Mg-Nd-Gd-Sb heat-resistant magnesium alloy and preparation method thereof

Abstract

The invention relates to the technical field of magnesium alloy smelting, in particular to a Mg-Nd-Gd-Sb heat-resistant magnesium alloy and a preparation method thereof. According to the high-strength heat-resistant magnesium alloy containing rare earth Nd and Gd and the element Sb, on the basis that precipitation strengthening of rare earth intermetallic compounds containing Nd and Gd is used as a main strengthening mechanism, the Sb element is introduced to form a Mg3Sb2 high-temperature strengthening phase with high stability, on the premise that the total amount of rare earth is not greatly increased, the room-temperature and high-temperature strength performance indexes are improved to different degrees, and the high-strength heat-resistant magnesium alloy containing rare earth Nd and Gd is obtained. And good formability is maintained, and engineering application is easy to realize. The high-strength heat-resistant magnesium alloy containing the rare earth Nd, the rare earth Gd and the element Sb is excellent in high-temperature mechanical property, the tensile strength, the yield strength and the ductility of a heat treatment state material after casting at the temperature of 300 DEG C reach 230-245 MPa, 145-150 MPa and 5-7% correspondingly, and the requirements for the mechanical property of a light structural material in a high-temperature environment in the current fields of aerospace, rail transit and the like can be met.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium alloy smelting, in particular to a Mg-Nd-Gd-Sb heat-resistant magnesium alloy and a preparation method thereof. Background Art

[0002] As the lightest commercial metal engineering structural material, magnesium alloy is known as the "green structural material" of the 21st century because of its light weight, high specific strength and stiffness, strong damping, vibration and noise reduction capabilities, superior liquid forming performance and easy recycling. Casting is the most widely used forming method for magnesium alloys, and cast magnesium alloy materials are also the fastest industrialized magnesium alloy materials. However, due to the poor high-temperature performance of existing cast magnesium alloys and the long-term working temperature cannot exceed 120°C, it cannot be used to manufacture structural parts with high requirements for high-temperature performance, which greatly hinders the further promotion and application of magnesium alloys.

[0003] Domestic and foreign countries have paid extensive attention and high attention to the research and development of heat-resistant cast magnesium alloys with high-temperature performance, and have developed new heat-resistant cast magnesium alloys of Mg-Nd, Mg-Gd, and Mg-Y series with high performance at 200°C or even 250°C. Among these heat-resistant magnesium alloys that have been trial-produced and studied, WE43 and EV31 cast magnesium alloys are considered to be a promising new generation of high-temperature magnesium alloy materials due to their advantages in high-temperature performance and low cost.

[0004] With the development of the industry, the demand for high temperature resistance of casting materials has been continuously increased to above 300°C. The high temperature performance of traditional WE43 and EV31 cast magnesium alloys is difficult to exceed 220MPa and can no longer meet the requirements. However, by significantly increasing the expensive heavy rare earths such as Gd and Nd to improve the high temperature resistance, the cost will inevitably be greatly increased, while only obtaining a performance benefit of about 20MPa, which is difficult to achieve industrial application. For example: CN114645170B (a cast magnesium rare earth alloy that can be rapidly solution treated at high temperature and a preparation method thereof) obtains a good improvement in room temperature mechanical properties by adding La elements, but high temperature performance, especially performance above 300°C, is not involved. CN114058891A (a method for adding zirconium elements in the smelting of zirconium-containing rare earth cast magnesium alloys) achieves a grain refinement effect through conventional rare earth element adjustment, but also does not involve performance improvement.

[0005] Therefore, it is urgent to develop a low-cost cast magnesium alloy material with excellent high-temperature resistance. Summary of the invention

[0006] In order to solve the above technical problems existing in the prior art, the present invention provides a Mg-Nd-Gd-Sb heat-resistant magnesium alloy and a preparation method thereof, which are specifically achieved through the following technical solutions.

[0007] A Mg-Nd-Gd-Sb heat-resistant magnesium alloy, the components of the alloy and their mass percentages are as follows:

[0008] 2.5-3.5wt.% Nd;

[0009] 2-4 wt.% Gd;

[0010] 0.5-1 wt.% Sb;

[0011] 0.5~1wt.%Zr;

[0012] Fe≤0.002%, the balance is Mg.

[0013] The preparation method of the Mg-Nd-Gd-Sb heat-resistant magnesium alloy comprises the following steps:

[0014] (1) Composition determination: Mg-Nd-Gd-S heat-resistant magnesium alloy, the components of the alloy and their mass percentages are as follows:

[0015] 2.5~3.5wt.% Nd,

[0016] 2~4wt.% Gd,

[0017] 0.5~1wt.% Sb,

[0018] 0.5~1wt.%Zr,

[0019] Fe≤0.002%, the balance is Mg.

