of the melt, controlling cooling rates, and/or by performing heat treatments. In situ particle size can also or alternatively be modified by secondary processing such as rolling, forging, extrusion and/or other deformation techniques.
In another non-limiting aspect of the invention, a cast structure can be made into almost any shape. During formation, the active galvanically-active in situ phases can be uniformly dispersed throughout the component and the grain or the grain boundary composition can be modified to achieve the desired dissolution rate. The galvanic corrosion can be engineered to affect only the grain boundaries and/or can affect the grains as well (based on composition); however, this is not required. This feature can be used to enable fast dissolutions of high-strength lightweight alloy composites with significantly less active (cathode) in situ phases as compared to other processes.
In yet another and/or alternative non-limiting aspect of the invention, the in situ formed particles can act as matrix strengtheners to further increase the tensile strength of the material compared to the base alloy without the one or more additives; however, this is not required.
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a method of controlling the dissolution properties of a metal selected from the class of magnesium and/or magnesium alloy comprising of the steps of a) melting the magnesium or magnesium alloy to a point above its solidus, b) introducing one or more additives to the magnesium or magnesium alloy in order to achieve in situ precipitation of galvanically-active intermetallic phases, and c) cooling the melt to a solid form. The one or more additives are generally added to the magnesium or magnesium alloy when the magnesium or magnesium alloy is in a molten state and at a temperature that is less than the melting point of one or more additive materials. As can be appreciated, one or more additives can be added to the molten magnesium or magnesium alloy at a temperature that is greater than the melting point of the one or more additives. The one or more additives can be added as individual additive elements to the magnesium or magnesium alloy, or be added in alloy form as an alloy of two or more additives, or an alloy of one or more additives and magnesium or magnesium alloy. The galvanically-active intermetallic phases can be used to enhance the yield strength of the alloy; however, this is not required. The size of the in situ precipitated intermetallic phase can be controlled by a melt mixing technique and/or cooling rate; however, this is not required. It has been found that the addition of the one or more additives (SM) to the molten magnesium or magnesium alloy can result in the formation of MgSM_x, Mg_xSM, and LPSO and other phases with two, three, or even four components that include one or more galvanically-active additives that result in the controlled degradation of the formed magnesium composite when exposed to certain environments (e.g., salt water, brine, fracking liquids, etc.). The method can include the additional step of subjecting the magnesium composite to intermetallic precipitates to solutionizing of at least about 300° C. to improve tensile strength and/or improve ductility; however, this is not required. The solutionizing temperature is less than the melting point of the magnesium composite. Generally, the solutionizing temperature is less than 50-200° C. of the melting point of the magnesium composite and the time period of solutionizing is at least 0.1 hours. In one non-limiting aspect of the invention, the magnesium composite can be subjected to a solutionizing temperature for about 0.5-50 hours (and all values and ranges therebetween) (e.g., 1-15 hours, etc.) at a temperature of 300-620° C. (and all values and ranges therebetween) (e.g., 300-500° C., etc.). The method can include the additional step of subjecting the magnesium composite to intermetallic precipitates and to artificially age the magnesium composite at a temperature at least about 90° C. to improve the tensile strength; however, this is not required. The artificial aging process temperature is typically less than the solutionizing temperature and the time period of the artificial aging process temperature is typically at least 0.1 hours. Generally, the artificial aging process is less than 50-400° C. (the solutionizing temperature). In one non-limiting aspect of the invention, the magnesium composite can be subjected to the artificial aging process for about 0.5-50 hours (and all values and ranges therebetween) (e.g., 1-16 hours, etc.) at a temperature of 90-300° C. (and all values and ranges therebetween) (e.g., 100-200° C.).
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that is over 50 wt. % magnesium and about 0.5-49.5 wt. % of additive (SM) (e.g., aluminum, zinc, tin, beryllium, boron carbide, copper, nickel, bismuth, cobalt, titanium, manganese, potassium, sodium, antimony, indium, strontium, barium, silicon, lithium, silver, gold, cesium, gallium, calcium, iron, lead, mercury, arsenic, rare earth metals (e.g., yttrium, lanthanum, samarium, europium, gadolinium, terbium, dysprosium, holmium, ytterbium, etc.) and zirconium) (and all values and ranges therebetween) is added to the magnesium or magnesium alloy to form a galvanically-active intermetallic particle. The one or more additives can be added to the magnesium or magnesium alloy while the temperature of the molten magnesium or magnesium alloy is less than or greater than the melting point of the one or more additives. In one non-limiting embodiment, throughout the mixing process, the temperature of the molten magnesium or magnesium alloy can be less than the melting point of the one or more additives.
In another non-limiting embodiment, throughout the mixing process, the temperature of the molten magnesium or magnesium alloy can be less than the melting point of the alloy that includes one or more additives. During the mixing process, solid particles of SMMg_x, SM_xMg can be formed. Once the mixing process is complete, the mixture of molten magnesium or magnesium alloy, SMMg_x, SM_xMg, and/or any unalloyed additive is cooled and an in situ precipitate is formed in the solid magnesium composite.
In another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that is over 50 wt. % magnesium and about 0.05-49.5 wt. % nickel (and all values or ranges therebetween) is added to the magnesium or magnesium alloy to form intermetallic Mg₂Ni as a galvanically-active in situ precipitate. In one non-limiting arrangement, the magnesium composite includes about 0.05-23.5 wt. % nickel, 0.01-5 wt. % nickel, 3-7 wt. % nickel, 7-10 wt. % nickel, or 10-24.5 wt. % nickel. The nickel is added to the magnesium or magnesium alloy while the temperature of the molten magnesium or magnesium alloy is less than the melting point of the nickel; however, this is not required. In one non-limiting embodiment, throughout the mixing process, the temperature of the molten magnesium or magnesium alloy is less than the melting point of the nickel. During the mixing process, solid particles of Mg₂Ni can be formed; but is not required. Once the mixing process is complete, the mixture of molten magnesium or magnesium alloy, any solid particles of Mg₂Ni, and any unalloyed nickel particles are cooled and an in situ precipitate of any solid particles of Mg₂Ni and any unalloyed nickel particles is formed in the solid magnesium composite. Generally, the temperature of the molten magnesium or magnesium alloy is at least about 200° C. less than the melting point of the nickel added to the molten magnesium or magnesium alloy during the addition and mixing process; however, it is not required.
In still another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that is over 50 wt. % magnesium and about 0.05-49.5 wt. % copper (and all values or ranges therebetween) is added to the magnesium or magnesium alloy to form galvanically-active in situ precipitate that includes copper and/or copper alloy. In one non-limiting arrangement, the magnesium composite includes about 0.01-5 wt. % copper, about 0.5-15 wt. % copper, about 15-35 wt. % copper, or about 0.01-20 wt. % copper. The copper is added to the magnesium or magnesium alloy while the temperature of the molten magnesium or magnesium alloy is less than the melting point of the copper; however, this is not required. In one non-limiting embodiment, throughout the mixing process, the temperature of the molten magnesium or magnesium alloy is less than the melting point of the copper; however, this is not required. During the mixing process, solid particles of CuMg₂can be formed; but is not required. Once the mixing process is complete, the mixture of molten magnesium or magnesium alloy, any solid particles of CuMg₂, and any unalloyed copper particles are cooled and an in situ precipitate of any solid particles of CuMg₂and any unalloyed copper particles is formed in the solid magnesium composite. Generally, the temperature of the molten magnesium or magnesium alloy is at least about 200° C. less than the melting point of the copper added to the molten magnesium or magnesium alloy; however, this is not required.
In another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that is over 50 wt. % magnesium and up to about 49.5% by weight tin (and all values and ranges therebetween) is added to the magnesium or magnesium alloy to form galvanically-active in situ precipitate that includes tin and/or tin alloy. Tin additions have a significant solubility in solid magnesium at elevated temperatures, forming both a eutectic (at grain boundaries), as well as in the primary magnesium (dispersed). Dispersed precipitates, which can be controlled by heat treatment, lead to large strengthening, while eutectic phases are particularly effective at initiating accelerated corrosion rates.
In general, precipitates having an electronegativity greater than 1.4-1.5 act as corrosion acceleration points, and are more effective if formed from the eutectic liquid during solidification, than precipitation from a solid solution. Alloying additions added below their solid solubility limit which precipitate in the primary magnesium phase during solidification (as opposed to along grain boundaries), and which can be solutionized are more effective in creating higher strength, particularly in as-cast alloys.
In another and/or alternative non-limiting aspect of the invention, the molten magnesium or magnesium alloy that includes the one or more additives can be controllably cooled to form the in situ precipitate in the solid magnesium composite. In one non-limiting embodiment, the molten magnesium or magnesium alloy that includes the one or more additives is cooled at a rate of greater than 1° C. per minute. In one non-limiting embodiment, the molten magnesium or magnesium alloy that includes the one or more additives is cooled at a rate of less than 1° C. per minute. In one non-limiting embodiment, the molten magnesium or magnesium alloy that includes the one or more additives is cooled at a rate of greater than 0.01° C. per min and slower than 1° C. per minute. In one non-limiting embodiment, the molten magnesium or magnesium alloy that includes the one or more additives is cooled at a rate of greater than 10° C. per minute and less than 100° C. per minute. In one non-limiting embodiment, the molten magnesium or magnesium alloy that includes the one or more additives is cooled at a rate of less than 10° C. per minute. In another non-limiting embodiment, the molten magnesium or magnesium alloy that includes the one or more additives is cooled at a rate 10-100° C./min (and all values and ranges therebetween) through the solidus temperature of the alloy to form fine grains in the alloy.
In another and/or alternative non-limiting aspect of the invention, there is provided a magnesium alloy that includes over 50 wt. % magnesium (e.g., 50.01-99.99 wt. % and all values and ranges therebetween) and includes at least one metal selected from the group consisting of aluminum, boron, bismuth, zinc, zirconium, and manganese. As can be appreciated, the magnesium alloy can include one or more additional metals. In one non-limiting embodiment, the magnesium alloy includes over 50 wt. % magnesium and includes at least one metal selected from the group consisting of aluminum in an amount of about 0.05-10 wt. % (and all values and ranges therebetween), zinc in amount of about 0.05-6 wt. % (and all values and ranges therebetween), zirconium in an amount of about 0.01-3 wt. % (and all values and ranges therebetween), and/or manganese in an amount of about 0.015-2 wt. % (and all values and ranges therebetween). In another non-limiting formulation, the magnesium alloy includes over 50 wt. % magnesium and includes at least one metal selected from the group consisting of zinc in amount of about 0.05-6 wt. %, zirconium in an amount of about 0.05-3 wt. %, manganese in an amount of about 0.05-0.25 wt. %, boron (optionally) in an amount of about 0.0002-0.04 wt. %, and bismuth (optionally) in an amount of about 0.4-0.7 wt. %. In still another and/or alternative non-limiting aspect of the invention, there is provided a magnesium alloy that is over 50 wt. % magnesium and at least one metal selected from the group consisting of aluminum in an amount of about 0.05-10 wt. % (and all values and ranges therebetween), zinc in an amount of about 0.05-6 wt. % (and all values and ranges therebetween), calcium in an amount of about 0.5-8 wt. %% (and all values and ranges therebetween), zirconium in amount of about 0.05-3 wt. % (and all values and ranges therebetween), manganese in an amount of about 0.05-0.25 wt. % (and all values and ranges therebetween), boron in an amount of about 0.0002-0.04 wt. % (and all values and ranges therebetween), and/or bismuth in an amount of about 0.04-0.7 wt. % (and all values and ranges therebetween).
