High-toughness high-modulus wrought magnesium alloy and method of making same

Abstract

A high-strength, high-toughness, and high-modulus wrought magnesium alloy and its preparation method are disclosed, relating to the field of magnesium alloy technology. The high-strength, high-toughness, and high-modulus wrought magnesium alloy, by mass fraction, comprises: 11.0~13.0% Gd, 0.8~1.2% Zn, 0.3~0.7% Zr, 0.3~0.7% Ag, 0.3~0.7% Ru, and 3.5~4.5%... The alloy is composed of Al, with the balance being Mg and unavoidable impurities. Its preparation method includes the following steps: S1. Weighing each component raw material according to the proportions, polishing the surface of each component raw material, and then mixing and melting the component raw materials to obtain a magnesium alloy melt; S2. Cooling and solidifying the magnesium alloy melt obtained in S1 to obtain a magnesium alloy ingot; S3. Machining the magnesium alloy ingot obtained in S2; S4. Solution treating the magnesium alloy ingot after machining in S3; S5. Hot extruding the magnesium alloy ingot after solution treatment in S4, and then cooling to obtain a magnesium alloy bar; S6. Aging the magnesium alloy bar obtained in S5, and then cooling to room temperature to obtain a high-strength, high-toughness, high-modulus wrought magnesium alloy.

Description

Technical Field

[0001] This invention relates to the field of magnesium alloy technology, specifically to a high-strength, high-toughness, high-modulus wrought magnesium alloy and its preparation method. Background Technology

[0002] Magnesium alloys, as one of the lightest structural metal materials currently used in engineering applications, possess characteristics such as high specific strength, high specific stiffness, excellent vibration damping performance, and good thermal conductivity and electromagnetic shielding properties. They have been widely used in aerospace, new energy vehicles, and rail transportation. In recent years, with the development of lightweight magnesium alloy structural components from general load-bearing to high load-bearing, high stiffness, and high reliability, higher comprehensive performance requirements have been placed on the strength, elastic modulus, and plasticity of magnesium alloys.

[0003] However, existing ordinary magnesium alloys are limited by their close-packed hexagonal crystal structure, resulting in a limited number of active slip systems at room temperature and insufficient coordination of plastic deformation. At the same time, the elastic modulus of ordinary magnesium alloys is generally lower than that of aluminum alloys and steel materials, making them susceptible to stiffness design constraints in load-bearing structural applications. Although ordinary magnesium alloys can achieve higher strength through rare earth alloying, plastic deformation processes, or complex heat treatment, the strength improvement is often difficult to achieve in sync with the increase in elongation after fracture and elastic modulus. This can easily lead to problems such as increased strength but decreased plasticity and limited modulus improvement. Therefore, the preparation of high-performance magnesium alloys with high strength, high ductility, and high elastic modulus remains an urgent industry challenge to be solved.

[0004] Currently, for Mg-Gd-Zn-Zr wrought magnesium alloys, higher strength can be achieved through solid solution and precipitation strengthening of Gd, synergistic effect of Zn and Gd, and grain refinement effect of Zr. However, their elastic modulus is usually still at the level of general magnesium alloys, and the improvement of structural stiffness is limited. This is mainly because strength, elongation and elastic modulus are affected by the matrix structure, precipitated phases and coarse second phases. Simply increasing the amount of strengthening phase may also cause stress concentration and decrease plasticity. Therefore, it is difficult to improve strength, elastic modulus and plasticity at the same time.

[0005] Therefore, adding Ag is one of the most common ways to improve the overall performance of Mg-Gd-Zn-Zr alloys. Ag can enhance the aging response of Mg-Gd alloys and, together with Gd, Zn and other elements, promote the formation of fine precipitates, thereby improving the yield strength and tensile strength of the alloy to a certain extent. However, the improvement of the elastic modulus of Mg-Gd-Zn-Zr-Ag alloys is still not ideal and there is room for further improvement. At the same time, it is necessary to avoid the decrease in elongation caused by coarsening, continuity or uneven distribution of the second phase.

[0006] In summary, existing wrought magnesium alloys still face the challenge of synergistically improving high strength, high elastic modulus, and high plasticity in terms of overall performance control. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a high-strength, high-toughness, and high-modulus wrought magnesium alloy and its preparation method, thereby solving the problem that existing wrought magnesium alloys are difficult to possess simultaneously high strength, high elastic modulus, and high plasticity.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A high-strength, high-toughness, high-modulus wrought magnesium alloy, by mass fraction, comprises: 11.0~13.0% Gd, 0.8~1.2% Zn, 0.3~0.7% Zr, 0.3~0.7% Ag and 0.3~0.7% Ru, with the balance being Mg and unavoidable impurities.

