Mg-sc magnesium alloy with high strength and medium plasticity at room temperature and preparation method thereof

Abstract

This invention discloses a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy and its preparation method, belonging to the technical field of magnesium alloy materials. This invention uses pure Sc and Mg-30wt%Sc alloy as raw materials to formulate a Mg-35wt%Sc alloy. Through vacuum melting, homogenization solution treatment, hot extrusion, heat treatment, and different cooling methods, a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy is obtained, solving the problem of insufficient comprehensive mechanical properties of existing Mg-Sc alloys.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy materials technology, and particularly relates to a room temperature high-strength and medium-plasticity Mg-Sc magnesium alloy and its preparation method. Background Technology

[0002] Magnesium and its alloys are widely considered promising candidates for structural materials in the medical, automotive, and aerospace fields due to their excellent biocompatibility, high specific strength, and lightweight properties. However, due to the anisotropy of the hexagonal close-packed (hcp) structure (α phase), traditional magnesium alloys with an hcp structure (α phase) (such as the Mg-Ca, Mg-Zn, and Mg-Al series) typically exhibit poor ductility during room temperature deformation. Attempts have been made to introduce an isotropic body-centered cubic (bcc) structure (β phase) into traditional magnesium alloys to fundamentally improve their ductility. It is well known that isotropic β-type Mg-Li alloys with a bcc structure can achieve excellent plastic deformation capabilities because metals with a bcc structure have more slip systems than those with an hcp structure. Therefore, one practical method to improve the ductility of magnesium alloys is to transform the phase structure from an hcp structure to a bcc structure.

[0003] Scandium (Sc) is widely used as an alloying element in aluminum alloys in aerospace, automotive, and other fields. For example, it is beneficial for grain refinement, which can improve the mechanical properties and corrosion resistance of magnesium alloys. Regarding mechanical properties, it is well known that the maximum solid solubility of scandium in Mg is 24.5 wt%. Therefore, the mechanical properties of magnesium alloys can be improved through the solid solution strengthening effect. Most importantly, Sc is the only rare earth element that can transform the Mg matrix from an hcp structure to a bcc structure. Notably, Ogawa et al. reported that a β-type Mg-20.5 at% Sc alloy exhibited 4.4% superelastic behavior at -150 °C. In a β-type Mg-18.3 at% Sc alloy, a significant shape memory effect was observed during heating to room temperature. They attributed the shape memory effect and superelasticity to the thermoelastic martensitic phase transformation between the orthorhombic α' phase and the bcc structure β phase in the β-type Mg-Sc alloy. These significant findings have sparked considerable interest in Mg-Sc alloys with high Sc content.

[0004] In the field of Mg-Sc alloy research, the paper "The Influence of Sc on the Mechanical Properties and Corrosion Resistance of Pure Magnesium" (Zhang Manyu, Shanghai Jiao Tong University, 2018. DOI:10.27307 / d.cnki.gsjtu.2018.003459) published relevant studies on the room temperature tensile mechanical properties of a series of binary Mg-Sc alloys (Mg-2wt%Sc, Mg-5wt%Sc, Mg-10wt%Sc, and Mg-15wt%Sc). Among them, the Mg-5wt%Sc alloy had the worst comprehensive mechanical properties, with an ultimate tensile strength (UTS) of only about 120 MPa and an elongation of only 7.6%. The Mg-10wt%Sc alloy, which had the best comprehensive mechanical properties, also had a UTS of only about 143 MPa and an elongation of only about 10.3%, which greatly limited the direct application of Mg-Sc alloys as mechanical structural materials. The paper "Influence of Y on the Mechanical and Corrosion Properties of Mg-Sc Binary Alloys" (Xu Xinmei, Shanghai Jiao Tong University, 2019.DOI:10.27307 / d.cnki.gsjtu.2019.002983) discloses the room temperature tensile mechanical properties of Mg-5Sc, Mg-5Sc-0.5Y, Mg-5Sc-1Y, Mg-5Sc-2Y, Mg-5Sc-3Y, and Mg-5Sc-3.5Y (wt%) alloys. Among them, the tensile yield strength (YS) and elongation of the Mg-5Sc alloy without added Y are only about 70 MPa and 9.0%, respectively. The YS and elongation of the Mg-5Sc-3Y alloy, which has the best overall mechanical properties, are only about 107 MPa and 15.5%, respectively. This also limits the direct industrial application of Mg-Sc alloys as mechanical structural materials. Chinese patent application number 202311034348.8 discusses the mechanical properties of a series of medical-grade Mg-Sc magnesium alloys (Mg-0.5wt%Sc, Mg-1wt%Sc, Mg-3wt%Sc, and Mg-5wt%Sc). The Mg-0.5wt%Sc alloy, with the worst mechanical properties, has a UTS of only 198 MPa, while the Mg-3wt%Sc alloy, with the best mechanical properties, has a UTS of only 245 MPa. Although both alloys have an elongation exceeding 37.2%, their overall mechanical properties remain relatively low.In the field of non-Mg-Sc alloy research, the room temperature tensile mechanical properties of AZ31 alloy were reported in "Microstructure and mechanical properties of wire and arc additive manufactured AZ31 magnesium alloy using cold metal transfer process" (X.Yang, J.Liu, Z.Wang, X.Lin, F.Liu, W.Huang, E.Liang, Mater.Sci.Eng.A774(2020)138942). Among them, the AZ31 with the best mechanical properties has a UTS and elongation of only about 210.5 MPa and 10.55%, respectively. The mechanical properties of ZK30 series magnesium alloys were studied in the paper "Thermalstability, grain growth, kinetics, mechanical properties, and bio-corrosion resistance of pure Mg, ZK30, and ZEK300 alloys: A comparative study" (Z. Savadei, H. Mirzadeh, R. Aghdam, R. Mahmudi, Mater. Today Commun. 33 (2022) 104825). The study showed that the UTS and elongation of ZK30 magnesium alloys were only about 260.1 MPa and 10.60%, respectively. Meanwhile, the mechanical properties of ZK60 series magnesium alloys were discussed in "Evolution of the microstructure, texture and mechanical properties of ZK60 alloy during processing by rotating shear extrusion" (L. Yan, Z. Zhang, G. Li, Y. Xue, J. Xu, J. Alloy. Compd. 877(2021) 160229). This study showed that the UTS and elongation of ZK60 magnesium alloy were only about 278.0 MPa and 10.00%, respectively. Obviously, these magnesium alloys still have low overall mechanical properties. Therefore, it is necessary to further improve the overall mechanical properties of magnesium alloys such as Mg-Sc to broaden their application in the field of mechanical structures. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy and its preparation method. This solves the problem of insufficient overall mechanical properties in existing Mg-Sc alloys.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One objective of this invention is to provide a method for preparing a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy, comprising the following steps:

[0008] A Mg-35wt%Sc alloy mixture was prepared by using pure Sc and Mg-30wt%Sc alloy as raw materials.

[0009] The Mg-35wt%Sc alloy mixture was subjected to vacuum melting and homogenization solution treatment in sequence, and then hot extrusion treatment was carried out at 510℃ for 30 min and air-cooled to obtain Mg-35wt%Sc alloy rod sample with Ф=14mm.

[0010] The Mg-35wt%Sc alloy rod sample was cut into samples with a thickness of 2mm. The samples were then polished with 100#, 500#, 1000# and 2000# sandpaper until the alloy surface was bright. The samples were then heat-treated at 540℃ for 30min. The heat-treated samples were then cooled to obtain a Mg-Sc magnesium alloy with high strength and medium plasticity at room temperature.

[0011] This invention improves the overall mechanical properties of existing magnesium alloys by adding alloying rare earth element Sc, machining, and modifying heat treatment processes. Sc has a high maximum solid solubility in α-Mg (approximately 24.5 wt%). Introducing Sc atoms into the Mg matrix causes Mg lattice deformation, increasing the resistance to dislocations and slip during tensile deformation. Therefore, solid solution strengthening can improve the overall mechanical properties of magnesium alloys.

[0012] Furthermore, the pure Sc and Mg-30wt%Sc alloy needs to be pretreated before use. The specific treatment method is as follows: polish the alloy surface with 100#, 500#, 1000# and 2000# sandpaper in sequence until it is bright, clean it with anhydrous ethanol, and dry it.

[0013] Furthermore, the specific steps of the vacuum melting include: melting using a vacuum induction melting furnace, when the vacuum degree inside the furnace is evacuated to 5.0 × 10⁻⁶. -3 After Pa, pure argon gas at 0.05 MPa is introduced into the furnace. The power is turned on and the Mg-35wt%Sc melt is kept boiling for 3 minutes after the raw materials are completely melted. Then, it is kept at a current of 10A for 10 minutes. The resulting magnesium alloy is cooled to room temperature with the furnace and the cast Mg-35wt%Sc alloy is taken out.

[0014] Furthermore, the vacuum melting operation is repeated three times.

[0015] Furthermore, the extrusion ratio during the hot extrusion process is 11.6.

[0016] Furthermore, the specific steps of the homogenization solution treatment include: holding the as-cast Mg-35wt%Sc alloy obtained by vacuum melting at 610℃ for 12 hours, water quenching at room temperature, and polishing the obtained sample with 100#, 500#, 1000# and 2000# sandpaper until the alloy surface is bright to obtain Mg-35wt%Sc alloy.

[0017] Furthermore, the cooling process includes one of furnace cooling, air cooling, and room temperature water cooling.