In still another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that is over 50 wt. % magnesium and includes one or more additives in the form of a first additive that has an electronegativity that is greater than 1.5, and typically greater than 1.8. The electronegativity of magnesium is 1.31. As such, the first additive has a higher electronegativity than magnesium. The first additive can include one or more metals selected from the group consisting of nickel (1.91), cobalt (1.88), copper (1.90), bismuth (2.02), lead (1.87), tin (1.96), antimony (2.05), indium (1.78), silver (1.93), gold (2.54), and gallium (1.81). It has been found that by adding one or more first additives to a molten magnesium or molten magnesium alloy, galvanically-active phases can be formed in the solid magnesium composite having desired dissolution rates in salt water, fracking liquid or brine environments. The one or more first additives are added to the molten magnesium or molten magnesium alloy such that the final magnesium composite includes 0.05-49.55% by weight of the one or more first additives (and all values and ranges therebetween), and typically 0.5-35% by weight of the one or more first additives. The one or more first additives having an electronegativity that is greater than 1.5 have been found to form galvanically-active phases in the solid magnesium composite to enhance the dissolution rate of the magnesium composite in salt water, fracking liquid or brine environments.
In yet another and/or alternative non-limiting aspect of the invention, it has been found that in addition to the adding of one or more first additives having an electronegativity that is greater than 1.5 to the molten magnesium or molten magnesium alloy to enhance the dissolution rates of the magnesium composite in salt water, fracking liquid or brine environments, one or more second additives that have an electronegativity of 1.25 or less can also be added to the molten magnesium or molten magnesium alloy to further enhance the dissolution rates of the solid magnesium composite. The one or more second additives can optionally be added to the molten magnesium or molten magnesium alloy such that the final magnesium composite includes 0.05-35% by weight of the one or more second additives (and all values and ranges therebetween), and typically 0.5-30% by weight of the one or more second additives. The second additive can include one or more metals selected from the group consisting of calcium (1.0), strontium (0.95), barium (0.89), potassium (0.82), sodium (0.93), lithium (0.98), cesium (0.79), and the rare earth metals such as yttrium (1.22), lanthanum (1.1), samarium (1.17), europium (1.2), gadolinium (1.2), terbium (1.1), dysprosium (1.22), holmium (1.23), and ytterbium (1.1).
Secondary additives are usually added at 0.5-10 wt. %, and generally 0.1-3 wt. %. In one non-limiting embodiment, the amount of secondary additive is less than the primary additive; however, this is not required. For example, calcium can be added up to 10 wt. %, but is added normally at 0.5-3 wt. %. In most cases, the strengthening alloying additions or modifying materials are added in concentrations which can be greater than the high electronegativity corrosive phase forming element. The secondary additions are generally designed to have high solubility, and are added below their solid solubility limit in magnesium at the melting point, but above their solid solubility limit at some lower temperature. These form precipitates that strengthen the magnesium, and may or may not be galvanically active. They may form a precipitate by reacting preferentially with the high electronegativity addition (e.g., binary, ternary, or even quaternary intermetallics), with magnesium, or with other alloying additions.
Secondary additives are usually added at 0.5-10 wt. %, and generally 0.1-3 wt. %. In one non-limiting embodiment, the amount of secondary additive is less than the primary additive; however, this is not required. For example, calcium can be added up to 10 wt. %, but is added normally at 0.5-3 wt. %. In most cases, the strengthening alloying additions or modifying materials are added in concentrations which can be greater than the high electronegativity corrosive phase forming element. The secondary additions are generally designed to have high solubility, and are added below their solid solubility limit in magnesium at the melting point, but above their solid solubility limit at some lower temperature. These form precipitates that strengthen the magnesium, and may or may not be galvanically active. They may form a precipitate by reacting preferentially with the high electronegativity addition (e.g., binary, ternary, or even quaternary intermetallics), with magnesium, or with other alloying additions.
The one or more secondary additives that have an electronegativity that is 1.25 or less have been found to form galvanically-active phases in the solid magnesium composite to enhance the dissolution rate of the magnesium composite in salt water, fracking liquid or brine environments are. The inclusion of the one or more second additives with the one or more first additives in the molten magnesium or magnesium alloy has been found to enhance the dissolution rate of the magnesium composite by 1) alloying with inhibiting aluminum, zinc, magnesium, alloying additions and increasing the EMF driving force with the galvanically-active phase, and/or 2) reducing the electronegativity of the magnesium (e.g., α-magnesium) phase when placed in solid solution or magnesium-EPE (electropositive element) intermetallics. The addition of materials with an electronegativity that is less than magnesium, such as rare earths, group 1, and group II, and group III elements on the periodic table, can enhance the degradability of the alloy when a high electronegativity addition is also present by reducing the electronegativity (increasing the driving force) in solid solution in magnesium, and/or by forming lower electronegativity precipitates that interact with the higher electronegativity precipitates. This technique/additions is particularly effective at reducing the sensitivity of the corrosion rates to temperature or salt content of the corroding or downhole fluid.
The addition of both electropositive (1.5 or greater) first additives and electronegative (1.25 or less) second additives to the molten magnesium or magnesium alloy can result in higher melting phases being formed in the magnesium composite. These higher melting phases can create high melt viscosities and can dramatically increase the temperature (and therefore the energy input) required to form the low viscosity melts suitable for casting. By dramatically increasing the casting temperature to above 700-780° C., or utilizing pressure to drive mold filling (e.g., squeeze casting), such processes can be used to produce a high quality, low-inclusion and low-porosity magnesium composite casting.
In yet another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that is subjected to heat treatments such as solutionizing, aging and/or cold working to be used to control dissolution rates through precipitation of more or less galvanically-active phases within the alloy microstructure while improving mechanical properties. The artificial aging process (when used) can be for at least about 1 hour, for about 1-50 hours (and all values and ranges therebetween), for about 1-20 hours, or for about 8-20 hours. The solutionizing (when used) can be for at least about 1 hour, for about 1-50 hours (and all values and ranges therebetween), for about 1-20 hours, or for about 8-20 hours. When an alloy with a galvanically-active phase (higher and/or lower electronegativity than Mg) with significant solid solubility is solutionized, substantial differences in corrosion/degradation rates can be achieved through mechanisms of oswald ripening or grain growth (coarsening of the active phases), which increases corrosion rates by 10-100% (and all values and ranges therebewteen). When the solutionizing removes active phase and places it in solid solution, or creates finer precipitates (refined grain sizes), corrosion rates are decreased by 10-50%, up to about 75%.
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a method for controlling the dissolution rate of the magnesium composite wherein the magnesium content is at least about 75% and at least about 0.05 wt. % nickel is added to form in situ precipitation in the magnesium or magnesium alloy and solutionizing the resultant metal at a temperature within a range of 100-500° C. (and all values and ranges therebetween) for a period of 0.25-50 hours (and all values and ranges therebetween), the magnesium composite being characterized by higher dissolution rates than metal without nickel additions subjected to the said artificial aging process.
In another and/or alternative non-limiting aspect of the invention, there is provided a method for improving the physical properties of the magnesium composite wherein the magnesium content is at least about 85% and at least about 0.05 wt. % nickel is added to form in situ precipitation in the magnesium or magnesium alloy and solutionizing the resultant metal at a temperature at about 100-500° C. (and all values and ranges therebetween) for a period of 0.25-50 hours, the magnesium composite being characterized by higher tensile and yield strengths than magnesium base alloys of the same composition, not including the amount of nickel.
In still another and/or alternative non-limiting aspect of the invention, there is provided a method for controlling the dissolution rate of the magnesium composite wherein the magnesium content in the alloy is at least about 75% and at least about 0.05 wt. % copper is added to form in situ precipitation in the magnesium or magnesium alloy and solutionizing the resultant metal at a temperature within a range of 100-500° C. for a period of 0.25-50 hours, the magnesium composite being characterized by higher dissolution rates than metal without copper additions subjected to the said artificial aging process.
In yet another and/or alternative non-limiting aspect of the invention, there is provided a method for improving the physical properties of the magnesium composite wherein the total content of magnesium in the magnesium or magnesium alloy is at least about 85 wt. % and copper is added to form in situ precipitation in the magnesium or magnesium composite and solutionizing the resultant metal at a temperature of about 100-500° C. for a period of 0.25-50 hours. The magnesium composite is characterized by higher tensile and yield strengths than magnesium-based alloys of the same composition, but not including the amount of copper.
In yet another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that is subjected to heat treatments such as solutionizing, aging and/or cold working to be used to control dissolution rates though precipitation of more or less galvanically-active phases within the alloy microstructure while improving mechanical properties. The artificial aging process (when used) can be for at least about 1 hour, for about 1-50 hours, for about 1-20 hours, or for about 8-20 hours. The solutionizing (when used) can be for at least about 1 hour, for about 1-50 hours, for about 1-20 hours, or for about 8-20 hours.
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a method for controlling the dissolution rate of the magnesium composite wherein the magnesium content is at least about 75 wt. % and at least 0.05 wt. % nickel is added to form in situ precipitation in the magnesium or magnesium alloy and solutionizing the resultant metal at a temperature within a range of 100-500° C. for a period of 0.25-50 hours, the magnesium composite being characterized by higher dissolution rates than metal without nickel additions subjected to the said artificial aging process.