[0020] (2) Batching: Batching according to the composition of the Mg-Nd-Gd-Sb heat-resistant magnesium alloy, and preheating the raw materials;

[0021] (3) Melting: Under gas protection, when the temperature of the melting furnace reaches 200-250° C., preheated pure Mg, pure Sb, Mg-30wt.% Nd and Mg-30wt.% Gd master alloys are added and melted. After melting, the temperature is raised to 780-800° C., and then the preheated Mg-30wt.% Zr master alloy is added. After the master alloys are melted, the alloy melt is stirred to keep the temperature, and the scum on the surface of the alloy liquid is removed. The temperature is lowered to 760-780° C. and stirred with RJ-5 refining agent for 5-10 minutes. The scum on the alloy liquid is removed. After the treatment is completed, the temperature is lowered to 720-740° C. and allowed to stand for 10-15 minutes, and then casting is performed;

[0022] (4) Solution treatment: Heat the magnesium alloy casting to 500-520°C, keep it warm for 12-14 hours, and then quickly put it into water to cool it down rapidly;

[0023] (5) Aging treatment: The casting obtained in step (3) is kept at a temperature of 200 to 210° C. for 16 to 20 hours, and then taken out and naturally cooled to room temperature in an atmospheric environment.

[0024] Furthermore, the Mg and Sb are added in the form of pure Mg and pure Sb.

[0025] Furthermore, the Nd, Gd and Zr are added in the form of Mg-30wt.%Nd, Mg-30wt.%Gd and Mg-30wt.%Zr master alloys, respectively.

[0026] Furthermore, the preheating in step (2) is specifically preheating at 200° C. for 1 hour.

[0027] Furthermore, the gas in step (3) is specifically a mixed protective atmosphere of CO2 and SF6 (100:1).

[0028] Furthermore, in the step (3), after the intermediate alloy is melted, the alloy melt is stirred and kept warm, specifically for 12-20 minutes.

[0029] Furthermore, the rapid cooling by placing in water in step (4) is rapid cooling by placing in water at room temperature.

[0030] Compared with the prior art, the technical effects created by the present invention are embodied in:

[0031] (1) The present invention obtains a high-strength and heat-resistant magnesium alloy containing rare earth Nd, Gd and element Sb. On the basis of precipitation strengthening of rare earth intermetallic compounds containing Nd and Gd as the main strengthening mechanism, the Sb element is introduced to form a highly stable Mg3Sb2 high-temperature strengthening phase. Without a large increase in the total amount of rare earth, the room temperature and high temperature strength performance indicators are improved to varying degrees, and good formability is retained, which is easy to realize engineering applications.

[0032] (2) The room temperature mechanical properties of the high-strength heat-resistant magnesium alloy containing rare earth Nd, Gd and element Sb of the present invention are significantly improved: the room temperature tensile strength, yield strength and elongation of the material after casting heat treatment reach 285-310 MPa, 170-180 MPa and 4-6%, respectively.

[0033] (3) The high-strength and heat-resistant magnesium alloy containing rare earth Nd, Gd and element Sb of the present invention has excellent high-temperature mechanical properties: the tensile strength, yield strength and elongation of the material after casting heat treatment at 300°C are respectively 230-245MPa, 145-150MPa and 5-7%, which can meet the current requirements of aerospace, rail transportation and other fields for the mechanical properties of lightweight structural materials in high-temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the metallographic diagram of the magnesium alloy in the heat-treated state in Example 1.

[0035] Figure 2 This is the metallographic diagram of the cast magnesium alloy in Example 1. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further defined below in conjunction with specific implementation methods, but the scope of protection required is not limited to the description.

[0037] Example 1

[0038] A Mg-Nd-Gd-Sb heat-resistant magnesium alloy is prepared by the following steps:

[0039] (1) Composition determination: Mg-Nd-Gd-Sb heat-resistant magnesium alloy, the components of the alloy and their mass percentages are as follows:

[0040] 2.9wt.%Nd,

[0041] 3wt.%Gd,

[0042] 0.8wt.% Sb,

[0043] 0.8wt.% Zr,

[0044] Fe=0.0015%, the balance is Mg.

[0045] (2) Material preparation: 10 kg of materials are prepared, and each element is prepared according to the composition ratio of the Mg-Nd-Gd-Sb heat-resistant magnesium alloy. The Mg and Sb are added in the form of pure Mg and pure Sb, and the Nd, Gd and Zr are added in the form of Mg-30wt.%Nd, Mg-30wt.%Gd and Mg-30wt.%Zr master alloys, respectively. Each raw material is preheated at 200°C for 1 hour;

