CN104073702A - Rear-earth magnesium alloy and preparation method thereof - Google Patents

Abstract

A rare earth magnesium alloy and a preparation method thereof belong to the technical field of metal materials. The technical problem of high preparation cost of AE44 in the prior art is solved, and the room-temperature mechanical properties, high-temperature mechanical properties and high-temperature creep properties of the Mg-Al-RE alloy are further improved. The composition and mass percentage of the rare earth magnesium alloy of the present invention are: Al: 3.4-4.4%; La: 2.5-4.0%; Sr: 0.1-1.2%; Mn: 0.2-0.4%; B: 0.01-0.2%; for magnesium. The present invention also provides a preparation method of the above-mentioned rare earth magnesium alloy. The rare earth magnesium alloy has excellent high-temperature mechanical properties and high-temperature creep properties. At 200°C, the tensile strength is 110-120MPa, the yield strength is 90-100MPa, and the elongation is 17-22%. Under these conditions, the creep deformation of 150h is 0.83%.

Description

A kind of rare earth magnesium alloy and preparation method thereof

technical field

The invention relates to a rare earth magnesium alloy and a preparation method thereof, belonging to the technical field of metal materials.

Background technique

Magnesium and magnesium alloys are currently the metal structural materials with the lowest density in engineering applications, and they also have easy recycling, high specific strength, high specific stiffness, high damping performance, good electromagnetic shielding performance, and excellent casting and machining performance, etc. Advantages, it has important application value and broad application prospects in the fields of automobile, 3C, aerospace, military industry and national defense. In industrial production, the most widely used magnesium alloys are cast magnesium alloys, especially die cast magnesium alloys, including AZ (Mg-Al-Zn) series, AM (Mg-Al-Mn) series, AS (Mg-Al-Si ) series and AE (Mg-Al-RE) series etc. Among them, the AZ series and AM series die-casting magnesium alloys have been applied to a certain extent in the automotive industry due to their excellent die-casting properties and high room temperature mechanical properties, but their high temperature properties and creep properties are poor, so their applications are generally limited to An environment with a temperature below 120°C. However, the working temperature of automobile transmission parts is generally 150-200°C, so the development of heat-resistant magnesium alloys has become an inevitable trend in the development of magnesium alloys.

DowMagnesium forms thermodynamically stable Al ₁₁ RE ₃ and Al ₂ RE phases by adding cerium-rich rare earth (RE) to Mg-Al alloys, thereby inhibiting the precipitation of Mg ₁₇ Al ₁₂ and developing a new alloy with good high temperature performance and creep resistance. Variable performance AE42 die-cast magnesium alloy. However, when the temperature is higher than 150 °C, the supersaturated aluminum in the AE42 alloy will react with magnesium to form Mg ₁₇ Al ₁₂ phase, which will lead to a sharp decline in its high-temperature mechanical properties and creep resistance. In 2005, the Norwegian Hydro Magnesium Company developed the heat-resistant die-casting magnesium alloy AE44 by increasing the content of rare earths. , the mass percentage of Ce is 55%, the mass percentage of La is 25%, the mass percentage of Nd is 15%, and the mass percentage of Pr is 5%), compared with AE42 alloy, AE44 has 2% more rare earth content, using the increased rare earth content to form more Al-RE second phases to increase the creep performance of the alloy. However, since Nd, Pr and other rare earths have been widely used in NdFeB permanent magnet materials in recent years, the prices of Nd and Pr have risen sharply, more than ten times the price of La and Ce, and have been separated from cerium-rich rare earths. This leads to the high cost of the AE44 alloy; and even though the room temperature mechanical properties, high temperature mechanical properties and high temperature creep properties of AE44 have been improved, the optimal effect has not yet been achieved.

Contents of the invention

In order to solve the technical problem of high preparation cost of AE44 in the prior art and further improve the room-temperature mechanical properties, high-temperature mechanical properties and high-temperature creep properties of Mg-Al-RE alloys, the invention provides a rare earth magnesium alloy and a preparation method thereof.