In another and/or alternative non-limiting aspect of the invention, there is provided a method for improving the physical properties of the magnesium composite wherein the magnesium content is at least about 85 wt. % and at least 0.05 wt. % nickel is added to form in situ precipitation in the magnesium or magnesium alloy and solutionizing the resultant metal at a temperature at about 100-500° C. for a period of 0.25-50 hours, the magnesium composite being characterized by higher tensile and yield strengths than magnesium base alloys of the same composition, but not including the amount of nickel.
In still another and/or alternative non-limiting aspect of the invention, there is provided a method for controlling the dissolution rate of the magnesium composite wherein the magnesium content in the alloy is at least about 75 wt. % and at least 0.05 wt. % copper added to form in situ precipitation in the magnesium or magnesium alloy and solutionizing the resultant metal at a temperature within a range of 100-500° C. for a period of 0.25-50 hours, the magnesium composite being characterized by higher dissolution rates than metal without copper additions subjected to the said artificial aging process.
In yet another and/or alternative non-limiting aspect of the invention, there is provided a method for improving the physical properties of the magnesium composite wherein the total content of magnesium in the magnesium or magnesium alloy is at least about 85 wt. % and at least 0.05 wt. % copper is added to form in situ precipitation in the magnesium or magnesium composite and solutionizing the resultant metal at a temperature of about 100-500° C. for a period of 0.25-50 hours, the magnesium composite being characterized by higher tensile and yield strengths than magnesium base alloys of the same composition, but not including the amount of copper.
In still another and/or alternative non-limiting aspect of the invention, the additive generally has a solubility in the molten magnesium or magnesium alloy of less than about 10% (e.g., 0.01-9.99% and all values and ranges therebetween), typically less than about 5%, more typically less than about 1%, and even more typically less than about 0.5%.
In still another and/or alternative non-limiting aspect of the invention, the additive can optionally have a surface area of 0.001-200 m²/g (and all values and ranges therebetween). The additive in the magnesium composite can optionally be less than about 1 μm in size (e.g., 0.001-0.999 μm and all values and ranges therebetween), typically less than about 0.5 μm, more typically less than about 0.1 μm, and more typically less than about 0.05 μm. The additive can optionally be dispersed throughout the molten magnesium or magnesium alloy using ultrasonic means, electrowetting of the insoluble particles, and/or mechanical agitation. In one non-limiting embodiment, the molten magnesium or magnesium alloy is subjected to ultrasonic vibration and/or waves to facilitate in the dispersion of the additive in the molten magnesium or magnesium alloy.
In still yet another and/or alternative non-limiting aspect of the invention, a plurality of additives in the magnesium composite are located in grain boundary layers of the magnesium composite.
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a method for forming a magnesium composite that includes a) providing magnesium or a magnesium alloy, b) providing one or more additives that have a low solubility when added to magnesium or a magnesium alloy when in a molten state; c) mixing the magnesium or a magnesium alloy and the one or more additives to form a mixture and to cause the one or more additives to disperse in the mixture; and d) cooling the mixture to form the magnesium composite. The step of mixing optionally includes mixing using one or more processes selected from the group consisting of thixomolding, stir casting, mechanical agitation, electrowetting and ultrasonic dispersion. The method optionally includes the step of heat treating the magnesium composite to improve the tensile strength, elongation, or combinations thereof of the magnesium composite without significantly affecting a dissolution rate of the magnesium composite. The method optionally includes the step of extruding or deforming the magnesium composite to improve the tensile strength, elongation, or combinations thereof of the magnesium composite without significantly affecting a dissolution rate of the magnesium composite. The method optionally includes the step of forming the magnesium composite into a device that a) facilitates in separating hydraulic fracturing systems and zones for oil and gas drilling, b) provides structural support or component isolation in oil and gas drilling and completion systems, or c) is in the form of a frac ball, valve, or degradable component of a well composition tool or other tool. Other types of structures that the magnesium composite can be partially or fully formed into include, but are not limited to, sleeves, valves, hydraulic actuating tooling and the like.
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that has a dissolve rate or dissolution rate of at least about 30 mg/cm²-hr in 3% KCl solution at 90° C., and typically 30-500 mg/cm²-hr in 3% KCl solution at 90° C. (and all values and ranges therebetween).
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that has a dissolve rate or dissolution rate of at least about 0.2 mg/cm²-min in a 3% KCl solution at 90° C., and typically 0.2-150 mg/cm²-min in a 3% KCl solution at 90° C. (and all values and ranges therebetween).
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that has a dissolve rate or dissolution rate of at least about 0.1 mg/cm²-hr in a 3% KCl solution at 21° C., and typically 0.1-5 mg/cm²-hr in a 3% KCl solution at 21° C. (and all values and ranges therebetween).
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that has a dissolve rate or dissolution rate of at least about 0.2 mg/cm²-min in a 3% KCl solution at 20° C.
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that has a dissolve rate or dissolution rate of at least about 0.1 mg/cm²-hr in 3% KCl solution at 20° C., typically 0.1-5 mg/cm²-hr in a 3% KCl solution at 20° C. (and all values and ranges therebetween).
In still yet another and/or alternative non-limiting aspect of the invention, there is provided a magnesium composite that has a dissolve rate or dissolution rate of at least about 0.1 mg/cm²-hr in 3% KCl solution at 20° C., typically 0.1-5 mg/cm²-hr in a 3% KCl solution at 20° C. (and all values and ranges therebetween).
In still another and/or alternative non-limiting aspect of the invention, there is provided a method for controlling the dissolution properties of a magnesium or a magnesium alloy comprising of the steps of: a) heating the magnesium or a magnesium alloy to a point above its solidus temperature; b) adding an additive to said magnesium or magnesium alloy while said magnesium or magnesium alloy is above said solidus temperature of magnesium or magnesium alloy to form a mixture, said additive including one or more first additives having an electronegativity of greater than 1.5, said additive constituting about 0.05-45 wt. % of said mixture; c) dispersing said additive in said mixture while said magnesium or magnesium alloy is above said solidus temperature of magnesium or magnesium alloy; and, d) cooling said mixture to form a magnesium composite, said magnesium composite including in situ precipitation of galvanically-active intermetallic phases. The first additive can optionally have an electronegativity of greater than 1.8. The step of controlling a size of said in situ precipitated intermetallic phase can optionally be by controlled selection of a mixing technique during said dispersion step, controlling a cooling rate of said mixture, or combinations thereof. The magnesium or magnesium alloy can optionally be heated to a temperature that is less than said melting point temperature of at least one of said additives. The magnesium or magnesium alloy can be heated to a temperature that is greater than said melting point temperature of at least one of said additives. The additive can optionally include one or more metals selected from the group consisting of calcium, copper, nickel, cobalt, bismuth, silver, gold, lead, tin, antimony, indium, arsenic, mercury, and gallium. The additive can optionally include one or more metals selected from the group consisting of calcium, copper, nickel, cobalt, bismuth, tin, antimony, indium, and gallium. The additive can optionally include one or more second additives that have an electronegativity of less than 1.25. The second additive can optionally include one or more metals selected from the group consisting of strontium, barium, potassium, sodium, lithium, cesium, and the rare earth metals such as yttrium, lanthanum, samarium, europium, gadolinium, terbium, dysprosium, holmium, and ytterbium. The additive can optionally be formed of a single composition, and has an average particle diameter size of about 0.1-500 microns. At least a portion of said additive can optionally remain at least partially in solution in an α-magnesium phase of said magnesium composite. The magnesium alloy can optionally include over 50 wt. % magnesium and one or more metals selected from the group consisting of aluminum, boron, bismuth, zinc, zirconium, and manganese. The magnesium alloy can optionally include over 50 wt. % magnesium and one or more metals selected from the group consisting of aluminum in an amount of about 0.5-10 wt. %, zinc in amount of about 0.1-6 wt. %, zirconium in an amount of about 0.01-3 wt. %, manganese in an amount of about 0.15-2 wt. %; boron in amount of about 0.0002-0.04 wt. %, and bismuth in amount of about 0.4-0.7 wt. %. The magnesium alloy can optionally include over 50 wt. % magnesium and one or more metals selected from the group consisting of aluminum in an amount of about 0.5-10 wt. %, zinc in amount of about 0.1-3 wt. %, zirconium in an amount of about 0.01-1 wt. %, manganese in an amount of about 0.15-2 wt. %; boron in amount of about 0.0002-0.04 wt. %, and bismuth in amount of about 0.4-0.7. wt %. The step of solutionizing said magnesium composite can optionally occur at a temperature above 300° C. and below a melting temperature of said magnesium composite to improve tensile strength, ductility, or combinations thereof of said magnesium composite. The step of forming said magnesium composite into a final shape or near net shape can optionally be by a) sand casting, permanent mold casting, investment casting, shell molding, or other pressureless casting technique at a temperature above 730° C., 2) using either pressure addition or elevated pouring temperatures above 710° C., or 3) subjecting the magnesium composite to pressures of 2000-20,000 psi through the use of squeeze casting, thixomolding, or high pressure die casting techniques. The step of aging said magnesium composite can optionally be at a temperature of above 100° C. and below 300° C. to improve tensile strength of said magnesium composite. The magnesium composite can optionally have a hardness above 14 Rockwell Harness B. The magnesium composite can optionally have a dissolution rate of at least 5 mg/cm²-hr. in 3% KCl at 90° C. The additive metal can optionally include about 0.05-35 wt. % nickel. The additive can optionally include about 0.05-35 wt. % copper. The additive can optionally include about 0.05-35 wt. % antimony. The additive can optionally include about 0.05-35 wt. % gallium. The additive can optionally include about 0.05-35 wt. % tin. The additive can optionally include about 0.05-35 wt. % bismuth. The additive can optionally include about 0.05-35 wt. % calcium. The method can optionally further include the step of rapidly solidifying said magnesium composite by atomizing the molten mixture and then subjecting the atomized molten mixture to ribbon casting, gas and water atomization, pouring into a liquid, high speed machining, saw cutting, or grinding into chips, followed by powder or chip consolidation below its liquidus temperature.
In still another and/or alternative non-limiting aspect of the invention, there is provided a degradable alloy wherein the galvanically active phase is optionally present in the form of an LPSO (Long Period Stacking Fault) phase such as Mg₁₂Zn₁-xNi_xRE (where RE is a rare earth element) and that phase is 0.05-5 wt. % of the final alloy composition.
In still another and/or alternative non-limiting aspect of the invention, there is provided a degradable alloy wherein the mechanical properties at 150° C. are optionally at least 24 ksi tensile yield strength, and are not less than 20% lower than the mechanical properties at room temperature (77° F.).
