CN105039817B - The preparation method and multicomponent heat-resistant magnesium alloy of a kind of multicomponent heat-resistant magnesium alloy - Google Patents

Abstract

The invention discloses a preparation method of a multi-element heat-resistant magnesium alloy and the multi-element heat-resistant magnesium alloy. The method comprises the following steps: 1) the cast magnesium alloy is composed of the following components in mass percentage: Al 7.5-8.5%, Zn 0.8-1.2%, RE 1.2-2.4%, Ca 0.5-1.4%, and the balance is Magnesium and impurities; the as-cast magnesium alloy is subjected to primary heat treatment at a temperature of 420-440°C for 4-6 hours and cooled with the furnace; 2) secondary heat treatment is performed at a temperature of 390-410°C , the time is 8-10 hours, water cooling; 3) carry out three-stage heat treatment, the temperature of the three-stage heat treatment is 200-220 ℃, the time is 12-15 hours, air-cooling, to obtain. The heat treatment method provided by the invention optimizes the microstructure of the magnesium alloy through two-stage solid solution treatment, thereby improving the final mechanical properties of the magnesium alloy.

Description

A kind of preparation method of multi-component heat-resistant magnesium alloy and multi-component heat-resistant magnesium alloy

technical field

The invention belongs to the technical field of metallurgy and heat treatment, and in particular relates to a preparation method of a multi-element heat-resistant magnesium alloy and the multi-element heat-resistant magnesium alloy.

Background technique

As the lightest metal structural material, magnesium alloy has high specific strength and specific stiffness, excellent casting performance and machining performance, and has a very wide application prospect. In recent years, magnesium alloys have been increasingly used in automobiles. The use of magnesium alloys in automobiles can reduce weight and reduce exhaust emissions. Therefore, the research and development of magnesium alloys is of great significance for saving energy and suppressing environmental pollution.

Mg-Al-Zn series magnesium alloys (such as AZ31, AZ61, AZ91, etc.) are currently the most widely used magnesium alloy series in industry. This series of magnesium alloys has the advantages of good strength, plasticity, corrosion resistance and low cost. But it has its own insurmountable shortcomings: First, the Mg ₁₇ Al ₁₂ phase in the as-cast Mg-Al-Zn series magnesium alloy precipitates in the form of a dissociated eutectic network along the grain boundaries, and these coarse Mg ₁₇ Al ₁₂ phases The presence of is detrimental to the mechanical properties of the alloy. In addition, when the working temperature is higher than 120 °C, the main strengthening phase Mg ₁₇ Al ₁₂ in this series of alloys will be coarsened or softened, so that its strengthening effect on the matrix is greatly reduced, thereby reducing the high temperature performance of this series of magnesium alloys. The lower mechanical properties limit the application range of Mg-Al-Zn series magnesium alloys.

Adding alloying elements is one of the effective ways to improve the properties of magnesium alloys. There are three main types of alloying elements added to Mg-Al-Zn series magnesium alloys: ① Alkaline earth elements such as Ca and Sr; ② Rare earth elements RE; ③ Group IV and V elements, such as Si, Sn, Sb, Bi, etc. While these alloying elements provide new properties for magnesium alloys, they also put forward higher requirements for the heat treatment methods of magnesium alloys. Due to the particularity of Mg-Al-Zn series magnesium alloys, conventional heat treatment processes are difficult to effectively improve the segregation of magnesium alloys and the uniformity of precipitated phases, and structural defects such as shrinkage porosity and pores are prone to appear in the alloy structure, which in turn affects the quality of magnesium alloys. mechanical properties.

Patent CN103469039A discloses a magnesium-aluminum-zinc deformed magnesium alloy containing calcium and rare earth samarium, its mass percentage content is Al 5.3-6.0%, Zn 0.7-1.0%, Ca 0.4-0.5%, Sm 0.2-1.5% , the balance is Mg; through the melting of raw materials and quick cooling in salt bath, the obtained alloy ingot is homogenized and annealed at 400°C and air-cooled to room temperature, and hot-extruded at 360°C with an extrusion ratio of 25:1 to obtain calcium and rare earth samarium magnesium-aluminum-zinc wrought magnesium alloy. After the magnesium alloy is deformed by hot extrusion, the alloy phase is refined, and the tensile strength, yield strength and elongation of the material are all improved. However, the hot extrusion process requires specific extrusion equipment, and has limitations on the size and shape of the material; at the same time, the hot extrusion process is often accompanied by heating defects such as serious oxidation and decarburization, which affects the size of the extrusion Precision and surface roughness; the above characteristics affect the large-scale application of this process in industrial production.

