A high-performance wrought magnesium-lithium alloy and its preparation method

Abstract

This invention discloses a high-performance wrought magnesium-lithium alloy, comprising the following components by mass percentage: Li 4.8%~5.3%, Zn 5.7%~6.2%, Y 1.8%~2.3%, with the balance being Mg. The alloy is prepared as follows: 1. Raw materials of each component are taken according to the mass percentage of the target magnesium-lithium alloy, and smelted and cast to obtain a magnesium-lithium alloy ingot; 2. The magnesium-lithium alloy ingot is subjected to homogenization heat treatment; 3. After low-temperature preheating, it is subjected to low-temperature extrusion and cooled to room temperature. The magnesium-lithium alloy of this invention, by adding Zn and Y elements, introduces a network W phase, MgZn phase, and MgY phase as reinforcing phases to strengthen the alloy. Combined with the homogenization heat treatment followed by low-temperature extrusion deformation in the preparation process, cold forming capability is increased, and the second phase is effectively broken up, synergistically improving the strength and plastic mechanical properties of the magnesium-lithium alloy, making it suitable for aerospace and other fields.

Description

Technical Field

[0001] This invention belongs to the field of magnesium-lithium alloy material technology, specifically relating to a high-performance wrought magnesium-lithium alloy and its preparation method. Background Technology

[0002] Magnesium alloys, due to their low density, high specific strength and stiffness, excellent shielding performance, and 100% recyclability, are hailed as "green engineering materials of the 21st century" and have been widely used in aerospace, 3C electronics, and automotive manufacturing. Using Li (≤5.5% by mass) as the main alloying element to further reduce the density of magnesium alloys, while supplementing with small amounts of other elements, the resulting alloys typically exhibit a hexagonal close-packed (HCP) structure. Due to the poor natural cellular symmetry, the alloys exhibit extremely poor plasticity at room temperature, significantly limiting their further applications. Common methods for preparing wrought magnesium-lithium alloys include rolling, forging, and extrusion, all aimed at refining the alloy microstructure and reducing defects in the as-cast alloy, thereby improving the overall mechanical properties. Compared to high-temperature forming processes, low-temperature forming processes offer advantages such as high efficiency and low cost. Therefore, developing a wrought magnesium-lithium alloy with high formability and its preparation method has significant scientific necessity and positive guiding significance for large-scale production. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a high-performance wrought magnesium-lithium alloy, addressing the shortcomings of the prior art. This magnesium-lithium alloy incorporates Zn and Y elements, introducing a network W phase, MgZn phase, and MgY phase as reinforcing phases to strengthen the alloy. Combined with a pre-homogenization heat treatment followed by low-temperature extrusion deformation in the preparation process, cold forming capability is increased, and the second phase is effectively broken down. These factors synergistically improve the strength and plasticity of the magnesium-lithium alloy, solving the problem of poor strength-plasticity matching in magnesium-lithium alloys.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a high-performance wrought magnesium-lithium alloy, characterized in that, by mass percentage, it comprises the following components: Li 4.8%~5.3%, Zn 5.7%~6.2%, Y 1.8%~2.3%, with the balance being Mg.

[0005] The above-mentioned high-performance wrought magnesium-lithium alloy is characterized by comprising the following components by mass percentage: Li 4.96%, Zn 6.03%, Y 1.89%, with the balance being Mg.

[0006] Meanwhile, this invention also discloses a method for preparing the high-performance wrought magnesium-lithium alloy as described above, characterized in that the method includes the following steps: Step 1: Preparation of magnesium-lithium alloy ingots: Take each component raw material according to the mass percentage of the target product magnesium-lithium alloy, then melt them to obtain magnesium-lithium alloy melt, and then cast them to obtain magnesium-lithium alloy ingots. Step 2, Homogenization Heat Treatment: The magnesium-lithium alloy ingot obtained in Step 1 is heated and held at a constant temperature for homogenization heat treatment. Step 3, Low-temperature extrusion: The magnesium-lithium alloy ingot after homogenization heat treatment in Step 2 is preheated at a low temperature, and then extruded at a low temperature. After cooling to room temperature, a high-performance deformed magnesium-lithium alloy is obtained. The temperature of the low-temperature preheating is 80℃~150℃ and the time is 30min~60min. The temperature of the low-temperature extrusion is 80℃~150℃.

[0007] The above preparation method is characterized in that, in step one, each component raw material, including Mg, Li, Zn particles and Mg-Y master alloy, is placed in a vacuum induction furnace, and then heated to 400℃~800℃ under vacuum conditions to obtain magnesium-lithium alloy melt, which is then placed in a mold preheated to 800℃ for casting, and cooled to room temperature to obtain magnesium-lithium alloy ingot.

[0008] The preparation method described above is characterized in that the homogenization heat treatment in step two is performed at a temperature of 300°C, with a holding time of 8 hours, and the cooling method is water cooling.

[0009] The above preparation method is characterized in that the extrusion rate of the low-temperature extrusion in step three is 3 mm / s, the extrusion ratio is 16, and the air cooling is carried out to room temperature.