In still another and/or alternative non-limiting aspect of the invention, there is provided a degradable alloy can optionally be formed at double the speed or higher as compared to an alloy that does not include calcium due to the rise in incipient melting temperature.
Another and/or alternative non-limiting objective of the present invention is the provision of selecting the type and quantity of one or more additives so that the grain boundaries of the magnesium composite have a desired composition and/or morphology to achieve a specific galvanic corrosion rate in the entire magnesium composite and/or along the grain boundaries of the magnesium composite.
Still yet another and/or alternative non-limiting objective of the present invention is the provision of forming a magnesium composite wherein the one or more additives can be used to enhance mechanical properties of the magnesium composite, such as ductility and/or tensile strength.
Another and/or alternative non-limiting objective of the present invention is the provision of forming a magnesium composite that can be enhanced by heat treatment as well as deformation processing, such as extrusion, forging, or rolling, to further improve the strength of the final magnesium composite.
Another and/or alternative non-limiting objective of the present invention is the provision of dispersing the one or more additives in the molten magnesium or magnesium alloy is at least partially by thixomolding, stir casting, mechanical agitation, electrowetting, ultrasonic dispersion and/or combinations of these processes.
Another and/or alternative non-limiting objective of the present invention is the provision of producing a magnesium composite with at least one insoluble phase that is at least partially formed by the additive or additive material, and wherein the one or more additives have a different galvanic potential from the magnesium or magnesium alloy.
Still yet another and/or alternative non-limiting objective of the present invention is the provision of producing a magnesium composite wherein the rate of corrosion in the magnesium composite can be controlled by the surface area via the particle size and morphology of the one or more additions.
Yet another and/or alternative non-limiting objective of the present invention is the provision of producing a magnesium composite that includes one or more additives that have a solubility in the molten magnesium or magnesium alloy of less than about 10%.
The mechanical properties such as tensile strength and yield strength of magnesium alloy are improved by adding gadolinium and yttrium to the magnesium alloy. Tensile strength is the resistance of a material to breakage under tension and it is usually obtained by the stress-strain curve. The unit is usually in MPa or KSl etc. Elongation is the amount of extension of an object under stress upon breakage, usually expressed as a percentage of the original length. In the application in oil and gas industries, such as frac balls, frac plugs or frac seats, not only has the magnesium alloys to be dissolved in a medium, but also the alloys need to have higher mechanical strength to withstand the high pressure and high temperature scenario.
It is desirable to alloy iron, copper, and nickel to the baseline to accelerate corrosion. Nickel, copper, iron, or a combination of the three may be added to achieve a specific dissolution rate by intra-granular or intergranular galvanic corrosion. Copper alone will not have a sufficient corrosion rate for many conditions. Nickel and iron may drop out of solution if an improper amount is added. Tuning the corrosion rate without a detrimental impact to mechanical properties often requires a combination of two elements in a particular amount.
The present invention is directed to a novel magnesium composite that can be used to form a castable, moldable, or extrudable component. The magnesium composite includes at least 50 wt. % magnesium. Generally, the magnesium composite includes over 50 wt. % magnesium and less than about 99.5 wt. % magnesium and all values and ranges therebetween. One or more additives are added to a magnesium or magnesium alloy to form the novel magnesium composite of the present invention. The one or more additives can be selected and used in quantities so that galvanically-active intermetallic or insoluble precipitates form in the magnesium or magnesium alloy while the magnesium or magnesium alloy is in a molten state and/or during the cooling of the melt; however, this is not required. The one or more additives are added to the molten magnesium or magnesium alloy at a temperature that is typically less than the melting point of the one or more additives; however, this is not required. During the process of mixing the one or more additives in the molten magnesium or magnesium alloy, the one or more additives are not caused to fully melt in the molten magnesium or magnesium alloy; however, this is not required. For additives that partially or fully melt in the molten magnesium or molten magnesium alloy, these additives form alloys with magnesium and/or other additives in the melt, thereby resulting in the precipitation of such formed alloys during the cooling of the molten magnesium or molten magnesium alloy to form the galvanically-active phases in the magnesium composite. After the mixing process is completed, the molten magnesium or magnesium alloy and the one or more additives that are mixed in the molten magnesium or magnesium alloy are cooled to form a solid magnesium component that includes particles in the magnesium composite. Such a formation of particles in the melt is called in situ particle formation. Such a process can be used to achieve a specific galvanic corrosion rate in the entire magnesium composite and/or along the grain boundaries of the magnesium composite. This feature results in the ability to control where the galvanically-active phases are located in the final casting, as well as the surface area ratio of the in situ phase to the matrix phase, which enables the use of lower cathode phase loadings as compared to a powder metallurgical or alloyed composite to achieve the same dissolution rates. The in situ formed galvanic additives can be used to enhance mechanical properties of the magnesium composite such as ductility, tensile strength, and/or shear strength. The final magnesium composite can also be enhanced by heat treatment as well as deformation processing (such as extrusion, forging, or rolling) to further improve the strength of the final composite over the as-cast material; however, this is not required. The deformation processing can be used to achieve strengthening of the magnesium composite by reducing the grain size of the magnesium composite. Further enhancements, such as traditional alloy heat treatments (such as solutionizing, aging and/or cold working) can be used to enable control of dissolution rates through precipitation of more or less galvanically-active phases within the alloy microstructure while improving mechanical properties; however, this is not required. Because galvanic corrosion is driven by both the electrode potential between the anode and cathode phase, as well as the exposed surface area of the two phases, the rate of corrosion can also be controlled through adjustment of the in situ formed particles size, while not increasing or decreasing the volume or weight fraction of the addition, and/or by changing the volume/weight fraction without changing the particle size. Achievement of in situ particle size control can be achieved by mechanical agitation of the melt, ultrasonic processing of the melt, controlling cooling rates, and/or by performing heat treatments. In situ particle size can also or alternatively be modified by secondary processing such as rolling, forging, extrusion and/or other deformation techniques. A smaller particle size can be used to increase the dissolution rate of the magnesium composite. An increase in the weight percent of the in situ formed particles or phases in the magnesium composite can also or alternatively be used to increase the dissolution rate of the magnesium composite.
In accordance with the present invention, a novel magnesium composite is produced by casting a magnesium metal or magnesium alloy with at least one component to form a galvanically-active phase with another component in the chemistry that forms a discrete phase that is insoluble at the use temperature of the dissolvable component. The in situ formed particles and phases have a different galvanic potential from the remaining magnesium metal or magnesium alloy. The in situ formed particles or phases are uniformly dispersed through the matrix metal or metal alloy using techniques such as thixomolding, stir casting, mechanical agitation, chemical agitation, electrowetting, ultrasonic dispersion, and/or combinations of these methods. Due to the particles being formed in situ to the melt, such particles generally have excellent wetting to the matrix phase and can be found at grain boundaries or as continuous dendritic phases throughout the component depending on alloy composition and the phase diagram. Because the alloys form galvanic intermetallic particles where the intermetallic phase is insoluble to the matrix at use temperatures, once the material is below the solidus temperature, no further dispersing or size control is necessary in the component. This feature also allows for further grain refinement of the final alloy through traditional deformation processing to increase tensile strength, elongation to failure, and other properties in the alloy system that are not achievable without the use of insoluble particle additions. Because the ratio of in situ formed phases in the material is generally constant and the grain boundary to grain surface area is typically consistent even after deformation processing and heat treatment of the composite, the corrosion rate of such composites remains very similar after mechanical processing.
The present invention disclosure shows the dissolvable magnesium alloy compatible for the conditions associated with downhole operations, such as hydraulic fracturing operations. When the dissolvable magnesium alloy is formed in a component of a downhole tool, the component must have the same functionality as the conventional non-dissolving component. The component must be sufficiently strong to hold a pressure differential around 7.5 ksi as assembled in the downhole tool. There may be other components of the dissolvable magnesium alloy in the downhole tool as well. The component must also dissolve in a wellbore fluid, such as a potassium chloride brine, after the downhole operation is completed. The alloy remains strong, and ductile to be formed into a component and functional as a downhole tool. The dissolvability is controlled within a range for a potassium chloride brine. Additionally, the yield strength, ultimate tensile strength, and elongation of the present invention are sufficient to function as component of a downhole tool, despite the additives in grains of the magnesium to affect overall strength.
In one embodiment, gadolinium and yttrium in magnesium alloys are used to improve the mechanical properties (tensile strength and yield strength) of magnesium alloys. Elements of copper, nickel, gallium and indium are used to improve the solubility of various other metal elements. Moreover, copper, nickel, gallium, indium and silicon in magnesium alloys increase the reaction rate of magnesium alloys with a medium. Other elements in magnesium alloys, such as aluminum, zinc, zirconium, rhenium, iron, beryllium and calcium, may serve to catalyze the improvement of the mechanical properties of magnesium alloys.
As shown in FIG. 1 , AZ31 is used to compare to Alloys 1, 2, 3, 4, 5 and 6. In another word, AZ31 may be considered a baseline for magnesium alloy development. The alloy is 3 weight % aluminum, 1 weight % zinc, with the balance of magnesium. A yield of 30 ksi and UTS of 38 ksi are paired with an elongation of 15%.
The FIG. 1 demonstrates the low and high mechanical properties boundaries of aluminum content manipulation. First, by starting with a baseline alloy of Mg (alloy 1), 0.5% wt Al, 1.4% wt Cu, and 0.15% wt Ni, a yield of 18.2 ksi was achieved with an elongation of 8.1%. The elongation would be sufficient for a component of a downhole tool, but the yield strength may be lacking. To test the upper bounds of aluminum content, as shown in Table 1, Alloy 2 was created with 10% wt Al, 1.4% wt Cu, 1% wt Zn and 0.15% wt Ni, achieving a yield of 29.2 ksi and a ductility of 12.8%. The resultant alloy mirrors the strength of AZ31, but lacks the ductility. Then, setting the aluminum content at roughly half of Alloy 2, and unexpected result was measured in Alloy 3 in that the ductility exceeded both alloys by 50% with mechanical strength in line with the stronger alloy. A chemistry of 5.6% wt Al, 1.4% wt Cu, and 0.15% wt Ni achieved these surprising results.