Composition and mass percent of the rare earth magnesium alloy of the present invention are:

Al: 3.4%-4.4%;

La: 2.5%-4.0%;

Sr: 0.1%-1.2%;

Mn: 0.2%-0.4%;

B: 0.01%-0.2%;

The balance is magnesium.

Preferably, the composition and mass percentage are:

Al: 3.7%-4.0%;

La: 3.0%-4.0%;

Sr: 0.4%-0.8%;

Mn: 0.3%-0.4%;

B: 0.04%-0.07%;

The balance is magnesium.

The preparation method of the above-mentioned rare earth magnesium alloy comprises the following steps:

(1) under the action of protective gas, magnesium, aluminum and magnesium-manganese master alloy are melted to obtain the first melt;

(2) Under the action of protective gas, after the first melt is heated up, magnesium-lanthanum master alloy, magnesium-strontium master alloy and aluminum-boron master alloy are added to the first melt, and after stirring, argon gas is introduced to obtain the second melt. melt;

(3) Put the second melt obtained in step (2) to stand to cool down, and then die-cast to obtain a rare earth magnesium alloy.

Preferably, in the step (1), the melting temperature is 660-680°C.

Preferably, in the step (2), the heating temperature is 730-740°C.

Preferably, in the step (2), the stirring speed is 100-300 rpm, and the stirring time is 5-10 min.

Preferably, in the step (2), after stirring for 5-10 minutes, it is left to stand at a constant temperature of 730° C.-740° C. for 15-20 minutes, and then argon gas is introduced.

Preferably, in the step (2), the flow rate of feeding nitrogen is 2-5 L/min, and the time is 5-8 min.

Preferably, in the step (3), the cooling temperature is 700-720°C.

Preferably, in the magnesium-lanthanum master alloy, the mass percentage of magnesium is 75-85%, and that of lanthanum is 15-25%; in the magnesium-strontium master alloy, the mass percentage of magnesium is 75-85%, and that of strontium is The mass percentage is 15-25%; in the magnesium-manganese master alloy, the mass percentage of magnesium is 92-97%, the mass percentage of manganese is 3-8%; in the aluminum-boron master alloy, the mass percentage of aluminum is 92-97%, The mass percentage of boron is 3-8%.

Compared with prior art, the beneficial effect of the present invention:

(1) The rare earth magnesium alloy of the present invention forms Al ₁₁ La ₃ phase and Al ₄ Sr phase through the combination of lanthanum and strontium with aluminum in the alloy, which suppresses the generation of Mg ₁₇ Al ₁₂ phase, and utilizes Al ₁₁ La ₃ phase and Al 12 phase at the same time The high-temperature thermal stability of the Al ₄ Sr phase improves the high-temperature mechanical properties and creep properties of the alloy. Experimental results show that the tensile strength of the rare earth magnesium alloy of the present invention is 240-250MPa at room temperature, and the yield strength is 155-165MPa. The elongation is 6-9%, the tensile strength is 140-150MPa at 150°C, the yield strength is 105-115MPa, the elongation is 18-25%, and the tensile strength is 110-120MPa at 200°C , the yield strength is 90-100MPa, the elongation is 17-22%; under the condition of 150℃/85MPa, the creep deformation of 250h is 0.30%, and under the condition of 200℃/85MPa, the creep deformation of 150h is 0.83%;

(2) The rare earth magnesium alloy of the present invention uses strontium and boron to change the morphology and shape of the crystal grains, reduce the grain size, play a role in refining the grains, and make the second phase transformation in the microstructure of the alloy It is relatively small and has several different shapes at the same time, which reduces the stress concentration of the alloy at the grain boundary during the deformation process, which is conducive to improving the strength and plastic deformation capacity of the alloy, and further improves the mechanical properties of the alloy at room temperature. The experimental results It shows that the average grain size of the rare earth magnesium alloy of the present invention is 20-60 μm;

