CN102634711A - High-temperature high-toughness deformation magnesium alloy material and preparation method thereof - Google Patents

Abstract

The invention provides a high-temperature high-strength toughness deformed magnesium alloy material and a preparation method thereof. : According to the composition and mass percentage of the product: Y: 4.5-9.8%, Er: 0.5-1.5%, Ho: 0.3-1.0%, Zn: 3.0-4.5%, Zr: 0.2-0.6%, others Rare earth elements: 0.2-0.6%, the total amount of unavoidable Fe, Cu, Ni, Si impurities is less than 0.03%, and the balance is the ratio of Mg to prepare raw materials; the raw materials are commercially pure Mg, commercially pure Zn, Mg-RY intermediate Alloy, Mg-Zr intermediate alloy; after the raw material is melted, the smelting and slag removal process is carried out, and the temperature is lowered after the heat preservation and standing, and the rod is cast using a water-cooled mold; Press forming to obtain magnesium alloy products. The magnesium alloy material obtained by the method of the invention has high strength and high plasticity at room temperature. The cost of the invention is low, which is beneficial to popularization and application.

Description

A kind of high-temperature high-strength toughness deformation magnesium alloy material and preparation method thereof

technical field

The invention relates to a magnesium alloy material. The invention also relates to a preparation method of the magnesium alloy material.

Background technique

The outstanding advantage of magnesium alloy as a structural material is low density, but currently magnesium alloy materials generally have weaknesses such as low strength, high strength and low heat resistance, or high strength and low plasticity, which seriously hinders the application of magnesium alloys in aerospace, transportation and other fields. widely used. For example, AZ (mainly refers to AZ91) and AM (mainly refers to AM50, AM60) series cast magnesium alloys account for about 90% of the current magnesium alloys used in automobiles. They have appropriate room temperature strength, plasticity and good casting properties. AZ31 deformed magnesium alloys It is currently the most widely used wrought magnesium alloy commercially. It has good room temperature strength and good ductility. ZK60 and MB25 (domestic brands) are widely used high-strength wrought magnesium alloys at room temperature. However, the above AZ, AM, ZK and MB series magnesium alloys are only suitable for room temperature applications, and the mechanical properties of the alloys decrease sharply with the increase of temperature, which greatly limits their further applications. Alloying rare earth (RE) elements to improve the strength and heat resistance of magnesium alloys has been widely concerned by researchers. Studies have shown that Mg-RE1-RE2-Zr with high rare earth content represented by Mg-Gd-Y-Zr The alloy is currently the magnesium alloy with the highest strength and the best heat resistance developed by conventional methods. Its high-temperature strength and stability even exceed some high-temperature aluminum alloys. A large number of diffusely distributed nano-metastable phases precipitated during solid solution + aging treatment β' is the main reason for the improved strength and heat resistance of the alloy. However, this kind of high-strength heat-resistant magnesium alloy improves the strength and heat resistance of the alloy at the expense of alloy plasticity. For example, the tensile strength of the cast Mg-10Gd-5Y-Zr alloy in the T6 state is higher than 300 MPa at room temperature and 250 ° C, while it The elongation at room temperature is only 2%, and the elongation at 250°C only reaches 5% (Jun Wang, et al., Effect of Y for enhancing age hardening response and mechanical properties of Mg-Gd-Y-Zr alloys Mater.Sci. Eng.A, 2007 (456) 78-84), the room temperature tensile strength of T5 state hot-rolled Mg-10Gd-3Y-0.4Zr alloy is higher, reaching 460MPa, but the room temperature elongation is less than 0.5%. The tensile strength remains above 400MPa, but the elongation is only 6% (S.Kamado, Y.Kojima: Proc.of ^3rd International Magnesium Conference, ed.By GWLorimer, The Institute of Materials, London, 1997, 327- 342), high strength and heat resistance but poor plasticity are also not conducive to the practical application of magnesium alloys.

In addition, for the current addition method of rare earth, many scientific research institutes and manufacturers at home and abroad mostly add a single pure rare earth, such as Nd, Y, Gd, Dy, Er, Ho, La, Ce, etc. (Ce is also often added in the form of cerium-rich Mixed rare earth way to add). In fact, when selecting rare earths as alloy components of magnesium alloys, rare earth elements with large reserves and high distribution should be considered as much as possible, such as Ce and La in light rare earths and Y or Gd in heavy rare earths, so that the supply of raw materials is guaranteed. In order to achieve sustainable development, in addition, the price of raw materials and market conditions must also be considered, such as separating out the remaining Ce/La mixed rare earths from light rare earths with high value and good market Nd and Pr, and removing precious rare earths (Tb, Dy, Lu, etc.) after the remaining Y-rich rare earths, these rare earth raw materials are low in price, and the current application market is less. The above considerations are aimed at developing new high-performance magnesium alloy materials whose performance and cost can be accepted by the application market.