[0010] The present invention also provides a high-strength, high-toughness, high-modulus wrought magnesium alloy, comprising, by mass fraction: 11.0~13.0% Gd, 0.8~1.2% Zn, 0.3~0.7% Zr, 0.3~0.7% Ag, 0.3~0.7% Ru, and 3.5~4.5% Al, with the balance being Mg and unavoidable impurities.

[0011] Preferably, the Mg is made from pure magnesium, the Gd is made from Mg-30%Gd master alloy, the Zn is made from pure zinc, the Zr is made from Mg-30%Zr master alloy, the Ag is made from pure silver, the Ru is made from pure ruthenium, and the Al is made from pure aluminum.

[0012] This invention also provides a method for preparing a high-strength, high-toughness, high-modulus wrought magnesium alloy, comprising the following steps:

[0013] S1. Weigh each component raw material according to the proportion, polish the surface of each component raw material, and then mix and melt each component raw material to obtain magnesium alloy melt;

[0014] S2. After cooling and solidifying the magnesium alloy melt obtained in S1, a magnesium alloy ingot is obtained;

[0015] S3. Machining the magnesium alloy ingot obtained in S2;

[0016] S4. Perform solution treatment on the magnesium alloy ingot after S3 machining;

[0017] S5. The magnesium alloy ingot after S4 solution treatment is hot extruded and then cooled to obtain magnesium alloy rods;

[0018] S6. The magnesium alloy bar obtained in S5 is subjected to aging treatment and then cooled to room temperature to obtain a high-strength, high-toughness, high-modulus wrought magnesium alloy.

[0019] Preferably, in step S1, the specific steps of the mixed melting are as follows: under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 99:1, the Mg raw material is heated to 650~700℃ and completely melted. Then, the Gd raw material is added and stirred thoroughly until it is completely melted. Then, the temperature is raised to 700~750℃, and the remaining component raw materials are added in sequence. After being fully melted and stirred evenly, the precipitated infusible matter is removed and the temperature is held at 720~750℃ for 10~15 minutes. Finally, the surface slag is removed to obtain the magnesium alloy melt.

[0020] Preferably, in step S2, the specific method for cooling and solidification is as follows: the magnesium alloy melt obtained in S1 is poured into a metal mold, and the metal mold is placed in circulating tap water at room temperature, so that the magnesium alloy melt cools and solidifies under conditions where it does not come into direct contact with tap water.

[0021] Preferably, in step S3, the specific method of machining is as follows: after removing the irregular and defective parts on the magnesium alloy ingot obtained in S2, the middle part is taken for later use.

[0022] Preferably, in step S4, the specific method of solution treatment is as follows: the magnesium alloy ingot after machining in S3 is solution treated at 400~500℃ for 18~30h.

[0023] Preferably, in step S5, the magnesium alloy ingot after solution treatment in S4 needs to be preheated at 400~450℃ for 3~5h before hot extrusion molding. The extrusion ratio of hot extrusion molding is 9:1~25:1, and the cooling method is water cooling.

[0024] Preferably, in step S6, the specific method of the aging treatment is as follows: the magnesium alloy rod obtained in S5 is kept at 180~210℃ for 24~48h.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. In this invention, the addition of Ru to the Mg-Gd-Zn-Zr-Ag basic system promotes an increase in the amount of second-phase precipitation, maintaining its fine, discontinuous, and dispersed size. This fine second phase enhances the alloy's yield strength and tensile strength through interfacial inhibition and precipitation strengthening, while avoiding significant stress concentration caused by continuous coarse phases. This allows the elongation after fracture to be maintained and slightly improved, and the increased amount of second phase also contributes to improving the overall elastic modulus of the alloy. Further addition of Al allows for the formation of larger, high-modulus second phases, increasing their volume fraction and size hierarchy, thus significantly improving the overall elastic modulus of the alloy. Although larger second phases may negatively impact strength and plasticity, the strengthening effect of the fine second phases promoted by Ru compensates for this negative impact. Ultimately, this approach maintains improved strength, significantly increases the elastic modulus, and achieves good elongation after fracture.