(3) The rare earth magnesium alloy of the present invention can react with iron or other impurity elements in the melt to form compounds through manganese and boron elements and sink into the bottom of the furnace to be removed in the form of slag, thereby reducing the harmful impurity content in the alloy and improving the alloy. anti-corrosion properties;

(4) The aluminum in the rare earth magnesium alloy of the present invention makes the alloy have balanced strength, plasticity and casting process performance, making the rare earth magnesium alloy of the present invention suitable for industrial mass production;

(5) In the process of the preparation method of the rare earth magnesium alloy of the present invention, an appropriate amount of rare earth elements can be degassed and refined and purify the alloy melt, and also ensure the anti-oxidation and flame-retardant effects of the alloy in the smelting process, and ensure the alloy smelting the quality of;

(6) In the process of the preparation method of the rare earth magnesium alloy of the present invention, the rare earth magnesium alloy material is made denser by high-pressure casting, and the number of grains and the second phase is larger and the size is smaller, thereby further improving the alloy's High temperature mechanical properties and creep properties.

Description of drawings

Fig. 1 is the metallographic (OM) micrograph of the rare earth magnesium alloy prepared by the embodiment of the present invention 3;

Fig. 2 is a scanning electron microscope (SEM) back electron scattering micrograph of the rare earth magnesium alloy prepared in Example 3 of the present invention.

Detailed ways

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with specific embodiments, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the claims of the present invention.

The composition and mass percentage of the rare earth magnesium alloy of the present invention are: 3.4%-4.4% Al, 2.5%-4.0% La, 0.1%-1.2% Sr, 0.2%-0.4% Mn, 0.01%-0.2% For B, the total amount is less than 0.02% impurity elements Fe, Cu, Si and Ni (generally, unavoidable doping impurities Fe, Cu, Si and Ni during the smelting process), and the balance is Mg.

The rare earth magnesium alloy of the present invention has a tensile strength of 240-250MPa at room temperature, a yield strength of 155-165MPa, and an elongation of 6-9%; and a tensile strength of 140-150MPa at 150°C, and a yield strength of 105 -115MPa, the elongation is 18-25%; the tensile strength is 110-120MPa at 200°C, the yield strength is 90-100MPa, and the elongation is 17-22%; and at 150°C/85MPa, 250h The creep deformation is 0.30%; under the condition of 200℃/85MPa, the creep deformation of 150h is 0.83%. The average grain size of the rare earth magnesium alloy of the present invention is 20-60 μm.

The room temperature in the present invention is a temperature well known to those skilled in the art, and generally may be 20-25°C.

The present invention has no special restrictions on the source of Al in the rare earth magnesium alloy, and the source of Al known to those skilled in the art can be used. The purity of Al can be the purity known to be used by those skilled in the art to prepare the rare earth magnesium alloy. Generally, pure aluminum is used. The purity is above 99.5%. The Al in the rare earth magnesium alloy of the invention makes the alloy have balanced strength, plasticity and casting process performance, and is suitable for industrial batch production.

The present invention has no special limitation on the source of Mg in the rare earth magnesium alloy. The source of Mg known to those skilled in the art can be used. The purity of Mg can be the purity known to be used by those skilled in the art to prepare the rare earth magnesium alloy. Generally, pure magnesium is used. The purity is above 99.5%.

The present invention has no special limitation on the source of La in the rare earth magnesium alloy. The sources of rare earth elements known to those skilled in the art or commercially available rare earth elements can be used. The purity of La is the purity of rare earth elements known to those skilled in the art to prepare rare earth magnesium alloys. That's it.

The present invention has no special restrictions on the sources of Sr, Mn and B in the rare earth magnesium alloy, and the sources known to those skilled in the art can be used, and the purity can also be the purity known to be used by those skilled in the art to prepare rare earth magnesium alloys.

