High-performance magnesium alloy and preparation method thereof

Abstract

The application discloses a high-performance magnesium alloy and a preparation method thereof, and belongs to the technical field of alloy materials.The preparation method comprises the following steps: mixing magnesium alloy raw materials, melting the mixed magnesium alloy raw materials, casting the melted magnesium alloy into a blank, then performing hot rolling and solid solution treatment, subsequently performing multi-directional compression at a liquid nitrogen temperature, and finally performing annealing treatment, so that the high-performance magnesium alloy is obtained.The high-performance magnesium alloy material prepared by the application has a high-density twin crystal network which is longitudinally and transversely intersected in the grain, and solute atoms are periodically enriched on the twin crystal boundary to stabilize the twin crystal boundary, which not only effectively hinders dislocation movement, but also reduces stress concentration at the interface, so that the strength and plasticity of the magnesium alloy are synergistically improved.

Description

Technical Field

[0001] This invention belongs to the field of alloy materials technology, and particularly relates to a high-performance magnesium alloy and its preparation method. Background Technology

[0002] Magnesium alloys, with a density of 1.7-1.9 g / cm³, are approximately one-quarter the density of steel and two-thirds that of aluminum alloys, making them promising lightweight materials. However, the weak intrinsic bonding between magnesium atoms and the insufficient slip system at room temperature due to their close-packed cubic structure result in low strength, poor ductility, and overall unsatisfactory mechanical properties, significantly limiting their industrial applications. Introducing incoherent interfaces such as phase boundaries (second-phase strengthening) and grain boundaries (grain refinement strengthening) into magnesium alloys is an effective strengthening method, significantly improving strength by hindering dislocation movement. However, the large dislocation pile-up at the interface easily leads to stress concentration, causing cracks to preferentially initiate at incoherent interfaces, thus reducing the ductility of magnesium alloys—a reversal between strength and ductility. Twin boundaries formed through twinning in magnesium alloys are coherent interfaces with low energy and minimal stress concentration, making them a more ideal way to synergistically improve both strength and ductility. However, on the one hand, the density of twin boundaries in fine-grained magnesium alloys is easily limited, making it difficult to achieve economies of scale; on the other hand, ordinary twin boundaries are prone to migration or even annihilation through detwining during deformation, resulting in poor twin boundary stability and limited improvement in the strength and plasticity of magnesium alloys.

[0003] It is evident that existing methods that introduce interfaces improve the strength of magnesium alloys at the expense of ductility, or fail to achieve satisfactory strengthening effects. Therefore, how to provide a coherent and stable interface to achieve a synergistic improvement in the strength and ductility of magnesium alloys is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a high-performance magnesium alloy and its preparation method. This invention presents a high-performance magnesium alloy and its preparation method based on gravity casting, hot rolling, solution treatment, multi-directional compression, and annealing to prepare a high-density twin network, with solute atoms periodically distributed at the twin boundaries to significantly stabilize the interface.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a high-performance magnesium alloy, comprising the following steps: mixing and melting magnesium alloy raw materials, casting them into a billet, hot rolling and solution treatment, followed by multi-directional compression at liquid nitrogen temperature, and finally annealing to obtain the high-performance magnesium alloy.

[0006] Furthermore, the magnesium alloy raw material is a magnesium alloy ingot prepared by gravity method.

[0007] This invention first involves hot rolling a magnesium alloy ingot prepared by gravity to eliminate casting defects and microstructures such as shrinkage porosity and dendrites. Then, dynamic recovery recrystallization is used to form coarse equiaxed crystals. Simultaneously, a solution treatment is performed to eliminate the second phase, forming a supersaturated solid solution. Subsequently, to obtain a high-density, interwoven twin network, the magnesium alloy undergoes triaxial compression (x, y, z). To prevent solute element precipitation and reduce dislocation movement to increase twin density, the compression is performed at liquid nitrogen temperature. Finally, annealing is used to achieve periodic enrichment of solute atoms at the twin boundaries. This invention, by preparing a coarse-grained magnesium alloy and introducing a high-density twin network, while simultaneously stabilizing the twin boundaries through periodic enrichment of solute atoms, not only effectively hinders dislocation movement but also reduces stress concentration at the interface, ultimately achieving a synergistic improvement in the strength and plasticity of the magnesium alloy.