[0027] 2. This invention promotes uniform distribution of alloying elements and reduces as-cast segregation through solution treatment; promotes microstructural deformation, second-phase fragmentation, and redistribution along the deformation direction through hot extrusion molding; and promotes the formation of fine precipitates through aging treatment. This allows the fine strengthening phases promoted by Ru and the larger, high-modulus phases formed by Al to redistribute during extrusion and aging, constructing a multi-scale microstructure with coarse and fine second phases coexisting. The preparation method provided by this invention achieves microstructure control and performance improvement without relying on overly complex processes, possessing high engineering application value.

[0028] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of the magnesium alloy prepared in the aged state according to Example 1 of the present invention.

[0030] Figure 2 This is a scanning electron microscope image of the magnesium alloy in the aged state prepared in Example 2 of the present invention.

[0031] Figure 3 This is a scanning electron microscope image of the magnesium alloy prepared in the aged state of Comparative Example 1 of the present invention. Detailed Implementation

[0032] To make the technical means, creative features, objectives, and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0033] Example 1

[0034] The high-strength, high-toughness, and high-modulus wrought magnesium alloy provided in this embodiment comprises, by mass fraction, 12.0% Gd, 1.0% Zn, 0.5% Zr, 0.5% Ag, and 0.5% Ru, with the balance being Mg and unavoidable impurities.

[0035] The specific preparation method is as follows:

[0036] S1. Weigh out pure magnesium, Mg-30%Gd master alloy, pure zinc, Mg-30%Zr master alloy, pure silver, and pure ruthenium according to the specified amounts. Polish the surfaces of the above raw materials. Then, under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 99:1, heat the pure magnesium to 680°C until it is completely melted. Add the Mg-30%Gd master alloy and stir thoroughly until it is completely melted. Then raise the temperature to 720°C and add the pure zinc, Mg-30%Zr master alloy, pure silver, and pure ruthenium in sequence. After fully melting and stirring evenly, remove the precipitated infusible matter and hold at 750°C for 10 minutes. Finally, remove the surface dross to obtain the magnesium alloy melt.

[0037] S2. Pour the magnesium alloy melt obtained in S1 into a metal mold, and place the metal mold in circulating tap water at room temperature, so that the magnesium alloy melt cools and solidifies without direct contact with tap water, to obtain a magnesium alloy ingot.

[0038] S3. Machining the magnesium alloy ingot obtained in S2, removing the irregular and defective parts, and taking the middle part for later use;

[0039] S4. The magnesium alloy ingot after S3 machining is solution treated at 400℃ for 24 hours;

[0040] S5. The magnesium alloy ingot after S4 solution treatment is preheated at 400℃ for 5 hours, then extruded at an extrusion ratio of 12:1, and water-cooled to obtain magnesium alloy rods.

[0041] S6. Place the magnesium alloy bar obtained in S5 in a heat treatment furnace and hold it at 200°C for 24 hours, then cool it to room temperature to obtain a high-strength, high-toughness, high-modulus deformable magnesium alloy.

[0042] Example 2

[0043] The high-strength, high-toughness, and high-modulus wrought magnesium alloy provided in this embodiment comprises, by mass fraction, 12.0% Gd, 1.0% Zn, 0.5% Zr, 0.5% Ag, 0.5% Ru, and 4.0% Al, with the balance being Mg and unavoidable impurities.

[0044] The specific preparation method is as follows:

[0045] S1. Weigh out pure magnesium, Mg-30%Gd master alloy, pure zinc, Mg-30%Zr master alloy, pure silver, pure ruthenium, and pure aluminum according to the specified amounts. Polish the surfaces of the above raw materials. Then, under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 99:1, heat the pure magnesium to 680°C until it is completely melted. Add the Mg-30%Gd master alloy and stir thoroughly until it is completely melted. Then, raise the temperature to 720°C and add the pure zinc, Mg-30%Zr master alloy, pure silver, pure ruthenium, and pure aluminum in sequence. After fully melting and stirring evenly, remove the precipitated infusible matter and hold at 750°C for 10 minutes. Finally, remove the surface slag to obtain the magnesium alloy melt.

[0046] S2. Pour the magnesium alloy melt obtained in S1 into a metal mold, and place the metal mold in circulating tap water at room temperature, so that the magnesium alloy melt cools and solidifies without direct contact with tap water, to obtain a magnesium alloy ingot.

[0047] S3. Machining the magnesium alloy ingot obtained in S2, removing the irregular and defective parts, and taking the middle part for later use;

[0048] S4. The magnesium alloy ingot after S3 machining is solution treated at 400℃ for 24 hours;

[0049] S5. The magnesium alloy ingot after S4 solution treatment is preheated at 400℃ for 5 hours, then extruded at an extrusion ratio of 12:1, and water-cooled to obtain magnesium alloy rods.