Contents of the invention

The object of the present invention is to provide a high-temperature high-strength toughness deformable magnesium alloy material with room temperature high strength and high plasticity. The purpose of the present invention is also to provide a method for preparing a high-temperature high-strength toughness deformed magnesium alloy material with low cost and favorable for popularization and application.

The high-temperature, high-strength and toughness deformable magnesium alloy material of the present invention has the following components and mass percentages: Y: 4.5-9.8%, Er: 0.5-1.5%, Ho: 0.3-1.0%, Zn: 3.0-4.5%, Zr: 0.2-0.6%, other rare earth elements: 0.2-0.6%, the total amount of unavoidable Fe, Cu, Ni, Si impurities is less than 0.03%, and the balance is Mg.

Among them, rare earth elements are added in the form of Mg-RY master alloy. The composition and mass percentage of RY are: Y: 75-82%, Er: 9-12%, Ho: 5-8%, and the balance is other rare earth elements.

The preparation method of the high-temperature high-strength toughness deformation magnesium alloy material of the present invention is as follows: according to the composition and mass percentage of the product: Y: 4.5-9.8%, Er: 0.5-1.5%, Ho: 0.3-1.0%, Zn : 3.0-4.5%, Zr: 0.2-0.6%, other rare earth elements: 0.2-0.6%, the total amount of unavoidable Fe, Cu, Ni, Si impurities is less than 0.03%, and the balance is the ratio of Mg to prepare raw materials; The raw materials are commercial pure Mg, commercial pure Zn, Mg-RY master alloy, and Mg-Zr master alloy; after the raw materials are melted, the smelting and slag removal processes are carried out, and the temperature is lowered after heat preservation and standing, and the rod is cast using a water-cooled mold; the obtained magnesium alloy rod After high-temperature homogenization treatment, the magnesium alloy product is obtained by hot extrusion on an extruder.

There are two protection methods in smelting: one is SF ₆ /CO ₂ gas protection, the other is flux protection;

Main smelting process parameters: the melt holding temperature is 750-770°C, the holding time is 25-45min, and the pouring temperature is 700-720°C;

Main process parameters of homogenization treatment: homogenization temperature is 450-500°C, holding time is 10-15h, and cooling method is air cooling.

Main hot extrusion process parameters: extrusion temperature is 420-470°C, extrusion speed is 1.2-1.5m/mim, in order to ensure high mechanical properties, the extrusion ratio must be greater than 15.

In the present invention, Y-rich rare earth (expressed as RY) is added to the magnesium alloy instead of pure rare earth, which not only reduces the cost of the alloy, but also has better material properties than alloys with pure rare earth, because Y-rich rare earth contains a certain amount of other Rare earth elements, such as Er, Ho, etc., the interaction of various rare earth elements can produce additional strengthening effects. In addition, cheap Zn, as the second main added element, works synergistically with rare earths to form a long-period stacked ordered structural phase with high thermal stability, high strength and toughness, so as to obtain a deformation with high strength and high plasticity at room temperature, high strength and high plasticity at high temperature Magnesium alloy material.

Substantive features and remarkable progress that the present invention has are:

(1) Studies have shown that a single heavy rare earth Y, Er, and Ho have excellent performance in improving the mechanical properties of magnesium alloys, especially high-temperature strength, but the price of a single rare earth is expensive, and it is difficult to popularize and apply, while two or more than two Heavy rare earth elements are better than single rare earth elements as alloying elements, which has been widely confirmed by researchers, such as Mg-Y-RE-based alloys (WE43, WE54) and Mg-Gd-RE-based alloys that have been developed or are being developed. In the present invention, rare earth elements are used as the first alloying element, and the rare earth raw material is Y-rich rare earth, which is mainly composed of heavy rare earth elements, wherein heavy rare earth Y is the main element, and other elements mainly include heavy rare earth Er and Ho, etc., and a variety of beneficial rare earth elements The interaction of elements can further improve the mechanical properties of the alloy, and the cost is much lower than that of adding a single rare earth. At the same time, the abundant Y-rich rare earth resources ensure the sustainable supply of the alloy, which is conducive to improving the competitiveness of magnesium alloys, thus Easier to promote applications.

(2) Using a suitable combination of rare earth and non-rare earth Zn as an alloying element can form a second phase and an ordered solid solution with a long-period stacking effective structure under specific casting, heat treatment and deformation processes. This long-period structure Compared with the crystal structure of the matrix, it has higher hardness, plasticity and elastic modulus, and it also has high thermal stability. Therefore, the existence of long-period structure can effectively improve the comprehensive mechanical properties and heat resistance of the alloy.