In the present invention, lanthanum and strontium can combine with aluminum in the alloy to form Al ₁₁ La ₃ phase and Al ₄ Sr phase, thereby inhibiting the formation of Mg ₁₇ Al ₁₂ phase, while Al ₁₁ La ₃ phase and Al ₄ Sr phase are both The high-temperature thermally stable phase makes the prepared alloy have excellent high-temperature heat resistance and high-temperature creep properties. Compared with the prior art, the melting point and stability of the second phase formed by aluminum and lanthanum are higher than those of cerium, neodymium and praseodymium, and the solid solubility in magnesium alloy is 0.4wt%La<0.74wt%Ce<1.7 wt%Pr<3.6wt%Nd, the greater the solid solubility of elements in the alloy and the more dissolved, the less the rare earth content that forms the second phase, that is to say, Nd and Pr form The heat-resistant second phase of the alloy is less, and the creep performance is relatively poor, so the present invention uses rare earth lanthanum to replace the cerium-rich rare earth to maximize the creep performance of the alloy.

In the present invention, the addition of strontium and boron changes the morphology and shape of the grains, reduces the grain size, plays a role in refining the grains, enhances the strength and plasticity of the alloy, and makes the microstructure of the alloy The second phase transition in the medium is relatively small, and has several different shapes at the same time, which reduces the stress concentration at the grain boundary during the deformation of the alloy, thereby improving the strength and plastic deformation capacity of the alloy, and further improving the mechanical properties of the alloy at room temperature.

In the present invention, manganese and boron can react with iron or other elements in the melt to form compounds and sink to the bottom of the furnace to be removed in the form of slag, thereby reducing the content of harmful impurities in the alloy and improving the corrosion resistance of the alloy.

The preparation method of the rare earth magnesium alloy of the present invention comprises the following steps:

(1) Under the action of protective gas, magnesium, aluminum and magnesium-manganese master alloys are added to a melting device and melted at 660-680° C. to obtain a first melt;

(2) Under the action of protective gas, after raising the temperature of the first melt to 730-740°C, add magnesium-lanthanum master alloy, magnesium-strontium master alloy and aluminum-boron master alloy to the first melt, and keep the temperature at 730-740°C ℃, after stirring at 100-300 rpm for 5-10min, then standing at a constant temperature of 730-740℃ for 15-20min, and then refining with argon gas at a flow rate of 2-5L/min for 5-8min to obtain the second melt;

Among them, stirring can promote the uniform distribution of each alloy element. If the stirring time is less than 5-10 minutes, segregation is prone to occur. If the stirring time is higher than 5-10 minutes, the contact between the melt and air may cause oxidation inclusions, such as magnesium oxide, etc. So the stirring time of the present invention is preferably 5-10min;

(3) cooling the second melt obtained in step (2) to 700-720° C., the cooling process generally takes 35-40 minutes, and then die-casting to obtain a rare earth magnesium alloy;

Among them, die-casting is known to those skilled in the art as high pressure diecasting (high pressure diecasting), referred to as die-casting, the use of die-casting can make the rare earth magnesium alloy of the present invention denser, have fewer pores, and have higher strength, stiffness and other properties. In the preparation method of the present invention , Die-casting can be performed on a cold chamber die-casting machine with a clamping force of 180-580 tons.

In the preparation method of the present invention, the amount of magnesium, aluminum, magnesium-lanthanum master alloy, magnesium-strontium master alloy, magnesium-manganese master alloy and aluminum-boron master alloy is based on the composition and mass percentage ratio of the rare earth magnesium alloy to be prepared. The process is not particularly limited, and it can be done according to methods known to those skilled in the art, and loss is generally not considered. Among them, part of the magnesium in the rare earth magnesium alloy comes from the directly added magnesium, and the other part comes from the magnesium lanthanum master alloy, magnesium strontium master alloy and magnesium manganese master alloy, part of the aluminum in the rare earth magnesium alloy comes from the directly added aluminum, and the other Part of it comes from the aluminum-boron master alloy.