The development of a heat treatment method with simple equipment, low cost, safety, reliability, and convenient operation plays an important role for Mg-Al-Zn series magnesium alloys. Heat treatment can effectively reduce the internal stress of the casting, eliminate segregation in the alloy structure, dissolve the non-equilibrium phase in the matrix, and homogenize the alloy composition. When the solid solubility of alloy elements changes with temperature, the solid solution treatment can significantly Improve the performance of magnesium alloy. The heat treatment of Mg-Al-Zn cast magnesium alloys generally includes two steps of solution treatment and aging treatment, among which solution treatment is the basis and key of subsequent aging treatment of the alloy. How to obtain a good solution effect through process control is very important for Mg- The heat treatment strengthening of Al-Zn alloys is particularly critical. Solution treatment needs to control the treatment temperature and treatment time well. If the temperature is too high or the heating time is too long, the structure will grow and coarsen, wasting heat; if the temperature is too low or the heating time is too short, the alloying elements will not dissolve enough , affecting its mechanical properties. Therefore, how to optimize the heat treatment process of magnesium alloys and research and development of new heat treatment methods for magnesium alloys is particularly important for maximizing the strengthening effect of cast Mg-Al-Zn alloys.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a multi-component heat-resistant magnesium alloy, which solves the technical problem of poor mechanical properties of the magnesium alloy due to segregation and poor uniformity of precipitated phase distribution in the prior art.

The second object of the present invention is to provide a multi-component heat-resistant magnesium alloy obtained by the above preparation method.

In order to achieve the above object, the technical solution adopted in the present invention is:

A method for preparing a multi-component heat-resistant magnesium alloy, comprising the following steps:

1) The as-cast magnesium alloy is subjected to primary heat treatment, the temperature of the primary heat treatment is 420-440°C, the heat treatment time is 4-6h, and cooled; the as-cast magnesium alloy is composed of the following components in mass percentage: Al 7.5 ～8.5%, Zn 0.8～1.2%, RE 1.2～2.4%, Ca 0.5～1.4%, the balance is magnesium and impurities;

2) performing secondary heat treatment on the magnesium alloy cooled in step 1), the temperature of the secondary heat treatment is 390-410°C, the heat treatment time is 8-10 hours, and then cooled;

3) The magnesium alloy cooled in step 2) is subjected to tertiary heat treatment, the temperature of the tertiary heat treatment is 200-220° C., the heat treatment time is 12-15 hours, and cooling is obtained.

In step 1), RE is any one of Gd, Y, Nd, and Sm.

The impurities are Fe, Cu and Ni, and the total amount is less than 0.2wt%.

In the preparation method of the above multi-component heat-resistant magnesium alloy, the primary heat treatment and the secondary heat treatment are solid solution treatment steps, and the tertiary heat treatment is an aging treatment step. Solution treatment heats the alloy to a high-temperature single-phase region and maintains it at a constant temperature, so that the excess phase is fully dissolved in the solid solution, and then a supersaturated solid solution is obtained by cooling; the heat treatment method provided by the invention avoids the alloy Insufficient dissolution of elements or the growth and coarsening of the alloy structure make the alloy precipitates evenly distributed and the alloy structure is optimized, thereby improving the final mechanical properties of the magnesium alloy. Among the alloy components, Ca has good grain refinement and anti-oxidation effects in magnesium alloys, and can refine the matrix structure of magnesium alloys to improve the strength and plasticity of magnesium alloys; a small amount of Ca in Mg-Al series magnesium alloys will solidify Dissolving into the Mg ₁₇ Al ₁₂ phase improves its thermal stability, and Ca easily forms a high-temperature stable Al-Ca phase with Al to improve the high-temperature performance of the alloy. The addition of rare earth element RE to magnesium alloy has solid solution strengthening and second phase strengthening effects, thereby improving the mechanical properties of the alloy. In addition, the heat treatment method provided by the invention has the advantages of simple equipment, low cost, safety and reliability, and convenient operation, and is suitable for large-scale industrial production applications.