(3) With the change of RY and Zn element content, the room temperature tensile strength and elongation of the alloy of this invention vary by 340-420MPa according to different components and processes, and the elongation is 5-15%. The tensile strength can be maintained at 310-380MPa at high temperature, and the elongation is 18-29%, so that the alloy can meet the requirements of various applications by adjusting the content, proportion and process design of alloying elements.

Detailed ways

The technical solution of the present invention is described in detail below through specific examples. It should be understood that these examples are used to illustrate the present invention, rather than to limit the present invention. The present invention is simply improved under the concept of the present invention. All belong to the protection scope of the present invention.

Example 1

The chemical composition (mass percentage) of the alloy is: 5.8% RY, 4.0% Zn, 0.2% Zr, the total amount of impurity elements Fe, Cu, Ni, Si is less than 0.03%, and the balance is Mg.

The melting, casting and processing technology for preparing the alloy is as follows: first, weigh the materials according to the proportion, preheat Mg, Zn, Mg-RY master alloy, and Mg-Zr master alloy to 200°C, and then put Mg into the crucible preheated to 100°C and pass through the protective gas with a volume ratio of SF ₆ : CO ₂ of 1:100, add Zn after Mg is completely melted, and add Mg-RY master alloy when the melt temperature reaches 740°C, after the added master alloy is melted, When the melt temperature rises to 770°C, add Mg-Zr master alloy, pour in argon gas for refining and stirring for 10 minutes, after removing slag, let it stand at 750°C for 25 minutes, and when the temperature drops to 700°C, cast it into a round bar with a water-cooled mold. The obtained cast rods were homogenized at 450°C for 10 hours, then air-cooled, and then extruded at 420°C after turning with an extrusion rate of 1.5m/min, and finally a deformed magnesium alloy with high temperature, high strength and toughness was obtained.

The high-temperature high-strength toughness deformed magnesium alloy obtained in this embodiment has the following mechanical properties:

Room temperature: tensile strength: 372MPa, yield strength: 275MPa, elongation: 17%.

250°C: tensile strength: 315MPa, yield strength: 248MPa, elongation: 28%.

Example 2

The chemical composition (mass percentage) of the alloy is: 9.1% RY, 2.9% Zn, 0.4% Zr, the total amount of impurity elements Fe, Cu, Ni, Si is less than 0.03%, and the balance is Mg.

The melting, casting and processing technology for preparing the alloy is as follows: first, weigh the materials according to the proportion, preheat Mg, Zn, Mg-RY master alloy, and Mg-Zr master alloy to 250°C, and then put Mg into the crucible preheated to 120°C , and pass through a protective gas with a volume ratio of SF ₆ : CO ₂ of 1:100, add Zn after Mg is completely melted, and add Mg-RY master alloy when the melt temperature reaches 750°C, after the added master alloy is melted, When the melt temperature rises to 780°C, add Mg-Zr master alloy, pour in argon gas for refining and stirring for 15 minutes, after removing slag, let it stand at 760°C for 45 minutes, and after the temperature drops to 710°C, cast it into a round bar with a water-cooled mold. The obtained cast rods were homogenized at 480°C for 10 hours, then air-cooled, and then extruded at 450°C after turning with an extrusion rate of 1.5m/min. Finally, a high-temperature, high-strength and tough wrought magnesium alloy was obtained.

The high-temperature high-strength toughness deformed magnesium alloy obtained in this embodiment has the following mechanical properties:

Room temperature: tensile strength: 384MPa, yield strength: 297MPa, elongation: 12%.

250°C: tensile strength: 323MPa, yield strength: 254MPa, elongation: 29%.

Example 3

The chemical composition (mass percentage) of the alloy is: 9.4% RY, 4.4% Zn, 0.6% Zr, the total amount of impurity elements Fe, Cu, Ni, Si is less than 0.03%, and the balance is Mg.

The melting, casting and processing technology for preparing the alloy is as follows: first, weigh the materials according to the proportion, preheat Mg, Zn, Mg-RY master alloy, and Mg-Zr master alloy to 240°C, and then put Mg into the crucible preheated to 120°C and pass through the protective gas with a volume ratio of SF ₆ : CO ₂ of 1:100, add Zn after Mg is completely melted, and add Mg-RY master alloy when the melt temperature reaches 760°C, after the added master alloy is melted, When the melt temperature rises to 780°C, add Mg-Zr master alloy, pour in argon gas for refining and stirring for 15 minutes, after removing slag, let stand at 770°C for 30 minutes, and when the temperature drops to 720°C, cast it into a round bar with a water-cooled mold. The obtained cast rods were homogenized at 480°C for 15 hours, then air-cooled, and then extruded at 450°C after turning at a extrusion rate of 1.2m/mim. Finally, a deformed magnesium alloy with high temperature, high strength and toughness was obtained.