TABLE 1

Composition of various alloys

Alloy	Composition

Alloy
1	0.5% wt Al, 1.4% wt Cu, 0.15% wt Ni, and the balance of Mg
	(97.95 wt %)
Alloy 2	10% wt Al, 1.4% wt Cu, 1% wt Zn, 0.15% wt Ni, and the
	balance of Mg (87.45%)
Alloy 3	5.6% wt Al, 1.4% wt Cu, and 0.15% wt Ni, and the balance of
	Mg (92.85%)
Alloy 4	0.5% wt Al, 1.4% wt Cu, 0.15% wt Ni, and the balance of Mg
	(97.95%)
Alloy 5	3.1% wt Gd, 1.4% wt Cu, 0.15% wt Ni, and the balance of Mg
	(95.35%)
Alloy 6	3.1% wt Gd, 1.4% wt Cu, 0.15% wt Ni, 4% wt Y, and the
	balance of Mg (91.35%)
Alloy 7	3.3% wt Al, 1% wt Gd, 0.6% wt Y, 11% wt Li, 0.4% wt Ni,
	0.2% wt Cu, and the balance of Mg (83.5%)

The yield and UTS of Alloy 3 fits in the window close to AZ31, but the ductility unexpected exceeded the base and modified chemistries. Then, again improving on Alloy 1, Alloy 4 was created by adding 3.1 wt % gadolinium with 0.5 wt % Al, 1.4 wt % Cu, and 0.15 wt % Ni, achieving a remarkable increase in the yield strength to 37 ksi, a 100% increase, with ductility staying constant. Alloy 4 sees an unexpected increase in mechanical properties compared to alloy 1 after an addition of gadolinium.
Alloy 5 was created by removing the aluminum from alloy 4, with a formulation of 3.1 wt % Gd, 1.4 wt % Cu, and 0.15 wt % Ni having the startling effect of a dramatic increase in ductility to 16%, a 50% improvement over Alloy 4. The yield strength fell relative to alloy 4 to 23.8 ksi. The ductility for alloy 5 unexpectedly is increased while the yield and UTS is essentially unchanged from alloy 1 after the removal of aluminum and addition of gadolinium equal to alloy 4. Alloy 6 results in the increase of all properties with the addition of yttrium to alloy 5.
More specifically, alloy 6 improves upon Alloy 5 with the addition of 4 wt % Y, with 3.1 wt % Gd, 1.4 wt % Cu, and 0.15 wt % Ni. Again, the yield strength experienced a dramatic increase to 32.4 ksi, a 40% increase, while increasing the ductility to 17.5%. Yttrium unexpectedly optimized both mechanical strength and ductility in alloy 6.
FIG. 2 illustrates the measured room temperature longitudinal mechanical properties of alloy 1 through 6, demonstrating the variety of useful mechanical properties required in different downhole components. More specifically, FIG. 2 shows values of the yield strength, ultimate tensile strength, and elongation for the material at room temperature from specimens oriented in the longitudinal direction. These are further enumerated in Table 2 with the transverse mechanical properties at room temperature.

TABLE 2

Tabulated values of the yield strength, ultimate tensile strength,
and elongation for the material at room temperature from specimens
oriented in the longitudinal and transverse directions.

Longitudinal

Transverse

	Long.	Long.	Long.	Trans.	Trans.	Trans.
	Yield	UTS	Elong.	Yield	UTS	Elong.
Alloy	(ksi)	(ksi)	(%)	(ksi)	(ksi)	(%)

AZ31	29.0	37.0	15.0
Alloy 1	18.2	29.2	8.1	7.7	22.6	11.0
Alloy 2	29.2	42.1	12.8	17.4	28.2	3.9
Alloy 3	24.4	38.7	17.0	12.4	33.7	13.2
Alloy 4	37.0	40.0	8.0	33.1	38.5	8.1
Alloy 5	23.8	32.7	16.0	20.3	31.3	19.9
Alloy 6	32.4	46.6	17.5	22.6	37.6	14.0
Alloy 7	16.6	20.3	38.0