[0050] S6. Place the magnesium alloy bar obtained in S5 in a heat treatment furnace and hold it at 200°C for 24 hours, then cool it to room temperature to obtain a high-strength, high-toughness, high-modulus deformable magnesium alloy.

[0051] Comparative Example 1

[0052] The high-strength, high-toughness, high-modulus wrought magnesium alloy provided in this comparative example comprises, by mass fraction, 12.0% Gd, 1.0% Zn, 0.5% Zr, and 0.5% Ag, with the balance being Mg and unavoidable impurities.

[0053] The specific preparation method is as follows:

[0054] S1. Weigh out pure magnesium, Mg-30%Gd master alloy, pure zinc, Mg-30%Zr master alloy, and pure silver according to the specified amounts. Polish the surfaces of the above raw materials. Then, under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 99:1, heat the pure magnesium to 680°C until it is completely melted. Add the Mg-30%Gd master alloy and stir thoroughly until it is completely melted. Then, raise the temperature to 720°C and add the pure zinc, Mg-30%Zr master alloy, and pure silver in sequence. After fully melting and stirring evenly, remove the precipitated infusible matter and hold at 750°C for 10 minutes. Finally, remove the surface dross to obtain the magnesium alloy melt.

[0055] S2. Pour the magnesium alloy melt obtained in S1 into a metal mold, and place the metal mold in circulating tap water at room temperature, so that the magnesium alloy melt cools and solidifies without direct contact with tap water, to obtain a magnesium alloy ingot.

[0056] S3. Machining the magnesium alloy ingot obtained in S2, removing the irregular and defective parts, and taking the middle part for later use;

[0057] S4. The magnesium alloy ingot after S3 machining is solution treated at 400℃ for 24 hours;

[0058] S5. The magnesium alloy ingot after S4 solution treatment is preheated at 400℃ for 5 hours, then extruded at an extrusion ratio of 12:1, and water-cooled to obtain magnesium alloy rods.

[0059] S6. Place the magnesium alloy bar obtained in S5 in a heat treatment furnace and hold it at 200°C for 24 hours, then cool it to room temperature to obtain a high-strength, high-toughness, high-modulus deformable magnesium alloy.

[0060] The yield strength, tensile strength, elongation after fracture, and elastic modulus of the high-strength, high-toughness, high-modulus deformable magnesium alloys prepared in Examples 1-2 and Comparative Example 1 were tested, and the specific results are shown in Table 1.

[0061]

[0062] Table 1. Properties of high-strength, high-toughness, and high-modulus wrought magnesium alloys prepared in Examples 1-2 and Comparative Example 1

[0063] As can be seen from the data in the table above, compared with Comparative Example 1, the addition of 0.5% Ru by mass resulted in improved yield strength, tensile strength, elongation after fracture, and elastic modulus of the high-strength, high-toughness, and high-modulus deformable magnesium alloy in Example 1; and combined with... Figure 1 and Figure 3It can be seen that the number and distribution density of the second phase in Example 1 are significantly increased, and the microstructure is finer, more discontinuous and dispersed. This type of second phase not only enhances the strengthening effect, but also helps to reduce the local stress concentration caused by the coarse and continuous second phase. This is an important microstructure reason for the simultaneous improvement of yield strength, tensile strength, elongation after fracture and elastic modulus in Example 1.

[0064] Compared to Comparative Example 1, Example 2, by further adding 4.0% Al by mass on top of the added Ru, achieved an elastic modulus of 54 GPa in the high-strength, high-toughness, high-modulus deformable magnesium alloy, representing a 12.5% ​​increase over Comparative Example 1; its yield strength and tensile strength remained essentially equivalent to Comparative Example 1; and simultaneously combined with... Figure 2 and Figure 3 It is known that after the combined addition of Ru and Al elements, a certain number of large blocky bright white second phases appeared in the alloy microstructure of Example 2, while fine granular second phases and fine second phases distributed along the extrusion direction were still retained, forming a multi-scale microstructure in which coarse and fine second phases coexist. Among them, the large size and relatively high modulus of the second phase formed by Al element and the increase in its volume fraction are the main microstructural reasons for the significant increase in the elastic modulus of the high-strength, high-toughness, and high-modulus wrought magnesium alloy prepared in Example 2. At the same time, the fine second phase formed and maintained by Ru element can provide a certain strengthening effect and compensate for the strength loss caused by the larger second phase. This is also the reason why the high-strength, high-toughness, and high-modulus wrought magnesium alloy prepared in Example 2 can still maintain high yield strength and tensile strength after the addition of Al element. Thus, the high-strength, high-toughness, and high-modulus wrought magnesium alloy prepared in Example 2 can obtain a higher elastic modulus while maintaining the strength improvement effect, and achieve a synergistic match of high strength, high elastic modulus and good ductility.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-strength, high-toughness, high-modulus wrought magnesium alloy, characterized in that, It comprises, by mass fraction: 11.0–13.0% Gd, 0.8–1.2% Zn, 0.3–0.7% Zr, 0.3–0.7% Ag and 0.3–0.7% Ru, with the balance being Mg and unavoidable impurities.