Step 1) The primary heat treatment can be carried out in various heat treatment furnaces (such as box-type resistance furnaces, etc.). The preferred cooling method for the primary heat treatment is cooling with the furnace. This treatment can cause solid-state diffusion of elements in the alloy and reduce intragranular segregation And dendrite segregation, which makes the composition uniform, and slow cooling with the furnace can increase the diffusion of alloying elements, reduce casting defects, and optimize the microstructure of the alloy.

Step 2) The cooling method of the secondary heat treatment is preferably hot water cooling; the temperature of the hot water used is 70-90°C, which can obtain a supersaturated solid solution of the magnesium alloy, and hot water quenching can reduce the hot cracking tendency of the alloy and improve the integrity of the structure sex.

Step 3) The cooling method of the tertiary heat treatment is preferably air cooling, and this process is artificial aging treatment, and the precipitation of the dispersed phase from the supersaturated solid solution can play a role of dispersion strengthening.

Step 1) A variety of existing technologies can be used to obtain the cast magnesium alloy from raw materials. Step 1) The as-cast magnesium alloy is preferably prepared by the following method: under a protective atmosphere, the raw materials are melted according to the ratio, and then cast to obtain the as-cast magnesium alloy. The protective atmosphere is a mixed gas of CO ₂ and SF ₆ . The casting temperature is 710-730°C.

The present invention also provides a multi-element heat-resistant magnesium alloy obtained by the above-mentioned preparation method of the multi-element heat-resistant magnesium alloy. In the multi-component heat-resistant magnesium alloy provided by the invention, each phase in the alloy is evenly distributed, the strength and heat resistance of the alloy are significantly improved, the tensile strength at room temperature reaches 273Mpa, and the yield strength reaches 204MPa; at a working temperature of 200°C, the tensile strength and The yield strength reaches 196Mpa and 141Mpa respectively; the mechanical properties are excellent and have broad application space.

Description of drawings

Fig. 1 is the temperature-time schematic diagram of traditional magnesium alloy heat treatment method;

Fig. 2 is the temperature-time relation schematic diagram of the preparation method of multi-element heat-resistant magnesium alloy of the present invention;

3 is the metallographic structure diagram of Comparative Example 1 and Example 1 of the present invention, wherein (a) is the metallographic structure diagram of Comparative Example 1, and (b) is the metallographic structure diagram of Example 1.

detailed description

The present invention will be further described below in conjunction with specific examples.

Example 1

The preparation method of the multi-element heat-resistant magnesium alloy of the present embodiment comprises the following steps:

1) Put the corundum crucible with raw materials into an intermediate frequency induction furnace, and melt under the protection of CO ₂ +SF ₆ mixed gas. After the raw materials are melted, when the temperature of the magnesium alloy melt is raised to 720°C, it is cast into a steel mold , to obtain the cast magnesium alloy; the mass percent of the cast magnesium alloy consists of: Al 8.0%, Zn 1%, Y 1.7%, Ca 0.8%, and the balance is Mg and impurities;

2) The as-cast magnesium alloy obtained in step 1) is subjected to primary heat treatment in a box-type resistance furnace, the primary heat treatment temperature is 430° C., the primary heat treatment time is 4 hours, and the furnace is cooled;

3) putting the cooled magnesium alloy in step 2) into a heat treatment furnace for secondary heat treatment, the secondary heat treatment temperature is 400°C, the secondary heat treatment time is 8 hours, and cooled with 80°C hot water;

4) Put the cooled magnesium alloy in step 3) into a heat treatment furnace for three-stage heat treatment, the temperature of the three-stage heat treatment is 210° C., the time of the three-stage heat treatment is 14 hours, and air cooling is obtained.

The mass percentage composition of the multi-component heat-resistant magnesium alloy obtained by the preparation method of this embodiment is 8% Al, 1% Zn, 1.7% Y, 0.8% Ca, and the balance is Mg and impurities.

Comparative example 1

The composition of the raw material of the multi-element heat-resistant magnesium alloy of comparative example 1 is the same as that of Example 1; the preparation process of the as-cast magnesium alloy is the same as that of Example 1. The preparation method of comparative example 1 multi-element heat-resistant magnesium alloy comprises the following steps:

1) The as-cast magnesium alloy is subjected to solution treatment in a box-type resistance furnace, the solution treatment temperature is 420°C, the solution treatment time is 12 hours, and cooled with 80°C hot water;

2) Put the cooled magnesium alloy in step 1) into a heat treatment furnace for aging treatment, the aging treatment temperature is 210° C., the aging treatment time is 14 hours, air-cooled, and the product is obtained.