[0010] The above-mentioned preparation method is characterized in that the high-performance deformed magnesium-lithium alloy in step three has a tensile strength higher than 260 MPa at room temperature and an elongation after fracture exceeding 30%.

[0011] Compared with the prior art, the present invention has the following advantages: 1. This invention introduces network W phase, MgZn phase and MgY phase into a single-phase magnesium-lithium alloy by adding Zn and Y elements, which serve as reinforcing phases to strengthen the alloy and thus improve the strength of the magnesium-lithium alloy.

[0012] 2. This invention involves homogenizing the magnesium-lithium alloy ingots with heat treatment to achieve uniform grain size and random and uniform distribution of the second phase, thereby increasing its cold forming capability. Then, a low-temperature extrusion process is used for cold deformation, which refines the grains and breaks down the second phase, thus improving the mechanical properties of the magnesium-lithium alloy. At the same time, compared with conventional hot working methods, the low-temperature deformation process of this invention greatly reduces production costs and improves production efficiency, which is conducive to realizing industrial production.

[0013] 3. The present invention uses vacuum conditions in the smelting and preparation of magnesium-lithium alloy ingots, without introducing any protective atmosphere, which effectively reduces costs and avoids the introduction of pollution and impurities, and is conducive to obtaining high-performance deformed magnesium-lithium alloys.

[0014] 4. Compared with existing magnesium-lithium alloys, which have a tensile strength of over 230 MPa and an elongation after fracture exceeding 18% at room temperature, the magnesium-lithium alloy prepared by this invention has a tensile strength of over 260 MPa and an elongation after fracture exceeding 30% at room temperature. It has excellent mechanical properties, low preparation temperature and high efficiency, significantly reduces preparation costs, has obvious industrialization value, and is conducive to realizing the industrial production of magnesium-lithium alloys.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 The image shows the microstructure (OM) of the high-performance deformed magnesium-lithium alloy prepared in Example 1 of this invention.

[0017] Figure 2 This is a room temperature tensile fracture SEM image of the high-performance deformed magnesium-lithium alloy prepared in Example 1 of the present invention. Detailed Implementation

[0018] Example 1 The high-performance wrought magnesium-lithium alloy of this embodiment comprises the following components by mass percentage: Li 4.96%, Zn 6.03%, Y 1.89%, with the balance being Mg.

[0019] The preparation method of the high-performance wrought magnesium-lithium alloy in this embodiment includes the following steps: Step 1: Preparation of magnesium-lithium alloy ingots: Take each component raw material, including Mg, Li, Zn particles and Mg-Y master alloy, according to the mass percentage of the target product magnesium-lithium alloy and put them into a vacuum induction furnace. Then, heat them to 400℃~800℃ under vacuum conditions to melt them to obtain magnesium-lithium alloy melt. Then, place it in a mold preheated to 800℃ for casting and cool it to room temperature to obtain magnesium-lithium alloy ingots. Step 2, Homogenization heat treatment: The magnesium-lithium alloy ingot obtained in Step 1 is subjected to homogenization heat treatment at 300℃ for 8 hours, followed by water cooling. Step 3, Low-temperature extrusion: The magnesium-lithium alloy ingot after homogenization heat treatment in step 2 is preheated at 100℃ for 30 minutes, and then subjected to low-temperature extrusion at 100℃ with an extrusion rate of 3 mm / s and an extrusion ratio of 16. After air cooling to room temperature, a high-performance deformed magnesium-lithium alloy is obtained.

[0020] The room temperature mechanical properties of the magnesium-lithium alloy ingot prepared in step one and the deformed magnesium-lithium alloy obtained in step three of this embodiment are shown in Table 1 below.

[0021] Table 1

[0022] As shown in Table 1, compared with the cast magnesium-lithium alloy, the present invention achieves deformation through low-temperature extrusion, which effectively improves the mechanical properties of the magnesium-lithium alloy.

[0023] Figure 1 The OM image shows the microstructure of the high-performance wrought magnesium-lithium alloy prepared in this embodiment. Figure 1 It can be seen that the grain size of the magnesium-lithium alloy obtained after low-temperature extrusion is about 2.9 μm, and the second phase is randomly distributed along the extrusion direction.

[0024] Figure 2 The image shows a room-temperature tensile fracture surface SEM image of the high-performance wrought magnesium-lithium alloy prepared in this embodiment. Figure 2 It can be seen that the tensile fracture surface exhibits dimples of uniform size, indicating that the fracture mode of this alloy is ductile fracture.

[0025] Example 2 The high-performance wrought magnesium-lithium alloy of this embodiment comprises the following components by mass percentage: Li 4.8%, Zn 5.7%, Y 2.3%, with the balance being Mg.