[0008] Furthermore, the melting is carried out under a protective atmosphere, and the melting temperature is 700℃-740℃.

[0009] Furthermore, the protective atmosphere is an SF6+CO2 protective atmosphere, wherein the volume ratio of SF6 to CO2 is 1:100.

[0010] Furthermore, the temperature for casting the billet is 60℃-90℃.

[0011] Furthermore, the hot rolling temperature is 400℃-550℃.

[0012] Furthermore, the solution treatment temperature is 500℃-550℃, and the solution treatment time is 1h-3h.

[0013] Furthermore, the number of passes for the multi-directional compression is 1-3.

[0014] Furthermore, the annealing temperature is 200℃-400℃, and the annealing time is 1h-4h.

[0015] The present invention also provides a high-performance magnesium alloy prepared by the above method.

[0016] The high-performance magnesium alloy material prepared by this invention has a high-density twin network with interlaced grains. At the same time, solute atoms periodically enrich and stabilize the twin boundaries, which not only effectively hinders dislocation movement but also reduces stress concentration at the interface, ultimately achieving a synergistic improvement in the strength and plasticity of the magnesium alloy.

[0017] Furthermore, the mass ratio of the metal elements in the high-performance magnesium alloy is Mg:Zn:Gd = 96:2:2.

[0018] Furthermore, the mass ratio of the metal elements in the high-performance magnesium alloy is Mg:Zn:Ca = 97:2:1.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: The magnesium alloy prepared by this invention consists of coarse equiaxed crystals and a high-density twin network with interwoven grains. The twin boundaries are fully coherent interfaces, and solute atoms are periodically enriched at these boundaries. During deformation, on the one hand, the high-density twins effectively shorten the mean free path of dislocation slip, thus hindering dislocation movement. Simultaneously, the periodic enrichment of solute atoms at the twin boundaries effectively pins them, stabilizing them in interactions with dislocations, stacking faults, and other defects, resulting in superior strengthening effects. On the other hand, twin boundaries can emit different types of dislocations under certain loads, improving the material's work hardening ability. During deformation, some dislocations can propagate through the twin boundaries, preventing severe pile-up and effectively reducing stress concentration at the interfaces, thereby significantly improving the plasticity of the magnesium alloy. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the x, y, and z-axis compression directions of the multi-directional compression technology used in this invention. Figure 2 The images show the optical microstructure of the Mg-2Zn-2Gd (wt.%) magnesium alloy material in Example 1 after one pass of multi-directional compression and annealing at 200°C for 1 hour, at different magnifications. (a) is 100 μm and (b) is 25 μm. Figure 3 The images show STEM-HAADF and EDS elemental surface scans of the twin boundaries of the Mg-2Zn-2Gd (wt.%) magnesium alloy material in Example 1 after one pass of multi-directional compression and annealing at 200°C for 1 hour. Figure 4 The images show the optical microstructure of the Mg-2Zn-2Gd (wt.%) magnesium alloy material in Example 2 after one pass of multi-directional compression and annealing at 220°C for 1 hour, at different magnifications. (a) is 100 μm and (b) is 25 μm. Figure 5 The images show the optical microstructure of the Mg-2Zn-2Gd (wt.%) magnesium alloy material in Example 3 after two passes of multi-directional compression and annealing at 300°C for 2 hours, at different magnifications. (a) is 100 μm and (b) is 25 μm. Figure 6The images show the optical microstructure of the Mg-2Zn-2Gd (wt.%) magnesium alloy material in Example 4 after three passes of multi-directional compression and annealing at 400℃ for 4 hours, at different magnifications. (a) is 100 μm and (b) is 25 μm. Figure 7 The images show the optical microstructure of the Mg-2Zn-2Gd (wt.%) magnesium alloy material in Comparative Example 1 after hot rolling at 550℃ and solution treatment at 550℃ for 2 hours at different magnifications, where (a) is 100 μm and (b) is 25 μm. Figure 8 The images show the optical microstructure of the Mg-2Zn-2Gd (wt.%) magnesium alloy material in Comparative Example 2 after hot rolling at 550℃, solution treatment at 550℃ for 2 hours, and one pass of multi-directional compression at different magnifications. (a) is 100 μm and (b) is 25 μm. Figure 9 The images show STEM-HAADF and EDS elemental surface scans of the twin boundaries of the Mg-2Zn-2Gd (wt.%) magnesium alloy material in Comparative Example 2 after hot rolling at 550℃, solution treatment at 550℃ for 2 hours, and one pass of multi-directional compression. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] The present invention provides a method for preparing a high-performance magnesium alloy, comprising the following steps: mixing and melting magnesium alloy raw materials, casting them into billets, hot rolling and solution treatment, followed by multi-directional compression at liquid nitrogen temperature, and finally annealing to obtain the high-performance magnesium alloy.