Example 2

The preparation method of the multi-element heat-resistant magnesium alloy of the present embodiment comprises the following steps:

1) Put the corundum crucible with raw materials into an intermediate frequency induction furnace, and melt under the protection of CO ₂ +SF ₆ mixed gas. After the raw materials are melted, when the temperature of the magnesium alloy melt is raised to 710°C, it is cast into a steel mold , to obtain the cast magnesium alloy; the mass percent of the cast magnesium alloy consists of: Al 7.6%, Zn 1.2%, Gd 2.0%, Ca 0.6%, and the balance is Mg and impurities;

2) The as-cast magnesium alloy obtained in step 1) is subjected to primary heat treatment in a box-type resistance furnace, the primary heat treatment temperature is 420° C., the primary heat treatment time is 5 hours, and the furnace is cooled;

3) Put the cooled magnesium alloy in step 2) into a heat treatment furnace for secondary heat treatment, the secondary heat treatment temperature is 410°C, the secondary heat treatment time is 9 hours, and 80°C hot water cooling;

4) Put the cooled magnesium alloy in step 3) into a heat treatment furnace for three-stage heat treatment, the temperature of the three-stage heat treatment is 200° C., the time of the three-stage heat treatment is 13 hours, and air cooling is obtained.

The mass percentage composition of the multi-component heat-resistant magnesium alloy obtained by the preparation method of this embodiment is 8% Al, 1% Zn, 2.0% Gd, 0.6% Ca, and the balance is Mg and impurities.

Comparative example 2

Comparative Example 2 The composition of the multi-component heat-resistant magnesium alloy raw material is the same as that of Example 2; the preparation process of the as-cast magnesium alloy is the same as that of Example 2. The preparation method of comparative example 2 multi-element heat-resistant magnesium alloy comprises the following steps:

1) The as-cast magnesium alloy is subjected to solution treatment in a box-type resistance furnace, the solution treatment temperature is 415°C, the solution treatment time is 14 hours, and cooled with 80°C hot water;

2) Put the cooled magnesium alloy in step 1) into a heat treatment furnace for aging treatment, the aging treatment temperature is 200° C., the aging treatment time is 13 hours, and air-cooled to obtain a multi-element heat-resistant magnesium alloy.

Example 3

The preparation method of the multi-element heat-resistant magnesium alloy of the present embodiment comprises the following steps:

1) Put the corundum crucible with raw materials into an intermediate frequency induction furnace, and melt under the protection of CO ₂ +SF ₆ mixed gas. After the raw materials are melted, when the temperature of the magnesium alloy melt is raised to 730°C, it is cast into a steel mold , to obtain the cast magnesium alloy; the mass percent of the cast magnesium alloy consists of: Al 7.8%, Zn 0.9%, Nd 1.9%, Ca 1.0%, and the balance is Mg and impurities;

2) The as-cast magnesium alloy obtained in step 1) is subjected to primary heat treatment in a box-type resistance furnace, the primary heat treatment temperature is 430° C., the primary heat treatment time is 4 hours, and the furnace is cooled;

3) Put the cooled magnesium alloy in step 2) into a heat treatment furnace for secondary heat treatment, the secondary heat treatment temperature is 390°C, the secondary heat treatment time is 10 hours, and 90°C hot water cooling;

4) Put the cooled magnesium alloy in step 3) into a heat treatment furnace for three-stage heat treatment, the temperature of the three-stage heat treatment is 200° C., the time of the three-stage heat treatment is 15 hours, and air cooling is obtained.

The mass percentage composition of the multi-component heat-resistant magnesium alloy obtained by the preparation method of this embodiment is 8% Al, 1% Zn, 1.9% Nd, 1.0% Ca, and the balance is Mg and impurities.

Comparative example 3

The composition of the raw material of the multi-element heat-resistant magnesium alloy in comparative example 3 is the same as that of Example 3; the preparation process of the as-cast magnesium alloy is the same as that of Example 3. The preparation method of comparative example 3 multi-element heat-resistant magnesium alloy comprises the following steps:

1) The as-cast magnesium alloy is subjected to solution treatment in a box-type resistance furnace, the solution treatment temperature is 425 ° C, the solution treatment time is 11 hours, and 90 ° C hot water cooling;

2) Put the magnesium alloy obtained in step 1) into a heat treatment furnace for aging treatment, the aging treatment temperature is 200° C., the aging treatment time is 15 hours, and air-cooled to obtain a multi-element heat-resistant magnesium alloy.