In the magnesium-lanthanum master alloy of the present invention, the mass percentage of magnesium is preferably 75-85%, the mass percentage of lanthanum is preferably 15-25%; the magnesium-manganese master alloy, the mass percentage of magnesium is preferably 92-97%, and the mass percentage of manganese Percentage is preferably 3-8%; Magnesium-strontium master alloy, the mass percent of magnesium is preferably 75-85%, the mass percent of strontium is preferably 15-25%; In aluminum-boron master alloy, the mass percent of aluminum is preferably 92- 97%, the mass percentage of boron is preferably 3-8%. Magnesium-lanthanum master alloys, magnesium-strontium master alloys, magnesium-manganese master alloys and aluminum-boron master alloys are all raw materials known to those skilled in the art and can be purchased commercially.

In the present invention, the magnesium, aluminum, magnesium-lanthanum master alloy, magnesium-strontium master alloy, magnesium-manganese master alloy and aluminum-boron master alloy are preferably preheated to 200-300° C. before melting in a melting device. The melting device of the present invention is not particularly limited, generally a known magnesium alloy melting crucible can be used. Preferably, the melting device is preheated to 300°C.

In the preparation method of the present invention, the protective gas in step (1) and step (2) is SF ₆ :CO ₂ with a volume ratio of 1:100.

The present invention is further described below in conjunction with embodiment and accompanying drawing.

Example 1

The composition and mass percentage of the rare earth magnesium alloy are: 3.4% aluminum, 2.5% lanthanum, 0.1% strontium, 0.2% manganese, 0.01% boron, and the balance is magnesium.

The preparation of above-mentioned rare earth magnesium alloy:

(1) According to the composition and mass percentage ratio of the above-mentioned rare earth magnesium alloy, the mass percentage of magnesium (purity 99.8%) is 79.59%, the mass percentage of aluminum (purity 99.5%) is 3.21%, magnesium-lanthanum master alloy (magnesium 80%, lanthanum 20%) with a mass percentage of 12.5%, magnesium-strontium master alloy (magnesium 80%, strontium 20%) with a mass percentage of 0.5%, magnesium-manganese master alloy (magnesium 95%, manganese The mass percentage of 5%) is 4%, and the mass percentage of aluminum-boron master alloy (aluminum accounts for 95%, boron accounts for 5%) is 0.2%;

(2) Preheating magnesium, aluminum, magnesium-lanthanum master alloy, magnesium-strontium master alloy, magnesium-manganese master alloy and aluminum-boron master alloy to 200-300°C;

(3) Put the preheated magnesium, aluminum and magnesium-manganese master alloy into a crucible preheated to 300°C, and heat it to 660-680°C under the protection of SF ₆ :CO ₂ with a volume ratio of 1:100 ℃, after the magnesium, aluminum and magnesium-manganese intermediate alloys are completely melted, the first melt is obtained;

(4) Under the protection of SF6:CO2 with a volume ratio of 1:100, raise the temperature of the first melt to 730-740°C, and add the preheated magnesium-lanthanum master alloy, magnesium-strontium master alloy and aluminum-boron master alloy The alloy is kept at 730-740°C, stirred at a speed of 100-300 rpm for 5-10 minutes, kept at 730-740°C for 15-20 minutes, and then refined with argon for 5-8 minutes to obtain the second melt;

(5) cooling the second melt to 700-720° C., and performing die-casting on a cold-chamber die-casting machine with a clamping force of 580 tons to obtain a rare earth magnesium alloy.

At room temperature and high temperature, according to GB/T228.1-2010 Tensile test of metal materials Part 1: Room temperature test method and GB/T2039-1997 Metal tensile creep and durability test method, the rare earth magnesium alloy is tensile tested And creep test, the test results are shown in Table 2-Table 7.

Example 2

The composition and mass percentage of the rare earth magnesium alloy are: 3.7% aluminum, 3.0% lanthanum, 0.4% strontium, 0.3% manganese, 0.04% boron, and the balance is magnesium.