FIG. 3 shows the unexpected thermally stable mechanical properties of alloy 6. More specifically, FIG. 3 demonstrate the mechanical properties of alloy 6 as a function of temperature at 23, 95, 125, 150, and 175° C. Generally, the mechanical properties are stable from 23 to 175° C. Standard magnesium alloys experience a dramatic decrease in strength with an increase in temperature. It is a noteworthy result that there is less than a 10% decline in yield strength when measured from 23° C. to 175° C.
FIG. 4 contrasts the relative yield strength stability of alloy 6 to the alloys 1 through 5. Indeed, FIG. 4 shows a plot of the normalized yield strength at 23, 95, 125, 150, and 175° C. for alloys 1 through 6. Unlike alloy 6, most alloys including alloys 1-5 experience a significant decline in mechanical properties, even those with an equal amount of gadolinium. Yttrium unexpectedly acts as a thermal stabilizer for mechanical properties when gadolinium on its own was expected to. Because alloys 1 through 3 are lacking rare earth metals, they experience dramatic declines in yield strength. Alloys 4 and 5 demonstrate the typical moderate decrease in yield strength seen in magnesium-rare earth alloys, while alloy 6 only experiences a minimal decrease.
A unique feature of Alloy 6 is that it does not experience stress corrosion cracking unlike other commercial alloys. In a separate test, alloy 6 has been tested together with two commercial available alloys having rare earth. The two commercial available alloys experienced a dramatic loss in ductility when tested in conducted in 140° C. tap water at a rate of 4.00×10⁻⁶in/in/s. Alloy 6 solves the problem of rapid cracking in these alloys with only a moderate loss in ductility.
In another embodiment, alloy 7 is made with 3.3 wt % Al, 1 wt % Gd, 0.6 wt % Y, 11 wt % Li, 0.4 wt % Ni, and 0.2 wt % Cu. The lithium addition is to increase the ductility, as one skilled in the art would know. Unexpectedly, the ductility increased more than what a skilled practitioner would expect. FIG. 5 shows mechanical properties for the alloy 7 as a function of temperature, such as at 23, 95, 125, 150, and 175° C. The 36% ductility at room temperature increases to 60% at 95° C., a common frac plug utilization temperature. No other magnesium alloy can achieve this result.
FIG. 6 compares the room temperature ductility of alloy 7 to the others in this disclosure. Alloy 7 has shown a ductility of at least 100% more than any other alloy.
FIG. 7 compares the unique compressive properties of alloy 7 (right side) to two other high ductility materials, alloy 5 (left) and 6 (center), at 23° C. These display the standard 45° fracture face with little net geometry change. Alloy 7 showed high plasticity in that it is compressed to an unexpected 50% of original height with no cracking, a result that has not been seen in any other magnesium alloys.
FIG. 8 depicts the as-cast dissolution rate for the seven alloys compared to AZ31. A skilled practitioner recognizes that adding copper and nickel to magnesium may increase the dissolution rate, while rare earth and aluminum may decrease the corrosion rate. The nickel and copper content was essentially constant across the 7 materials. FIG. 8 shows the change in extruded dissolution rate by adding nickel, copper, aluminum, gadolinium in various combinations. By removing zinc and most aluminum, then adding nickel and copper from AZ31, alloy 1 was discovered to have a high dissolution rate. Increasing the aluminum to 10 wt % and adding 1 wt % zinc resulted in a lower dissolution rate for alloy 2. Alloy 3 was found to have a moderate corrosion rate due to the precipitation of the Q phase. The addition of 3.1 wt % Gd to alloy 1 resulted in an increase in the corrosion rate of the resulting alloy 4. Literature states that the addition of rare earth decreases the corrosion rate of the resultant magnesium alloy. It unexpectedly appears the combination of a small amount of aluminum, nickel, and/or copper with rare earth actually increases the corrosion rate. Aluminum is removed from alloy 4, dramatically decreasing the corrosion rate of alloy 5. Based on the results of alloy 4, it was unforeseen to have such a dramatic drop. A lower dissolution rate material is useful for high surface area components. Alloy 6 becomes more reactive when yttrium is added to alloy 5, an unexpected result. Lithium being added to alloy 4 results in a decrease in dissolution rate for Alloy 7. Surprisingly, alloy 3 has a lower dissolution rate than alloy 2, which has more aluminum. Further, alloy 4 has the unexpected result of an increased corrosion rate with the addition of rare earth. Even more astonishing was that the removal of aluminum from alloy 4 to create alloy 5 led to a dramatic drop in corrosion rate, where the skilled practitioner would anticipate a moderate increase. The addition of yttrium to alloy 5 to create alloy 6 led to another unexpected result of an increase in corrosion rate, where rare earth alloys are supposed to enhance corrosion resistance.
Still in FIG. 8 , an alloy 2 testing the upper bounds of aluminum content with the composition of 10 wt % aluminum, 1 wt % zinc, 1.5 wt % copper, and 0.1 wt % nickel is created. The alloy 2 has a yield of 29 ksi, UTS of 42 ksi, and an elongation of 13%. The mechanical properties are very similar to AZ31, but with a higher dissolution rate. A standard AZ31 alloy has Al₁₂Mg₁₇form as a second phase, which forms in this case as seen in FIG. 9 c . Within the range of 0.5 to 10 wt % aluminum, there is no improvement over the baseline AZ31 material other than desired increased dissolution rate (57 mg/cm²/hr in 2.1 weight % KCl) due to the copper and nickel. The unique combination of copper and nickel formed 2% Q-phase (Al₇Cu₃Mg₆) which resulted in a moderate corrosion rate.
The strength of an alloy is contingent upon the ease with which dislocations move. Opposing dislocation motion increases mechanical strength. The addition of rare earth acts as a grain refiner in magnesium, as smaller grains hinder dislocation motion. Dislocations may be pinned due to stress field interactions with other dislocations and solute particles, creating physical barriers from second phase precipitates forming along grain boundaries. Further, rare earth depresses the corrosion rate. It is expected that corrosion will decrease significantly; the elongation would be similar, with a modest increase in yield and UTS.
The addition of 3.1 wt % gadolinium to 1.4 wt % copper, 0.6 wt % aluminum, and 0.15 wt % nickel (alloy 4) results in the formation of LPSO structures, specifically 14H. A yield strength of 37 ksi and UTS of 40 ksi is achieved with an elongation of 9%. Two important deviations from expectations occur. First, the yield doubled and secondly, the corrosion rate stays high (55 mg/cm²/hr in 2.1 weight % KCl). A modest increase in the UTS (40 ksi) of 33% is observed.
The combination of aluminum and gadolinium are known to act as a corrosion inhibitor. However, in this alloy, the corrosion rate increased from 45 to 55 mg/cm²/hr compared to embodiment without gadolinium.
Increasing the aluminum content and adding zinc (alloy 2) results in a dissolution rate of 57 mg/cm²/hr. Removing zinc and lowering aluminum to 5.6 weight % (Alloy 3) results in a dissolution rate of 45 mg/cm²/hr. Then, by adding 3.1 gadolinium, a dissolution rate of 55 mg/cm²/hr is measured in 2.1% KCl at 95° C. By removing aluminum, a dissolution rate of 13 mg/cm²/hr is measured in 2.1% KCl at 95° C. FIG. 3 demonstrates that copper and nickel clearly work as a corrosion accelerant, as will aluminum. In this particular set of alloys, gadolinium acts as both a corrosion inhibitor and accelerant.
In a final embodiment, aluminum is removed and 0.4 weight % zirconium is added with the expectation of a lower yield and UTS due to fewer phases generated, a modest increases in ductility, and a moderate decrease in dissolution rate. As expected, the yield decreased to 24 ksi, with UTS decreasing to 33 ksi. Surprisingly, the elongation is more than doubled to 19%, very similar to the 5.6 wt % Al alloy. No similar phases are formed between these two alloys, as seen in FIG. 9 e . However, a LPSO phase formed as verified from XRD, which instead results in a high elongation. Most unexpectedly, the dissolution rate dropped dramatically from 55 to 13 mg/cm²/hr in 2.1 weight % KCl. The phase are most similar to the Mg-1.4Cu-0.6Al-0.15Ni alloy with Mg₂Cu and Mg₂Ni, which had a very high dissolution rate.
FIG. 9 shows the scanning electron microscopy (SEM) images of the alloys, with an energy dispersive X-ray spectroscopy (EDS) overlay to show where elements concentrate for potential phase identification. As shown in FIG. 9 a , alloy 1 is at 1500× magnification via SEM on left and EDS at 3500× on right identifies several phases that accelerate corrosion. Mg₂Cu is observed in locations 1, 3, and 4. Mg₂Ni is found in locations 2 and 7. A complex phase of Ni, Cu, and Al is found in locations 5-6. No feature is observed in the microstructure that will contribute to higher mechanical properties than a base AZ31.