Example 4

The preparation method of the multi-element heat-resistant magnesium alloy of the present embodiment comprises the following steps:

1) Put the corundum crucible with raw materials into an intermediate frequency induction furnace, and melt under the protection of CO ₂ +SF ₆ mixed gas. After the raw materials are melted, when the temperature of the magnesium alloy melt is raised to 710°C, it is cast into a steel mold , to obtain the as-cast magnesium alloy; the mass percentage of the as-cast magnesium alloy consists of: Al 8.3%, Zn 0.8%, Sm 1.3%, Ca 1.2%, and the balance is Mg and impurities;

2) The as-cast magnesium alloy obtained in step 1) is subjected to primary heat treatment in a box-type resistance furnace, the primary heat treatment temperature is 430° C., the primary heat treatment time is 6 hours, and the furnace is cooled;

3) Put the cooled magnesium alloy in step 2) into a heat treatment furnace for secondary heat treatment, the secondary heat treatment temperature is 410°C, the secondary heat treatment time is 8 hours, and 80°C hot water cooling;

4) Put the cooled magnesium alloy in step 3) into a heat treatment furnace for three-stage heat treatment, the temperature of the three-stage heat treatment is 200° C., the time of the three-stage heat treatment is 15 hours, and air cooling is obtained.

The mass percent composition of the multi-component heat-resistant magnesium alloy obtained by the preparation method of this embodiment is 8% Al, 1% Zn, 1.3% Sm, 1.2% Ca, and the balance is Mg and impurities.

Comparative example 4

The composition of the raw material of the multi-element heat-resistant magnesium alloy in Comparative Example 4 is the same as that of Example 4; the preparation process of the as-cast magnesium alloy is the same as that of Example 4. The preparation method of comparative example 4 multi-element heat-resistant magnesium alloy comprises the following steps:

1) The as-cast magnesium alloy is subjected to solution treatment in a box-type resistance furnace, the solution treatment temperature is 430 ° C, the solution treatment time is 10 hours, and 80 ° C hot water cooling;

2) Put the cooled magnesium alloy in step 1) into a heat treatment furnace for aging treatment, the aging treatment temperature is 200° C., the aging treatment time is 15 hours, air cooling to obtain a multi-element heat-resistant magnesium alloy.

Example 5

The preparation method of the multi-element heat-resistant magnesium alloy of the present embodiment comprises the following steps:

1) Put the corundum crucible with raw materials into an intermediate frequency induction furnace, and melt under the protection of CO ₂ +SF ₆ mixed gas. After the raw materials are melted, when the temperature of the magnesium alloy melt is raised to 730°C, it is cast into a steel mold , to obtain the cast magnesium alloy; the mass percent of the cast magnesium alloy consists of: Al 8.4%, Zn 1.1%, Gd 2.3%, Ca 1.4%, and the balance is Mg and impurities;

2) Carrying out the primary heat treatment of the as-cast magnesium alloy obtained in step 1) in a box-type resistance furnace, the primary heat treatment temperature is 440° C., the primary heat treatment time is 5 hours, and is cooled with the furnace;

3) Put the cooled magnesium alloy in step 2) into a heat treatment furnace for secondary heat treatment, the secondary heat treatment temperature is 390°C, the secondary heat treatment time is 10 hours, and 70°C hot water cooling;

4) Put the magnesium alloy cooled in step 3) into a heat treatment furnace for three-stage heat treatment, the temperature of the three-stage heat treatment is 220° C., the time of the three-stage heat treatment is 14 hours, and air cooling is obtained.

The mass percentage composition of the multi-element heat-resistant magnesium alloy obtained by the preparation method of this embodiment is 8% Al, 1% Zn, 2.3% Gd, 1.4% Ca, and the balance is Mg and impurities.

Comparative example 5

Comparative Example 5 The composition of the multi-component heat-resistant magnesium alloy raw material is the same as that of Example 5; the preparation process of the as-cast magnesium alloy is the same as that of Example 5. The preparation method of comparative example 5 multi-element heat-resistant magnesium alloy comprises the following steps:

1) The as-cast magnesium alloy is subjected to solution treatment in a box-type resistance furnace, the solution treatment temperature is 410 ° C, the solution treatment time is 15 hours, and 70 ° C hot water cooling;

2) Put the cooled magnesium alloy in step 1) into a heat treatment furnace for aging treatment, the aging treatment temperature is 220° C., the aging treatment time is 14 hours, and air-cooled to obtain a multi-element heat-resistant magnesium alloy.