[0027] In a preferred embodiment of the present invention, the magnesium alloy raw material is a magnesium alloy ingot prepared by gravity method.

[0028] In a preferred embodiment of the present invention, melting is carried out under a protective atmosphere, and the melting temperature is 700°C-740°C. The protective atmosphere is an SF6+CO2 protective atmosphere, wherein the volume ratio of SF6 to CO2 is 1:100.

[0029] In a preferred embodiment of the present invention, the casting temperature is 60°C-90°C.

[0030] In a preferred embodiment of the present invention, the hot rolling temperature is 400°C-550°C.

[0031] In a preferred embodiment of the present invention, the solution treatment temperature is 500℃-550℃ and the solution treatment time is 1h-3h.

[0032] In a preferred embodiment of the present invention, the number of passes for multi-directional compression is 1-3.

[0033] In a preferred embodiment of the present invention, the annealing temperature is 200℃-400℃ and the annealing time is 1h-4h.

[0034] Embodiments of the present invention also provide a high-performance magnesium alloy prepared by the above method.

[0035] In a preferred embodiment of the present invention, the mass ratio of metal elements in the high-performance magnesium alloy is Mg:Zn:Gd = 96:2:2.

[0036] In a preferred embodiment of the present invention, the mass ratio of metal elements in the high-performance magnesium alloy is Mg:Zn:Ca = 97:2:1.

[0037] In the following embodiments and comparative examples of the present invention, the performance testing standard for magnesium alloys is GB / T 16865-2023 "Tension Test Specimens and Methods for Processed Products of Wrought Aluminum, Magnesium and Their Alloys".

[0038] In the following embodiments and comparative examples of the present invention, the Mg-Gd master alloy is a Mg-Zn-Gd alloy, and its chemical composition is: Mg- x Zn- y Gd (wt.%), where 0.8 ≤ x ≤2.5, 0.9≤ y ≤2.4. The Mg-Ca master alloy is a Mg-Zn-Ca alloy, and its chemical composition is: Mg- x Zn- y Ca (wt.%), where 0.9 ≤ x ≤2.3, 0.5≤ y ≤1.5.

[0039] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0040] All raw materials used in the embodiments of the present invention were obtained through commercial purchase.

[0041] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0042] The technical solution of the present invention will be further illustrated by the following embodiments.