As shown in FIG. 9 b , alloy 2 is at 350× magnification via SEM on left. EDS at 3500× identifies Mg₁₇Al₁₂in large quantities creating semi-enclosed cells that will reduce the rate of corrosion and increase the mechanical strength. Al₇Cu₃Mg₆is formed which likely contributed to the higher corrosion rate. An AlMgZn tau phase is formed roughly double in proportion to the Al₇Cu₃Mg₆phase. These secondary phases contribute to the increase in the mechanical properties. These formed rather than the Laves phases (Mg₂X) seen in alloy 1.
FIG. 9 c shows alloy 3 at 350× magnification via SEM on left. EDS at 3500× identifies Mg₁₇Al₁₂in moderate quantities creating poorly-enclosed cells that will minimally delay corrosion while enhancing mechanical properties. The unique microstructure provides moderate mechanical strength with numerous second phases to pin dislocations, thus increasing the ductility. Location 1 shows where an AlNi phase precipitates, which will also increase corrosion rate. Location 2 is an instance of Al₇Cu₃Mg₆phase, which contributes to the resultant mechanical properties.
Alloy 1 has fewer secondary phases than alloy 2. Alloy 3 had fewer secondary phases than Alloy 2, but a higher ductility. Alloy 5 has more secondary phases than alloy 3, with slightly lower ductility. The cuboidal features in the alloys formed from the copper and nickel addition act to increase the corrosion rate.
FIG. 9 d shows alloy 4 at 500× magnification via SEM on left, EDS at 5000× on right. FIG. 9 e shows alloy 5 at 350× magnification via SEM on left. EDS at 3500× identifies the locations of the LPSO phases at 1, 2, and 3. These are formed without the inclusion of zinc in the alloy, contrary to much of literature. Locations 4 and 5 show instances of the Mg₂Cu phase which contribute to accelerated corrosion.
FIG. 9 f shows alloy 6 at 350× magnification via SEM on left and EDS at 1500× on the right. FIG. 9 g illustrates Alloy 7 at 350× magnification via SEM on left. And EDS at 1500× on the right.
FIG. 10 shows an optical image of alloy 1, alloy 4, and alloy 5 at 100× and demonstrates the microstructure evolution from the alloying process. Taking alloy 1 as a baseline, adding Gd to create alloy 4 results in the formation of secondary phases which lend themselves to enhancing the mechanical properties. Removing the aluminum from alloy 1 while adding gadolinium results in alloy 5, with a new set of phases giving the high ductility measured in mechanical testing.
FIGS. 11 a-c show optical microstructures of alloy 1 (left), alloy 6 (center), and alloy with an extra yttrium (right) at 500× and demonstrates a boundary case of too much yttrium. Using Alloy 1 as a baseline, Alloy 6 is created with the addition of yttrium and gadolinium. Alloy 6 forms a network of semi-interconnected secondary phases with the addition of gadolinium and yttrium. Right (FIG. 11 c ) results from an increase in yttrium relative to gadolinium. Too much yttrium resulted in poor processing and properties. The semi-interconnected secondary phases lend themselves to high, thermally stable mechanical properties. Holding all other elements constant, the introduction of more yttrium created a large volume percentage of secondary phases, resulting in a strong but brittle alloy that had few uses in frac plugs.
FIGS. 12 a-d show the binary phase diagrams of magnesium and several alloying elements that a skilled practitioner would reference to anticipate solubility. More specifically, FIG. 12 a discloses binary phase diagram of magnesium and aluminum. As expected from this diagram, most but not all aluminum containing magnesium alloys formed the Mg₁₇Al₁₂phase. A magnesium alloy with an aluminum content roughly between the maximum and minimum is created with the composition of 5.6 wt % aluminum, 0.4 wt % copper, and 1.4 wt % nickel (Alloy 3). Unexpectedly, both the longitudinal (21%) and transverse (13%) elongations increased to values higher than baseline AZ31 alloy. It is not inherent that aluminum will increase the elongation; one skilled in the art expects increasing aluminum content to decrease the ductility. For example, AZ91 has nominally 9 wt % aluminum with a ductility of 3-7%. The unique result is not expected by one skilled in the art. FIG. 9 c shows the open cells with small grains from which the high ductility emerges. From FIG. 12 a , there is no phase change from 5.6 to 10 wt % aluminum in a binary magnesium-aluminum phase diagram. Also, the yield is 25 ksi, with a high UTS (39 ksi). Typically, a magnesium alloy will have a high elongation or UTS, not both. A standard AZ31 alloy has Al₁₂Mg₁₇form as a second phase, which also exists. The unique combination of copper and nickel formed 1% Q-phase (Al₇Cu₃Mg₆) which resulted in a moderate corrosion rate (45 mg/cm²/hr in 2.1 weight % KCl). Unexpectedly, no unique phase exists in this alloy compared to the former two cases that explain the high elongation.
FIG. 12 b teaches binary phase diagram of magnesium and zinc. The predicted zinc phase at low concentrations never materialize due to the alloying in alloy 2. Alloys other than alloys 3 through 5 may benefit from zinc addition based on the results from alloy 1 to 2. FIG. 12 c reveals binary phase diagram of magnesium and nickel. The predicted nickel phase at low concentrations precipitated in most cases, but also formed more complex phases that the skilled practitioner would not anticipate, leading to novel results. FIG. 12 d discloses binary phase diagram of magnesium and copper. The predicted copper phase at low concentrations precipitates in most cases, but also forms more complex phases that the skilled practitioner would not anticipate, leading to novel results.
FIG. 13 displays the X-Ray Diffraction (XRD) measurement of phases for the Mg-3Gd-1.4Cu in alloy 5 showing the creation of beneficial secondary phases. For example, the long-period stacking-order (LPSO 14H) structure will result in high strength and moderate ductility. To form LPSO phases, the rare earth elements must have negative mixing enthalpy not only with Mg, the hexagonal close-packed structure at room temperature, a large solid-solubility (>3.75 at. %) in Mg and an atomic size larger than Mg by 8%.
FIG. 14 displays the X-Ray Diffraction (XRD) measurement of phases for the Mg-3Gd-4Y-1.4Cu in alloy 6 showing the creation of beneficial secondary phases. For example, the long-period stacking-order structure will result in high strength and moderate ductility. To form LPSO phases, the rare earth elements must have negative mixing enthalpy not only with Mg, the hexagonal close-packed structure at room temperature, a large solid-solubility (>3.75 at. %) in Mg and an atomic size larger than Mg by 8%.
FIG. 15 shows the CALPHAD simulation for the Mg-3Gd-4Y-1.4Cu in alloy 6 with the mole fraction of phases formed during casting. Starting with a high temperature, the simulation predicts what elements/phases appear with dropping temperature. XRD work confirmed the presence of many of these alloys.
FIG. 16 shows alloy 4 and alloy 4 modification using the same weight percentage rare earth neodymium instead of gadolinium. It demonstrates that the claimed mechanical performances can be materially replicated by substituting in one rare earth for another. In this instance, alloy 4 is compared to a modified version with an identical chemistry except the gadolinium is removed and replaced with an equal amount of neodymium, for example.
All known dissolvable magnesium alloys start from a chemistry in the range of 0-20 wt % lithium, 0-15 wt % gadolinium, 0-15 wt % yttrium, 0-2 wt % copper, 0-2 wt % nickel, 0-2 wt % zirconium, 0-15 wt % aluminum, and up to 10% total of other elements including but not limited to manganese, neodymium, cerium, calcium, iron, bismuth, indium, and silver with the balance magnesium. With all zero, plain elemental magnesium is the starting point.
From the testing Mg-3Gd-4Y-1.4Cu in alloy 6 is at least one embodiment of the dissolvable magnesium alloy of the present invention. The strength (tensile yield strength, ultimate tensile strength) and performance (elongation and dissolution rate) are compatible with components of a downhole tool. More specifically, one chemistry of Mg-3Gd-4Y-1.4Cu alloy has the form of 3.1 wt % gadolinium, 4 wt % yttrium, 1.4 wt % copper, 0.15 wt % nickel, and 0.4 wt % zirconium with magnesium as the balance. This embodiment of the present invention achieves 32.4 ksi yield, 46.6 ksi UTS, 17.5% elongation, and a dissolution rate of 25 mg/cm²/hr in 95° C. 2.1 wt % KCl. Removing the copper and nickel from this chemistry may also form a corrosion resistant alloy for long duration applications.