The preparation of above-mentioned rare earth magnesium alloy:

(1) According to the composition and mass percentage ratio of the above-mentioned rare earth magnesium alloy, the mass percentage of magnesium (purity 99.8%) is 73.26%, the mass percentage of aluminum (purity 99.5%) is 2.94%, magnesium-lanthanum master alloy (magnesium 80%, lanthanum 20%) is 15% by mass, magnesium-strontium master alloy (magnesium 80%, strontium 20%) is 2%, magnesium-manganese master alloy (magnesium 95%, manganese 5%) is 6% by mass, and the mass percentage of aluminum-boron master alloy (aluminum accounts for 95%, boron accounts for 5%) is 0.8%;

(2) Preheating magnesium, aluminum, magnesium-lanthanum master alloy, magnesium-strontium master alloy, magnesium-manganese master alloy and aluminum-boron master alloy to 200-300°C;

(3) Put the preheated magnesium, aluminum and magnesium-manganese master alloy into a crucible preheated to 300°C, and heat it to 660-680°C under the protection of SF ₆ :CO ₂ with a volume ratio of 1:100 ℃, after the magnesium, aluminum and magnesium-manganese intermediate alloys are completely melted, the first melt is obtained;

(4) Under the protection of SF6:CO2 with a volume ratio of 1:100, raise the temperature of the first melt to 730-740°C, and add the preheated magnesium-lanthanum master alloy, magnesium-strontium master alloy and aluminum-boron master alloy The alloy is kept at 730-740°C, stirred at a speed of 100-300 rpm for 5-10 minutes, kept at 730-740°C for 15-20 minutes, and then refined with argon for 5-8 minutes to obtain the second melt;

(5) cooling the second melt to 700-720° C., and performing die-casting on a cold-chamber die-casting machine with a clamping force of 580 tons to obtain a rare earth magnesium alloy.

At room temperature and high temperature, according to GB/T228.1-2010 Tensile test of metal materials Part 1: Room temperature test method and GB/T2039-1997 Metal tensile creep and durability test method, the rare earth magnesium alloy is tensile tested And creep test, the test results are shown in Table 2-Table 7.

Example 3

The composition and mass percentage of the rare earth magnesium alloy are: 4.0% aluminum, 4.0% lanthanum, 0.8% strontium, 0.3% manganese, 0.07% boron, and the balance is magnesium.

The preparation of above-mentioned rare earth magnesium alloy:

(1) According to the composition and mass percentage proportioning of the above-mentioned rare earth magnesium alloy, the mass percentage of magnesium (purity 99.8%) is 65.93%, the mass percentage of aluminum (purity 99.5%) is 2.67%, magnesium-lanthanum master alloy (magnesium 80%, lanthanum 20%) is 20% by mass, magnesium-strontium master alloy (magnesium 80%, strontium 20%) is 4%, magnesium-manganese master alloy (magnesium 95%, manganese 5%) is 6% by mass, and the mass percentage of aluminum-boron master alloy (aluminum accounts for 95%, boron accounts for 5%) is 1.4%;

(2) Preheating magnesium, aluminum, magnesium-lanthanum master alloy, magnesium-strontium master alloy, magnesium-manganese master alloy and aluminum-boron master alloy to 200-300°C;

(3) Put the preheated magnesium, aluminum and magnesium-manganese master alloy into a crucible preheated to 300°C, and heat it to 660-680°C under the protection of SF ₆ :CO ₂ with a volume ratio of 1:100 ℃, after the magnesium, aluminum and magnesium-manganese intermediate alloys are completely melted, the first melt is obtained;

(4) Under the protection of SF ₆ :CO ₂ with a volume ratio of 1:100, raise the temperature of the first melt to 730-740°C, and add the preheated magnesium-lanthanum master alloy, magnesium-strontium master alloy and aluminum Boron intermediate alloy, keep at 730-740°C, stir at 100-300 rpm for 5-10min, keep it at 730-740°C for 15-20min, and then refine with argon for 5-8min to obtain the second melt ;

(5) cooling the second melt to 700-720° C., and performing die-casting on a cold-chamber die-casting machine with a clamping force of 580 tons to obtain a rare earth magnesium alloy.