[0043] Example 1 A method for preparing a high-performance magnesium alloy, comprising the following steps: Magnesium ingots (prepared by gravity method, the same below), zinc ingots, and Mg-Gd master alloy were placed in a melting furnace according to the target alloy composition Mg-2Zn-2Gd (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100, volume ratio, the same below) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added (i.e., the amount of hexachloroethane added was 1.5% of the total mass of the raw materials) for refining and slag removal. The mixture was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the magnesium alloy billet was obtained. The magnesium alloy billet was heated in a furnace at 550℃ and immediately hot-rolled, followed by solution treatment at 550℃ for 2 hours, and then water quenched. The water-quenched sample was subjected to triaxial multi-directional compression in the x, y, and z axes at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1As shown, the compression pass was 1, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively. The sample after multi-directional compression was then annealed at 200℃ for 1 hour to obtain a high-performance magnesium alloy.

[0044] The obtained high-performance magnesium alloy has a tensile strength of 455 MPa and an elongation at break of 16.9%. An optical microstructure photograph of this high-performance magnesium alloy is shown below. Figure 2 STEM-HAADF and EDS elemental plane distribution images of twin boundaries are shown below. Figure 3 .Depend on Figure 2 It can be seen that a high-density twin network exists within the coarse-grained magnesium alloy grains; Figure 3 It can be seen that the solute element Zn is periodically enriched at the twin boundaries, which acts as a pinning effect on the movement of the twin boundaries.

[0045] Example 2 A method for preparing a high-performance magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Gd master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-2Gd (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the melt was removed to obtain a magnesium alloy billet. The magnesium alloy billet was heated in a furnace at 400℃ and immediately hot-rolled, followed by solution treatment at 500℃ for 3 hours, and then water quenched. The water-quenched sample was then subjected to triaxial multi-directional compression in the x, y, and z axes at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1 As shown, the compression pass was 1, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively. The sample after multi-directional compression was then annealed at 220℃ for 1 hour to obtain a high-performance magnesium alloy.

[0046] The obtained high-performance magnesium alloy has a tensile strength of 345 MPa and an elongation at break of 18.6%. An optical microstructure photograph of this high-performance magnesium alloy is shown below. Figure 4 It can be seen that there is a high-density twin network crisscrossing inside the coarse-grained magnesium alloy grains.

[0047] Example 3 A method for preparing a high-performance magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Gd master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-2Gd (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the mold was removed to obtain a magnesium alloy billet. The magnesium alloy billet was heated in a furnace at 500℃ and immediately hot-rolled, followed by solution treatment at 500℃ for 1 hour, and then water quenched. The water-quenched sample was then subjected to triaxial multi-directional compression in the x, y, and z axes at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1 As shown, the compression passes were performed twice, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively. The samples after multi-directional compression were then annealed at 300℃ for 2 hours to obtain a high-performance magnesium alloy.

[0048] The obtained high-performance magnesium alloy has a tensile strength of 412 MPa and an elongation at break of 15.7%. An optical microstructure photograph of this high-performance magnesium alloy is shown below. Figure 5 It can be seen that there is a high-density twin network crisscrossing inside the coarse-grained magnesium alloy grains.

[0049] Example 4 A method for preparing a high-performance magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Gd master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-2Gd (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the mold was removed to obtain a magnesium alloy billet. The magnesium alloy billet was heated in a furnace at 400℃ and immediately hot-rolled, followed by solution treatment at 520℃ for 2 hours, and then water quenched. The water-quenched sample was then subjected to triaxial multi-directional compression (x, y, z) at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1 As shown, the compression passes were three times, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively. The samples after multi-directional compression were then annealed at 400℃ for 4 hours to obtain a high-performance magnesium alloy.

[0050] The obtained high-performance magnesium alloy has a tensile strength of 397 MPa and an elongation at break of 14.9%. An optical microstructure photograph of this high-performance magnesium alloy is shown below. Figure 6 It can be seen that there is a high-density twin network crisscrossing inside the coarse-grained magnesium alloy grains.

[0051] Example 5 A method for preparing a high-performance magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Ca master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-1Ca (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the melt was removed to obtain a magnesium alloy billet. The magnesium alloy billet was heated in a furnace at 550℃ and immediately hot-rolled, followed by solution treatment at 550℃ for 2 hours, and then water quenched. The water-quenched sample was then subjected to triaxial multi-directional compression in the x, y, and z axes at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1 As shown, the compression pass was 1, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively. The sample after multi-directional compression was then annealed at 200℃ for 1 hour to obtain a high-performance magnesium alloy.