The high-temperature high-strength toughness deformed magnesium alloy obtained in this embodiment has the following mechanical properties:

Room temperature: tensile strength: 421MPa, yield strength: 344MPa, elongation: 11%.

250°C: tensile strength: 346MPa, yield strength: 271MPa, elongation: 25%.

Example 4

The chemical composition (mass percentage) of the alloy is: 12.3% RY, 4.5% Zn, 0.3% Zr. The total amount of impurity elements Fe, Cu, Ni and Si is less than 0.03%, and the balance is Mg.

The melting, casting and processing technology for preparing the alloy is as follows: first, weigh the materials according to the proportion, preheat the Mg, Zn, Mg-RY master alloy, and Mg-Zr master alloy to 250°C, then put Mg into the crucible containing the melted solvent, Add Zn after Mg is completely melted, add Mg-RY master alloy when the melt temperature reaches 760°C, add Mg-Zr master alloy when the melt temperature rises to 780°C after the added master alloy is melted, and add refining Refining and stirring for 15 minutes. After removing the slag, let it stand at 740°C for 40 minutes. After the temperature drops to 720°C, cast it into a round rod with a water-cooled mold. The obtained cast rods were homogenized at 500°C for 15 hours, then air-cooled, and then extruded at 470°C after turning with an extrusion rate of 1.2m/min. Finally, a high-temperature, high-strength and tough wrought magnesium alloy was obtained.

The high-temperature high-strength toughness deformed magnesium alloy obtained in this embodiment has the following mechanical properties:

Room temperature: tensile strength: 340MPa, yield strength: 265MPa, elongation: 5%.

250°C: tensile strength: 389MPa, yield strength: 344MPa, elongation: 18%.

Claims (7)

1. the tough deformed magnesium alloy material of high strength at high temperature is characterized in that moity and quality percentage composition thereof are: Y4.5-9.8%, Er 0.5-1.5%; Ho 0.3-1.0%; Zn 3.0-4.5%, Zr 0.2-0.6%, other REE 0.2-0.6%; Inevitably Fe, Cu, Ni, Si total impurities are less than 0.03%, and surplus is Mg.

2. the tough deformed magnesium alloy material of high strength at high temperature according to claim 1; It is characterized in that: wherein REE is that mode with the Mg-RY master alloy adds, and RY moity and quality percentage composition thereof are: Y:75-82%, Er:9-12%; Ho:5-8%, surplus is other REEs.

3. the preparation method of the tough deformed magnesium alloy material of high strength at high temperature is characterized in that: according to moity in the product and quality percentage composition thereof be: Y:4.5-9.8%, Er:0.5-1.5%; Ho:0.3-1.0%; Zn:3.0-4.5%, Zr:0.2-0.6%, other REE: 0.2-0.6%; Inevitably Fe, Cu, Ni, Si total impurities are less than 0.03%, and surplus is the ratio preparation raw material of Mg; Said raw material is commercially pure Mg, commercially pure Zn, Mg-RY master alloy, Mg-Zr master alloy; Raw material carries out melting after melting, the operation of skimming, and the back cooling is left standstill in insulation, utilizes the water-cooled mould to cast rod; After gained casting of magnesium alloy rod is handled through the high temperature homogeneity, the hot-pressed magnesium-alloy material that obtains on extrusion machine.

4. the preparation method of the tough deformed magnesium alloy material of high strength at high temperature according to claim 3 is characterized in that: protected mode is SF in the melting ₆/ CO ₂Gas shield, or flux protection.

5. the preparation method of the tough deformed magnesium alloy material of high strength at high temperature according to claim 4, it is characterized in that main melting technology parameter is: the melt holding temperature is 750-770 ℃, and the insulation time of repose is 25-45min, and teeming temperature is 700-720 ℃.

6. the preparation method of the tough deformed magnesium alloy material of high strength at high temperature according to claim 5, it is characterized in that main homogeneity treatment process parameter is: homogenization temperature is 450-500 ℃, and soaking time is 10-15h, and the type of cooling is an air cooling.

7. the preparation method of the tough deformed magnesium alloy material of high strength at high temperature according to claim 3; It is characterized in that main hot extrusion technique parameter is: extrusion temperature is 420-470 ℃; Extruding rate is 1.2-1.5m/mim, and for guaranteeing strong mechanical performance, extrusion ratio needs greater than 15.