Fig. 1 is the metallographic micrograph of the rare earth magnesium alloy prepared by the embodiment of the present invention 3, as can be seen from Fig. 1, the rare earth magnesium alloy grain size of the present invention is 20-60 μ m; Fig. 2 is the rare earth prepared by the embodiment of the present invention 3 The scanning electron microscope back electron scattering micrograph of magnesium alloy, as can be seen from Fig. 2, the rare earth magnesium alloy of the present invention exists Al ₁₁ La ₃ high-temperature thermally stable phase (white acicular phase on the grain boundary), Al ₄ Sr high-temperature thermally stable phase phase (a small amount distributed in the grain boundary and intragranular white massive phase), these two phases have very high melting points, 1240°C and 1040°C respectively, both of which are higher than the network Mg ₁₇ Al ₁₂ phase existing on the grain boundary in the alloy The melting point is 455°C, which improves the high-temperature mechanical properties and creep properties of the alloy.

According to the determination of GB/T20125-2006 low alloy steel multielement, the chemical composition of the rare earth magnesium alloy of embodiment 3 measured by inductively coupled plasma emission spectrometry is as shown in table 1:

Table 1 is the composition of the rare earth magnesium alloy prepared in embodiment 3

Alloy main element wt% Impurity elements wt%

Al La Sr mn B margin Fe Si Cu Ni Total 3.98 3.85 0.74 0.28 0.068 Mg 0.005 0.01 0.001 0.0001 <0.02

As can be seen from Table 1, embodiment 3 has indeed prepared components and mass percent is: 4.0% aluminum, 4.0% lanthanum, 0.8% strontium, 0.3% manganese, 0.07% boron, and the balance is magnesium. Rare earth magnesium alloys.

At room temperature and high temperature, according to GB/T228.1-2010 Tensile test of metal materials Part 1: Room temperature test method and GB/T2039-1997 Metal tensile creep and durability test method, the rare earth magnesium alloy is tensile tested And creep test, the test results are shown in Table 2-Table 7.

Example 4

The composition and mass percentage of the rare earth magnesium alloy are: 4.4% aluminum, 3.5% lanthanum, 1.2% strontium, 0.4% manganese, 0.2% boron, and the balance is magnesium.

The preparation of above-mentioned rare earth magnesium alloy:

(1) According to the composition and mass percentage ratio of the above-mentioned rare earth magnesium alloy, the mass percentage of magnesium (purity 99.8%) is 63.90%, the mass percentage of aluminum (purity 99.5%) is 0.6%, the magnesium-lanthanum master alloy (magnesium 80%, lanthanum 20%) is 17.5% by mass, magnesium-strontium master alloy (magnesium 80%, strontium 20%) is 6%, magnesium-manganese master alloy (magnesium 95%, manganese 5%) is 8% by mass, and the mass percentage of aluminum-boron master alloy (aluminum accounts for 95%, boron accounts for 5%) is 4%;

(2) Preheating magnesium, aluminum, magnesium-lanthanum master alloy, magnesium-strontium master alloy, magnesium-manganese master alloy and aluminum-boron master alloy to 200-300°C;

(3) Put the preheated magnesium, aluminum and magnesium-manganese master alloy into a crucible preheated to 300°C, and heat it to 660-680°C under the protection of SF ₆ :CO ₂ with a volume ratio of 1:100 ℃, after the magnesium, aluminum and magnesium-manganese intermediate alloys are completely melted, the first melt is obtained;

(4) Under the protection of SF ₆ :CO ₂ with a volume ratio of 1:100, raise the temperature of the first melt to 730-740°C, and add the preheated magnesium-lanthanum master alloy, magnesium-strontium master alloy and aluminum Boron intermediate alloy, keep at 730-740°C, stir at 100-300 rpm for 5-10min, keep it at 730-740°C for 15-20min, and then refine with argon for 5-8min to obtain the second melt ;

(5) cooling the second melt to 700-720° C., and performing die-casting on a cold-chamber die-casting machine with a clamping force of 580 tons to obtain a rare earth magnesium alloy.