[0026] The preparation method of the high-performance wrought magnesium-lithium alloy in this embodiment includes the following steps: Step 1: Preparation of magnesium-lithium alloy ingots: Take each component raw material, including Mg, Li, Zn particles and Mg-Y master alloy, according to the mass percentage of the target product magnesium-lithium alloy and put them into a vacuum induction furnace. Then, heat them to 400℃~800℃ under vacuum conditions to melt them to obtain magnesium-lithium alloy melt. Then, place it in a mold preheated to 800℃ for casting and cool it to room temperature to obtain magnesium-lithium alloy ingots. Step 2, Homogenization heat treatment: The magnesium-lithium alloy ingot obtained in Step 1 is subjected to homogenization heat treatment at 300℃ for 8 hours, followed by water cooling. Step 3, Low-temperature extrusion: The magnesium-lithium alloy ingot after homogenization heat treatment in step 2 is preheated at 80℃ for 60 min, and then subjected to low-temperature extrusion at 80℃ with an extrusion rate of 3 mm / s and an extrusion ratio of 16. After air cooling to room temperature, a high-performance deformed magnesium-lithium alloy is obtained.

[0027] Testing revealed that the high-performance deformable magnesium-lithium alloy prepared in this embodiment exhibits a tensile strength exceeding 270 MPa at room temperature and an elongation after fracture exceeding 31%.

[0028] Example 3 The high-performance wrought magnesium-lithium alloy of this embodiment comprises the following components by mass percentage: Li 5.3%, Zn 6.2%, Y 1.8%, with the balance being Mg.

[0029] The preparation method of the high-performance wrought magnesium-lithium alloy in this embodiment includes the following steps: Step 1: Preparation of magnesium-lithium alloy ingots: Take each component raw material, including Mg, Li, Zn particles and Mg-Y master alloy, according to the mass percentage of the target product magnesium-lithium alloy and put them into a vacuum induction furnace. Then, heat them to 400℃~800℃ under vacuum conditions to melt them to obtain magnesium-lithium alloy melt. Then, place it in a mold preheated to 800℃ for casting and cool it to room temperature to obtain magnesium-lithium alloy ingots. Step 2, Homogenization heat treatment: The magnesium-lithium alloy ingot obtained in Step 1 is subjected to homogenization heat treatment at 300℃ for 8 hours, followed by water cooling. Step 3, Low-temperature extrusion: The magnesium-lithium alloy ingot after homogenization heat treatment in step 2 is preheated at 150℃ for 45 minutes, and then subjected to low-temperature extrusion at 150℃ with an extrusion rate of 3 mm / s and an extrusion ratio of 16. After air cooling to room temperature, a high-performance deformed magnesium-lithium alloy is obtained.

[0030] Testing showed that the tensile strength of the deformed magnesium-lithium alloy prepared in this embodiment was 281 MPa at room temperature, and the elongation after fracture was 35%.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A high-performance wrought magnesium-lithium alloy, characterized in that, It comprises the following components by mass percentage: Li 4.8%~5.3%, Zn 5.7%~6.2%, Y 1.8%~2.3%, with the balance being Mg.

2. The high-performance wrought magnesium-lithium alloy according to claim 1, characterized in that, The composition by mass percentage is as follows: Li 4.96%, Zn 6.03%, Y 1.89%, with the balance being Mg.

3. A method for preparing the high-performance wrought magnesium-lithium alloy as described in claim 1 or 2, characterized in that, The method includes the following steps: Step 1: Preparation of magnesium-lithium alloy ingots: Take each component raw material according to the mass percentage of the target product magnesium-lithium alloy, then melt them to obtain magnesium-lithium alloy melt, and then cast them to obtain magnesium-lithium alloy ingots. Step 2, Homogenization Heat Treatment: The magnesium-lithium alloy ingot obtained in Step 1 is heated and held at a constant temperature for homogenization heat treatment. Step 3, Low-temperature extrusion: The magnesium-lithium alloy ingot after homogenization heat treatment in Step 2 is preheated at a low temperature, and then extruded at a low temperature. After cooling to room temperature, a high-performance deformed magnesium-lithium alloy is obtained. The temperature of the low-temperature preheating is 80℃~150℃ and the time is 30min~60min. The temperature of the low-temperature extrusion is 80℃~150℃.

4. The preparation method according to claim 3, characterized in that, In step one, each component raw material, including Mg, Li, Zn particles and Mg-Y master alloy, is placed in a vacuum induction furnace and then heated to 400℃~800℃ under vacuum conditions to obtain magnesium-lithium alloy melt. The melt is then placed in a mold preheated to 800℃ for casting and cooled to room temperature to obtain magnesium-lithium alloy ingot.

5. The preparation method according to claim 3, characterized in that, The homogenization heat treatment in step two is performed at a temperature of 300°C for 8 hours, and the cooling method is water cooling.

6. The preparation method according to claim 3, characterized in that, The extrusion rate of the low-temperature extrusion described in step three is 3 mm / s, the extrusion ratio is 16, and it is air-cooled to room temperature.

7. The preparation method according to claim 3, characterized in that, The high-performance wrought magnesium-lithium alloy described in step three has a tensile strength of over 260 MPa at room temperature and an elongation after fracture exceeding 30%.

Images