Test case

The tensile strength and yield strength of the multi-element heat-resistant magnesium alloys of various examples and comparative examples were tested at room temperature and working temperature (200° C.), and the test results are shown in Table 1. It can be seen from Table 1 that the multi-component heat-resistant magnesium alloy obtained by the heat treatment method of the present invention has high tensile strength and yield strength at room temperature and 200° C., and has excellent mechanical properties.

The mechanical property detection result of the multi-element heat-resistant magnesium alloy of table 1 each embodiment and comparative example

(Note: (furnace) means that the cooling method is furnace cooling; (water) means that the cooling method is hot water cooling, and the water temperature is 70-90°C; (empty) means that the cooling method is air cooling.)

Traditional magnesium alloy heat treatment method temperature-time schematic diagram as shown in Figure 1, after a solid solution treatment, water cooling; Then aging treatment, air cooling, obtain magnesium alloy; the temperature of the preparation method of multi-element heat-resistant magnesium alloy of the present invention- The schematic diagram of the time relationship is shown in Figure 2. After the second solution treatment, the cooling methods of the second solution treatment are furnace cooling and water cooling respectively; then aging treatment and air cooling are performed to obtain a multi-component heat-resistant magnesium alloy. By optimizing the heat treatment process, the metallographic structure of the magnesium alloy can be optimized, so that the strength and heat resistance of the alloy can be significantly improved.

3 is the metallographic structure diagram of Comparative Example 1 and Example 1 of the present invention, wherein (a) is the metallographic structure diagram of Comparative Example 1, and (b) is the metallographic structure diagram of Example 1. Compared with the metallographic structure of the comparative example, the multi-element heat-resistant magnesium alloy obtained in Example 1 has less intragranular segregation and dendrite segregation, a high degree of homogeneity of alloy components, and the dispersed phase grains are refined and evenly distributed, which is beneficial to Reduce the generation of defects, maintain the integrity of the organization, and improve the macroscopic mechanical properties.

Claims (8)

1. a kind of preparation method of multicomponent heat-resistant magnesium alloy, it is characterised in that comprise the following steps：

1) as-cast magnesium alloy is carried out into one-level heat treatment, the one-level heat treatment temperature is 420~440 DEG C, and heat treatment time is 4 ~6h, cooling；The as-cast magnesium alloy is made up of the component of following mass percent：Al 7.5~8.5%, Zn 0.8~ 1.2%, RE 1.2~2.4%, Ca 0.5~1.4%, balance of magnesium and impurity；Wherein, RE is any one in Gd, Y, Nd, Sm Kind；

2) by step 1) cooling after magnesium alloy carry out two grades heat treatment, two grades of heat treatment temperatures be 390~410 DEG C, heat Process time is 8~10 hours, cooling；

3) by step 2) magnesium alloy after cooling carries out three-level heat treatment, and the three-level heat treatment temperature is 200~220 DEG C, heat Process time is 12~15 hours, and cooling is obtained final product.

2. the preparation method of multicomponent heat-resistant magnesium alloy as claimed in claim 1, it is characterised in that step 1) in, it is described to be cooled to Furnace cooling.

3. the preparation method of multicomponent heat-resistant magnesium alloy as claimed in claim 1, it is characterised in that step 2) in, it is described to be cooled to Hot water is cooled down；Hot water temperature used is 70~90 DEG C.

4. the preparation method of multicomponent heat-resistant magnesium alloy as claimed in claim 1, it is characterised in that step 3) in, it is described to be cooled to Air cooling.

5. as any one of Claims 1 to 4 multicomponent heat-resistant magnesium alloy preparation method, it is characterised in that step 1) institute As-cast magnesium alloy is stated to be prepared by following methods：Under protective atmosphere, raw material is carried out into melting, casting by proportioning, obtain final product casting State magnesium alloy.

6. the preparation method of multicomponent heat-resistant magnesium alloy as claimed in claim 5, it is characterised in that the protective atmosphere is CO₂With SF₆Mixed gas.

7. the preparation method of multicomponent heat-resistant magnesium alloy as claimed in claim 5, it is characterised in that the temperature of the casting is 710 ~730 DEG C.

8. the multicomponent heat-resistant magnesium alloy obtained by a kind of preparation method as described in claim 1.