[0046] (3) Melting: in a mixed protective atmosphere of CO2 and SF6 (100:1), when the temperature of the melting furnace reaches 200-250°C, preheated pure Mg, pure Sb, Mg-30wt.%Nd and Mg-30wt.%Gd master alloys are added and melted, and the temperature is raised to 780-800°C after melting, and then the preheated Mg-30wt.%Zr master alloy is added. After the master alloys are melted, the alloy melt is stirred and kept warm for 15 minutes, and the scum on the surface of the alloy liquid is removed. The alloy liquid is cooled to 760-780°C and stirred for 7 minutes with RJ-5 refining agent, and the scum on the alloy liquid is removed. After the treatment is completed, the temperature is cooled to 720-740°C and left to stand for 12 minutes, and then casting is carried out;

[0047] (4) Solution treatment: Heat the magnesium alloy casting to 500-520°C, keep it warm for 13 hours, and then quickly place it in room temperature water to cool it down rapidly;

[0048] (5) Aging treatment: The casting obtained in step (3) is kept at a temperature of 200-210° C. for 18 h, then taken out and naturally cooled to room temperature in an atmospheric environment.

[0049] The Mg-Nd-Gd-Sb high-strength heat-resistant magnesium alloy obtained by the above method has precipitation strengthening containing rare earth metal intermetallic compounds as the main strengthening mechanism, which significantly improves the heat treatment aging hardening effect and heat resistance of the material of the present invention. The material has excellent room temperature and high temperature mechanical properties, and the performance values ​​are as follows:

[0050] Table 1 Performance values ​​of commercial heat-resistant magnesium alloys of the present invention and comparison

[0051]

[0052] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the technical solution of the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by ordinary technicians in this field should be considered as the protection scope of the present invention.

Claims

1. A Mg-Nd-Gd-Sb heat-resistant magnesium alloy, characterized in that: The alloy components and their mass percentages are as follows: 2.5-3.5wt.% Nd; 2-4 wt.% Gd; 0.5-1 wt.% Sb; 0.5~1wt.%Zr; Fe≤0.002%, the balance is Mg.

2. A method for preparing the Mg-Nd-Gd-Sb heat-resistant magnesium alloy according to claim 1, characterized in that: The following steps are involved: (1) Composition determination: Mg-Nd-Gd-S heat-resistant magnesium alloy, the components of the alloy and their mass percentages are as follows: 2.5~3.5wt.% Nd, 2~4wt.% Gd, 0.5~1wt.% Sb, 0.5~1wt.%Zr, Fe≤0.002%, the balance is Mg. (2) Batching: Batching the ingredients according to the composition of the Mg-Nd-Gd-Sb heat-resistant magnesium alloy, and preheating the raw materials; (3) Melting: Under gas protection, when the temperature of the melting furnace reaches 200-250° C., preheated pure Mg, pure Sb, Mg-30wt.% Nd and Mg-30wt.% Gd master alloys are added and melted. After melting, the temperature is raised to 780-800° C., and then the preheated Mg-30wt.% Zr master alloy is added. After the master alloys are melted, the alloy melt is stirred to keep the temperature, and the scum on the surface of the alloy liquid is removed. The temperature is lowered to 760-780° C. and stirred for 5-10 minutes with RJ-5 refining agent. The scum on the alloy liquid is removed. After the treatment is completed, the temperature is lowered to 720-740° C. and allowed to stand for 10-15 minutes, and then casting is performed; (4) Solution treatment: Heat the magnesium alloy casting to 500-520°C, keep it warm for 12-14 hours, and then quickly put it into water to cool it down rapidly; (5) Aging treatment: The casting obtained in step (3) is kept at a temperature of 200 to 210° C. for 16 to 20 hours, and then taken out and naturally cooled to room temperature in an atmospheric environment.

3. The Mg-Nd-Gd-Sb heat-resistant magnesium alloy and the preparation method thereof according to claim 1, characterized in that: The Mg and Sb are added in the form of pure Mg and pure Sb.

4. The Mg-Nd-Gd-Sb heat-resistant magnesium alloy and the preparation method thereof according to claim 1, characterized in that: The Nd, Gd and Zr are added in the form of Mg-30wt.%Nd, Mg-30wt.%Gd and Mg-30wt.%Zr master alloys, respectively.

5. The Mg-Nd-Gd-Sb heat-resistant magnesium alloy and the preparation method thereof according to claim 1, characterized in that: The preheating in step (2) is specifically preheating at 200° C. for 1 hour.

6. The Mg-Nd-Gd-Sb heat-resistant magnesium alloy and the preparation method thereof according to claim 1, characterized in that: The gas protection in step (3) is specifically a mixed protective atmosphere of CO2 and SF6 (100:1).

7. The Mg-Nd-Gd-Sb heat-resistant magnesium alloy and the preparation method thereof according to claim 1, characterized in that: In the step (3), after the intermediate alloy is melted, the alloy melt is stirred and kept warm, specifically for 12-20 minutes.

8. The Mg-Nd-Gd-Sb heat-resistant magnesium alloy and the preparation method thereof according to claim 1, characterized in that: The rapid cooling in the step (4) is rapid cooling in water by placing in room temperature water.

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