[0052] The resulting high-performance magnesium alloy has a tensile strength of 412 MPa and a fracture elongation of 16.5%. The coarse-grained magnesium alloy of this high-performance magnesium alloy contains a high-density twin network with interlaced grains.

[0053] Example 6 A method for preparing a high-performance magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Ca master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-1Ca (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the melt was removed to obtain a magnesium alloy billet. The magnesium alloy billet was heated in a furnace at 400℃ and immediately hot-rolled, followed by solution treatment at 500℃ for 3 hours, and then water quenched. The water-quenched sample was then subjected to triaxial multi-directional compression in the x, y, and z axes at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1As shown, the compression pass was 1, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively. The sample after multi-directional compression was then annealed at 220℃ for 1 hour to obtain a high-performance magnesium alloy.

[0054] The resulting high-performance magnesium alloy has a tensile strength of 365 MPa and a fracture elongation of 14.7%. The coarse-grained magnesium alloy grains of this high-performance magnesium alloy contain a crisscrossing high-density twin network.

[0055] Example 7 A method for preparing a high-performance magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Ca master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-1Ca (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 90℃. After cooling, the melt was removed to obtain a magnesium alloy billet. The magnesium alloy billet was heated in a furnace at 500℃ and immediately hot-rolled, followed by solution treatment at 500℃ for 1 hour, and then water quenched. The water-quenched sample was then subjected to triaxial multi-directional compression in the x, y, and z axes at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1 As shown, the compression passes were performed twice, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively. The samples after multi-directional compression were then annealed at 300℃ for 2 hours to obtain a high-performance magnesium alloy.

[0056] The resulting high-performance magnesium alloy has a tensile strength of 371 MPa and a fracture elongation of 15.1%. The coarse-grained magnesium alloy grains of this high-performance magnesium alloy contain a crisscrossing high-density twin network.

[0057] Example 8 A method for preparing a high-performance magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Ca master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-1Ca (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 60℃. After cooling, the mold was removed to obtain a magnesium alloy billet. The magnesium alloy billet was heated in a furnace at 400℃ and immediately hot-rolled, followed by solution treatment at 520℃ for 2 hours, and then water quenched. The water-quenched sample was then subjected to triaxial multi-directional compression in the x, y, and z axes at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1 As shown, the compression passes were three times, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively. The samples after multi-directional compression were then annealed at 400℃ for 4 hours to obtain a high-performance magnesium alloy.

[0058] The resulting high-performance magnesium alloy has a tensile strength of 338 MPa and a fracture elongation of 13.9%. The coarse-grained magnesium alloy of this high-performance magnesium alloy contains a high-density twin network with interlaced grains.

[0059] Comparative Example 1 A method for preparing a magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Gd master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-2Gd (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the melt was removed to obtain a magnesium alloy billet. The magnesium alloy billet was then heated in a furnace at 550℃ and immediately hot-rolled, followed by solution treatment at 550℃ for 2 hours. Finally, it was water-quenched to obtain the magnesium alloy.

[0060] The optical microstructure of this comparative magnesium alloy is shown in the following image. Figure 7 As shown, due to the lack of multi-directional compression and annealing treatment, no twin network was formed inside the magnesium alloy grains. As a result, the mechanical properties of the magnesium alloy obtained at this time are relatively low, with a tensile strength of 244 MPa and a fracture elongation of 7.9%.

[0061] Comparative Example 2 A method for preparing a magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Gd master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-2Gd (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the melt was removed to obtain a magnesium alloy billet. The magnesium alloy billet was heated in a furnace at 550℃ and immediately hot-rolled, followed by solution treatment at 550℃ for 2 hours, and then water quenched. The water-quenched sample was then subjected to triaxial multi-directional compression in the x, y, and z axes at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1 As shown, the compression pass is 1, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively, to obtain magnesium alloy.