EXAMPLE 1

In one embodiment, magnesium alloy of the present invention comprises 0.5% wt Al, 1.4% wt Cu, 0.15% wt Ni, 97.95 wt % Mg. In one embodiment, the production process is as follows:
Weighing raw materials such as magnesium, aluminum, copper, nickel, and pretreating magnesium, aluminum, copper, and nickel at 100 C for 5 h; mixing the raw materials, and then smelting them in a crucible electric resistance furnace, covering them with a covering agent, and refining them with a refining agent, thus the components are uniformly mixed, removing the inclusions, and casting the materials at 670 C to form an ingot; subjecting the ingot to a homogenization heat treatment at 450 C for a treatment time of 8 h; subjecting the ingot to a forging processing at 350 C so as to obtain a forged piece; subjecting the forged piece to an aging heat treatment at room temperature for a treatment time of 20 h.
More specifically, commercially pure magnesium was melted to above 660° C. and at least 200° C. below the boiling point of magnesium at 1090° C. About 0.04 wt. % of nickel, 0.6 wt % of Al, 0.4 wt % Cu was added to the melt and dispersed. The melt was cast into a steel mold. It was cooled down to room temperature. The cast billet was extruded between 350-380° C. at 0.7 mm/s. The extruded material exhibited a yield strength of 18.2 ksi, tensile strength of about 37 ksi, an elongation of about 15%. The material dissolved at a rate of about 61.6 mg/cm²-hr in a 0.21% KCl solution at 95° C. The material dissolved at a rate of 87.8 mg/cm²-hr in a 1.05% KCl solution at 95° C. The material dissolved at a rate of 90.9 mg/cm²-hr. in a 2.1% KCl solution at 95° C.
Alloy 2: Commercially pure magnesium was melted to above 660° C. and at least 200° C. below the boiling point of magnesium at 1090° C. About 0.18 wt. % of nickel, 9.7 wt % of Al, 1.47 wt % Cu, 0.16 wt % Mn, 0.45 wt % Zn was added to the melt and dispersed. The melt was cast into a steel mold. It was cooled down to room temperature. The cast billet was extruded between 350-380° C. at 0.6 mm/s. The extruded material exhibited a yield strength of 29.2 ksi, tensile strength of about 42.1 ksi, an elongation of about 12.8%. The material dissolved at a rate of about 35.8 mg/cm²-hr in a 0.21% KCl solution at 95° C. The material dissolved at a rate of 55.3 mg/cm²-hr in a 1.05% KCl solution at 95° C. The material dissolved at a rate of 57.2 mg/cm²-hr. in a 2.1% KCl solution at 95° C.
Alloy 3: Commercially pure magnesium was melted to above 660° C. and at least 200° C. below the boiling point of magnesium at 1090° C. About 1.4 wt. % of nickel, 5.6 wt % of Al, 0.4 wt % Cu, 0.02 wt % Si, was added to the melt and dispersed. The melt was cast into a steel mold. It was cooled down to room temperature. The cast billet was extruded between 350-380° C. at 7 mm/s. The extruded material exhibited a yield strength of 24.4 ksi, tensile strength of about 38.7 ksi, an elongation of about 17%. The material dissolved at a rate of about 25.3 mg/cm²-hr in a 0.21% KCl solution at 95° C. The material dissolved at a rate of 37 mg/cm²-hr in a 1.05% KCl solution at 95° C. The material dissolved at a rate of 45.8 mg/cm²-hr. in a 2.1% KCl solution at 95° C.
Alloy 4: Commercially pure magnesium was melted to above 660° C. and at least 200° C. below the boiling point of magnesium at 1090° C. About 0.04 wt. % of nickel, 0.4 wt % of Zr, 0.4 wt % Cu, 3.1 wt % Gd, was added to the melt and dispersed. The melt was cast into a steel mold. It was cooled down to room temperature. The cast billet was extruded between 350-380° C. at 0.7 mm/s. The extruded material exhibited a yield strength of 37 ksi, tensile strength of about 40 ksi, an elongation of about 8%. The material dissolved at a rate of about 32 mg/cm²-hr in a 0.21% KCl solution at 95° C. The material dissolved at a rate of 52 mg/cm²-hr in a 1.05% KCl solution at 95° C. The material dissolved at a rate of 54 mg/cm²-hr. in a 2.1% KCl solution at 95° C.
Alloy 5: Commercially pure magnesium was melted to above 660° C. and at least 200° C. below the boiling point of magnesium at 1090° C. About 0.04 wt. % of nickel, 0.6 wt % of Al, 0.4 wt % Cu, was added to the melt and dispersed. The melt was cast into a steel mold. It was cooled down to room temperature. The cast billet was extruded between 390-440° C. at 0.6 mm/s. The extruded material exhibited a yield strength of 23.8 ksi, tensile strength of about 32.7 ksi, an elongation of about 16%. The material dissolved at a rate of about 5.2 mg/cm²-hr in a 0.21% KCl solution at 95° C. The material dissolved at a rate of 7.1 mg/cm²-hr in a 1.05% KCl solution at 95° C. The material dissolved at a rate of 13.1 mg/cm²-hr. in a 2.1% KCl solution at 95° C.
Alloy 6: Commercially pure magnesium was melted to above 660° C. and at least 200° C. below the boiling point of magnesium at 1090° C. About 0.15 wt. % of nickel, 0.4 wt % of Zr, 1.4 wt % Cu, 3.1 wt % Gd, 4 wt % Y was added to the melt and dispersed. The melt was cast into a steel mold. It was cooled down to room temperature. The cast billet was extruded between 390-440° C. at 0.6 mm/s. The extruded material exhibited a yield strength of 32.4 ksi, tensile strength of about 46.6 ksi, an elongation of about 17.5%. The material dissolved at a rate of about 35.8 mg/cm²-hr in a 0.21% KCl solution at 95° C. The material dissolved at a rate of 55.3 mg/cm²-hr in a 1.05% KCl solution at 95° C. The material dissolved at a rate of 57.2 mg/cm²-hr. in a 2.1% KCl solution at 95° C.
Alloy 7: Commercially pure magnesium was melted to above 660° C. and at least 200° C. below the boiling point of magnesium at 1090° C. About 0.04 wt. % of nickel, 0.6 wt % of Al, 0.4 wt % Cu, 3.1 wt % Gd, 14 wt %. Li was added to the melt and dispersed. The melt was cast into a steel mold. It was cooled down to room temperature. The cast billet was extruded between 350-380° C. at 0.7 mm/s. The extruded material exhibited a yield strength of 16.9 ksi, tensile strength of about 20.3 ksi, an elongation of about 52.2%. The material dissolved at a rate of about 9 mg/cm²-hr in a 0.21% KCl solution at 95° C. The material dissolved at a rate of 29 mg/cm²-hr in a 1.05% KCl solution at 95° C. The material dissolved at a rate of 46 mg/cm²-hr. in a 2.1% KCl solution at 95° C.
The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated structures, construction and method can be made without departing from the true spirit of the invention.

Claims

We claim:

1. A dissolvable magnesium composite that at least partially forms a ball, a frac ball, a tube, a plug or other tool component that is to be used in a well drilling or completion operation, said dissolvable magnesium composite includes in situ precipitate, said dissolvable magnesium composite comprising a mixture of magnesium or a magnesium alloy and an additive material, said magnesium composite includes greater than about 60 wt. % magnesium, said in situ precipitate includes said additive material, said additive material includes one or more metal materials selected from the group consisting of:

a) nickel, wherein said nickel constitutes about 0.04-0.4 wt. % of said dissolvable magnesium composite, and

b) copper, wherein said copper constitutes about 0.1-10 wt. % of said dissolvable magnesium composite,

said dissolvable magnesium composite has a dissolution rate of at least 10 mg/cm²/hr. in 2.1 wt. % KCl water mixture at 93° C.

2. The dissolvable alloy of claim 1, wherein said dissolvable magnesium composite has yield strength in a range of from about 25 to about 37 ksi.

3. The dissolvable alloy of claim 1, wherein said dissolvable magnesium composite has ultimate tensile strength in a range of from about 35 to about 45 ksi.

4. The dissolvable alloy of claim 1, wherein said dissolvable magnesium composite has an elongation in a range of from about 10 to about 19%.

5. The dissolvable alloy of claim 1, wherein said magnesium alloy comprises greater than 60 wt. % magnesium and no more than 10 wt. % aluminum, and one or more metals selected from the group consisting of 0.5-10 wt. % aluminum, 0.1-2 wt. % zinc, and 0.15-2 wt. % manganese.

6. The dissolvable alloy of claim 1, wherein said magnesium alloy comprises greater than 60 wt. % magnesium and no more than 10 wt. % aluminum, and one or more metals selected from the group consisting of 0.5-10 wt. % gadolinium, 0.1-6 wt. % yttrium, and 0.15-12 wt. % lithium.

7. The dissolvable alloy of claim 1, wherein said additive material includes nickel, said nickel constitutes 0.15-0.4 wt. % of said dissolvable magnesium composite.

8. A dissolvable magnesium cast composite comprising a mixture of magnesium or a magnesium alloy and an additive material, said additive material includes one or more metals selected from the group consisting of a) copper wherein said copper constitutes at least 0.01 wt. % of said dissolvable magnesium cast composite, and b) nickel wherein said nickel constitutes at least 0.01 wt. % of said dissolvable magnesium cast composite, said magnesium composite includes in situ precipitate, said in situ precipitate includes said additive material, a plurality of particles of said in situ precipitate having a size of no more than 50 μm, said magnesium composite has a dissolution rate of at least 5 mg/cm²/hr. in 3 wt. % KCl water mixture at 90° C.

9. The dissolvable alloy of claim 8, wherein said dissolvable magnesium composite has yield strength in a range of from about 25 to about 37 ksi.

10. The dissolvable alloy of claim 8, wherein said dissolvable magnesium composite has ultimate tensile strength in a range of from about 35 to about 45 ksi.

11. The dissolvable alloy of claim 8, wherein said dissolvable magnesium composite has an elongation in a range of from about 10 to about 19%.

12. The dissolvable alloy of claim 8, wherein said magnesium alloy comprises greater than 50 wt. % magnesium and no more than 10 wt. % aluminum, and one or more metals selected from the group consisting of 0.5-10 wt. % aluminum, 0.1-2 wt. % zinc, and 0.15-2 wt. % manganese.

13. The dissolvable alloy of claim 8, wherein said magnesium alloy comprises greater than 60 wt. % magnesium and no more than 10 wt. % aluminum, and one or more metals selected from the group consisting of 0.5-10 wt. % gadolinium, 0.1-6 wt. % yttrium, and 0.15-12 wt. % lithium.

14. The dissolvable alloy of claim 8, wherein said additive material includes nickel, said nickel constitutes 0.15-0.4 wt. % of said dissolvable magnesium composite.

15. A dissolvable magnesium cast composite comprising a mixture of magnesium or a magnesium alloy and an additive material, said additive material includes a) nickel wherein said nickel constitutes 0.01-0.4 wt. % of said dissolvable magnesium cast composite, said dissolvable magnesium cast composite includes in situ precipitate, said in situ precipitate includes said additive material, said dissolvable magnesium cast composite has a dissolution rate of at least 75 mg/cm²/hr. in 3 wt. % KCl water mixture at 90° C.

16. The dissolvable alloy of claim 15, wherein said dissolvable magnesium composite has yield strength in a range of from about 25 to about 37 ksi.

17. The dissolvable alloy of claim 15, wherein said dissolvable magnesium composite has ultimate tensile strength in a range of from about 35 to about 45 ksi.

18. The dissolvable alloy of claim 15, wherein said dissolvable magnesium composite has an elongation in a range of from about 10 to about 19%.

19. The dissolvable alloy of claim 15, wherein said magnesium alloy comprises greater than 50 wt. % magnesium and no more than 10 wt. % aluminum, and one or more metals selected from the group consisting of 0.5-10 wt. % aluminum, 0.1-2 wt. % zinc, and 0.15-2 wt. % manganese.

20. The dissolvable alloy of claim 15, wherein said magnesium alloy comprises greater than 50 wt. % magnesium and no more than 10 wt. % aluminum, and one or more metals selected from the group consisting of 0.5-10 wt. % gadolinium, 0.1-6 wt. % yttrium, and 0.15-12 wt. % lithium.