2. The high-strength, high-toughness, high-modulus wrought magnesium alloy according to claim 1, characterized in that, It comprises, by mass fraction: 11.0–13.0% Gd, 0.8–1.2% Zn, 0.3–0.7% Zr, 0.3–0.7% Ag, 0.3–0.7% Ru, and 3.5–4.5% Al, with the balance being Mg and unavoidable impurities.

3. The high-strength, high-toughness, high-modulus wrought magnesium alloy according to claim 2, characterized in that, The Mg is made from pure magnesium, the Gd is made from Mg-30%Gd master alloy, the Zn is made from pure zinc, the Zr is made from Mg-30%Zr master alloy, the Ag is made from pure silver, the Ru is made from pure ruthenium, and the Al is made from pure aluminum.

4. A method for preparing a high-strength, high-toughness, high-modulus wrought magnesium alloy according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Weigh each component raw material according to the proportion, polish the surface of each component raw material, and then mix and melt each component raw material to obtain magnesium alloy melt; S2. After cooling and solidifying the magnesium alloy melt obtained in S1, a magnesium alloy ingot is obtained; S3. Machining the magnesium alloy ingot obtained in S2; S4. Perform solution treatment on the magnesium alloy ingot after S3 machining; S5. The magnesium alloy ingot after S4 solution treatment is hot extruded and then cooled to obtain magnesium alloy rods; S6. The magnesium alloy bar obtained in S5 is subjected to aging treatment and then cooled to room temperature to obtain a high-strength, high-toughness, high-modulus wrought magnesium alloy.

5. The method for preparing a high-strength, high-toughness, high-modulus wrought magnesium alloy according to claim 4, characterized in that, In step S1, the specific steps of the mixed melting are as follows: Under the protection of a mixed gas of CO2 and SF6 with a volume ratio of 99:1, the Mg raw material is heated to 650~700℃ and completely melted. Then, the Gd raw material is added and stirred thoroughly until it is completely melted. Then, the temperature is raised to 700~750℃, and the remaining component raw materials are added in sequence. After being fully melted and stirred evenly, the precipitated infusible matter is removed and the temperature is held at 720~750℃ for 10~15 minutes. Finally, the surface slag is removed to obtain the magnesium alloy melt.

6. The method for preparing a high-strength, high-toughness, high-modulus wrought magnesium alloy according to claim 4, characterized in that, In step S2, the specific method for cooling and solidification is as follows: the magnesium alloy melt obtained in S1 is poured into a metal mold, and the metal mold is placed in circulating tap water at room temperature, so that the magnesium alloy melt cools and solidifies without direct contact with tap water.

7. The method for preparing a high-strength, high-toughness, high-modulus wrought magnesium alloy according to claim 4, characterized in that, In step S3, the specific method of machining is as follows: after removing the irregular and defective parts on the magnesium alloy ingot obtained in S2, the middle part is taken for later use.

8. The method for preparing a high-strength, high-toughness, high-modulus wrought magnesium alloy according to claim 4, characterized in that, In step S4, the specific method of solution treatment is as follows: the magnesium alloy ingot after machining in S3 is solution treated at 400~500℃ for 18~30h.

9. The method for preparing a high-strength, high-toughness, high-modulus wrought magnesium alloy according to claim 4, characterized in that, In step S5, before hot extrusion molding, the magnesium alloy ingot after solution treatment in S4 needs to be preheated at 400~450℃ for 3~5 hours. The extrusion ratio for hot extrusion molding is 9:1~25:1, and the cooling method is water cooling.

10. The method for preparing a high-strength, high-toughness, high-modulus wrought magnesium alloy according to claim 4, characterized in that, In step S6, the specific method of the aging treatment is as follows: the magnesium alloy rod obtained in S5 is kept at 180~210℃ for 24~48h.

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