[0062] The optical microstructure of this comparative magnesium alloy is shown in the following image. Figure 8 As shown, after multi-directional compression, a high-density twin network is formed inside the coarse-grained magnesium alloy. The STEM-HAADF and EDS elemental surface scan images of this comparative magnesium alloy are shown below. Figure 9 As shown, due to the lack of annealing treatment, no periodic enrichment of solute atoms formed at the twin boundaries. Because of the lack of pinning effect of solute atoms on the twin boundaries, the resulting magnesium alloy has relatively low mechanical properties, with a tensile strength of 295 MPa and a fracture elongation of 11.8%.

[0063] Comparative Example 3 A method for preparing a magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Ca master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-1Ca (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the melt was removed to obtain a magnesium alloy billet. The magnesium alloy billet was then heated in a furnace at 550℃ and immediately hot-rolled, followed by solution treatment at 550℃ for 2 hours. Finally, it was water-quenched to obtain the magnesium alloy.

[0064] Because multi-directional compression and annealing were not performed, no twin network was formed inside the magnesium alloy grains. As a result, the mechanical properties of the magnesium alloy obtained at this time were relatively low, with a tensile strength of 213 MPa and a fracture elongation of 6.9%.

[0065] Comparative Example 4 A method for preparing a magnesium alloy, comprising the following steps: Magnesium ingots, zinc ingots, and Mg-Ca master alloys were placed in a melting furnace according to the target alloy composition Mg-2Zn-1Ca (wt.%). The mixture was heated to 740℃ under a protective atmosphere of SF6+CO2 (SF6:CO2=1:100) to prevent oxidation, until completely melted. Then, 1.5wt.% hexachloroethane was added for refining, and the slag was removed. The melt was then cast into a metal mold (φ38×250mm) preheated to 80℃. After cooling, the melt was removed to obtain a magnesium alloy billet. The magnesium alloy billet was heated in a furnace at 550℃ and immediately hot-rolled, followed by solution treatment at 550℃ for 2 hours, and then water quenched. The water-quenched sample was then subjected to triaxial multi-directional compression in the x, y, and z axes at liquid nitrogen temperature. The specific compression directions are as follows... Figure 1 As shown, the compression pass is 1, with pressures along the x, y, and z axes of 98 MPa, 30 MPa, and 20 MPa, respectively, to obtain magnesium alloy.

[0066] After multi-directional compression, a high-density twin network is formed inside the coarse-grained magnesium alloy. However, due to the lack of annealing treatment, no periodic enrichment of solute atoms is formed at the twin boundaries. Due to the lack of pinning effect of solute atoms on the twin boundaries, the resulting magnesium alloy has relatively low mechanical properties, with a tensile strength of 298 MPa and a fracture elongation of 10.2%.

[0067] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance magnesium alloy, characterized in that, Includes the following steps: Magnesium alloy raw materials are mixed and melted, then cast into billets, followed by hot rolling, solution treatment and water quenching, then multi-directional compression at liquid nitrogen temperature, and finally annealing to obtain the high-performance magnesium alloy. The magnesium alloy raw material is a magnesium alloy ingot prepared by gravity method, and the mass ratio of metal elements in the high-performance magnesium alloy is Mg:Zn:Gd = 96:2:2 or Mg:Zn:Ca = 97:2:

1. The melting is carried out under a protective atmosphere and the melting temperature is 700℃-740℃; The hot rolling temperature is 400℃-550℃; The solution treatment temperature is 500℃-550℃, and the solution treatment time is 1h-3h; The multi-directional compression passes 1-3 times; The annealing temperature is 200℃-400℃, and the annealing time is 1h-4h.

2. A high-performance magnesium alloy, characterized in that, It is prepared according to the preparation method according to claim 1.

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