At room temperature and high temperature, according to GB/T228.1-2010 Tensile test of metal materials Part 1: Room temperature test method and GB/T2039-1997 Metal tensile creep and durability test method, the rare earth magnesium alloy is tensile tested And creep test, the test results are shown in Table 2-Table 7.

Table 2 is the mechanical properties of the rare earth magnesium alloys of Examples 1-4 at room temperature (20°C)

Table 3 is the mechanical properties of the rare earth magnesium alloys of Examples 1-4 at high temperature (150°C)

Table 4 is the mechanical properties of the rare earth magnesium alloys of Examples 1-4 at high temperature (200°C)

Table 5 is the mechanical properties of the rare earth magnesium alloys of Examples 1-4 at high temperature (250°C)

Table 6 is the high temperature (150°C) creep properties of the rare earth magnesium alloys of Examples 1-4

Table 7 shows the high temperature (200°C) creep properties of the rare earth magnesium alloys of Examples 1-4

It can be seen from Table 2 to Table 7 that the rare earth magnesium alloy of the present invention has excellent room temperature mechanical properties, high temperature mechanical properties and high temperature creep properties.

Apparently, the descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those of ordinary skill in the technical field, without departing from the principles of the present invention, some improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention .

Claims (10)

1. A rare earth magnesium alloy, characterized in that, the composition and mass percentage of the rare earth magnesium alloy are: Al: 3.4%-4.4%; La: 2.5%-4.0%; Sr: 0.1%-1.2%; Mn: 0.2%-0.4%; B: 0.01%-0.2%; The balance is magnesium. 2. a kind of rare earth magnesium alloy according to claim 1, is characterized in that, described composition and mass percent are: Al: 3.7%-4.0%; La: 3.0%-4.0%; Sr: 0.4%-0.8%; Mn: 0.3%-0.4%; B: 0.04%-0.07%; The balance is magnesium. 3. the preparation method of a kind of rare earth magnesium alloy described in claim 1 or 2 is characterized in that, comprises the following steps: (1) under the action of protective gas, magnesium, aluminum and magnesium-manganese master alloy are melted to obtain the first melt; (2) Under the action of protective gas, after the first melt is heated up, magnesium-lanthanum master alloy, magnesium-strontium master alloy and aluminum-boron master alloy are added to the first melt, and after stirring, argon gas is introduced to obtain the second melt. melt; (3) Put the second melt obtained in step (2) to stand to cool down, and then die-cast to obtain a rare earth magnesium alloy. 4. The preparation method of a rare earth magnesium alloy according to claim 3, characterized in that, in the step (1), the melting temperature is 660-680°C. 5 . The preparation method of a rare earth magnesium alloy according to claim 3 , characterized in that, in the step (2), the heating temperature is 730-740° C. 6. The preparation method of a rare earth magnesium alloy according to claim 3, characterized in that, in the step (2), the stirring speed is 100-300 rpm, and the stirring time is 5-10 min. 7. The preparation method of a rare earth magnesium alloy according to claim 3, characterized in that, in the step (2), after stirring, it is left to stand at a constant temperature of 730-740°C for 15-20min, and then argon gas is introduced . 8. The preparation method of a rare earth magnesium alloy according to claim 3, characterized in that, in the step (2), the flow rate of the nitrogen gas is 2-5L/min, and the time is 5-8min. 9. The preparation method of a rare earth magnesium alloy according to claim 3, characterized in that, in the step (3), the cooling temperature is 700-720°C. 10. The preparation method of a rare earth magnesium alloy according to claim 3, characterized in that, in the magnesium-lanthanum master alloy, the mass percentage of magnesium is 75-85%, and the mass percentage of lanthanum is 15-25%; In the magnesium-strontium master alloy, the mass percentage of magnesium is 75-85%, and the mass percentage of strontium is 15-25%; in the magnesium-manganese master alloy, the mass percentage of magnesium is 92-97%, and the mass percentage of manganese is 3-8 %; in the aluminum-boron master alloy, the mass percentage of aluminum is 92-97%, and the mass percentage of boron is 3-8%.