[0018] The second objective of this invention is to provide a room-temperature high-strength and medium-plasticity Mg-Sc magnesium alloy prepared by the above-described preparation method.

[0019] Furthermore, the room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy comprises, by mass percentage, the following components: 35.0 wt% Sc, unavoidable impurities ≤0.02 wt% and balance Mg.

[0020] The third objective of this invention is to provide an application of a room-temperature high-strength and medium-plasticity Mg-Sc magnesium alloy in the field of mechanical structure.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] The Mg-35wt%Sc alloy prepared by this invention has a tensile yield strength (YS) of approximately 263.0-276.0 MPa, an ultimate tensile strength (UTS) of approximately 312.0-322.0 MPa, and an elongation of approximately 7.2-15.6%. Compared with existing magnesium alloys, the comprehensive mechanical properties have been greatly improved. Attached Figure Description

[0023] 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:

[0024] Figure 1 The XRD patterns of the Mg-35wt%Sc alloys prepared in Examples 1(a), 2(b), and 3(c) are shown.

[0025] Figure 2SEM images of the Mg-35wt%Sc alloys prepared in Examples 1(a), 2(b), and 3(c);

[0026] Figure 3 EBSD diagrams of Mg-35wt%Sc alloys prepared in Examples 1 (FC), 2 (AC), and 3 (WQ); where (a, d, g) are phase diagrams superimposed with α phase (green area) and β phase (red area); (b, e, h) α and (c, f, i) are IPF diagrams of β phase;

[0027] Figure 4 Grain size diagrams of Mg-35wt%Sc alloys prepared in Examples 1 (FC), 2 (AC), and 3 (WQ); wherein (a, d, g) are grain size diagrams of the α and β phases; (b, e, h) are grain size statistics of the α phase; and (c, f, i) are grain size statistics of the β phase.

[0028] Figure 5 Room temperature tensile stress-strain curves (a) and mechanical data (b) of Mg-35wt%Sc alloys prepared for Examples 1 (FC), 2 (AC), and 3 (WQ). Detailed Implementation

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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 readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0033] 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.

[0034] This invention provides a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy, comprising the following components by mass percentage (wt%): Sc: 35.0 wt%, unavoidable impurities ≤ 0.02 wt%, and the balance being Mg. The specific preparation method includes the following steps:

[0035] (1) Ingredients: Pure Sc (>99.99wt%, Hunan Rare Earth Metal Materials Research Institute, China) and Mg-30wt%Sc alloy (>99.00wt%, Hunan Rare Earth Metal Materials Research Institute, China) were used as raw materials. The required raw materials were cut with a wire cutting machine, and polished with 100#, 500#, 1000# and 2000# sandpaper in sequence until the alloy surface was bright to remove dirt and oxide layer from the surface of the raw materials. They were then cleaned with anhydrous ethanol (analytical grade 99.7%, Tianjin Fengchuan, the same below), dried at low temperature, and mixed into Mg-35wt%Sc alloy mixture according to the composition ratio.

[0036] (2) Melting: The raw materials are placed in a BN (boron nitride) crucible and then placed into a melting furnace. Melting is then carried out using a vacuum induction furnace. A mechanical pump is used to evacuate the furnace body until the vacuum level reaches 5.0 × 10⁻⁶. -1 After Pa, the vacuum level inside the cavity was evacuated to 5.0 × 10⁻⁶ using a diffusion pump. -3 Then, 0.05 MPa of pure argon gas is introduced into the furnace as a protective gas. The heating power supply of the induction melting instrument is turned on, and the current of the induction melting instrument is slowly increased until the raw materials are completely melted. The magnesium melt is kept boiling for 3 minutes. The current is maintained at 10 A for 10 minutes to ensure that the raw materials are mixed evenly. After the melting is completed, the instrument power is turned off. The furnace door is opened after the magnesium alloy has cooled to room temperature. The cast Mg-35wt%Sc alloy ingot is taken out. The cast Mg-35wt%Sc alloy ingot is put back into the induction melting furnace and melted three times in the same way to ensure uniform composition.

[0037] (3) Homogenization and solution treatment: The as-cast Mg-35wt%Sc alloy ingot obtained in step (2) is subjected to homogenization and solution treatment in an integrated muffle furnace. When the temperature in the muffle furnace rises to 610℃, the as-cast Mg-35wt%Sc alloy ingot is placed in the muffle furnace and kept at that temperature for 12 hours. Then, the Mg-35wt%Sc alloy is placed in distilled water at room temperature (about 25℃) for water quenching. The resulting Mg-35wt%Sc alloy is polished with 100#, 500#, 1000# and 2000# sandpaper in sequence until the alloy surface is bright to remove dirt and oxide layer from the surface of the raw material.

[0038] (4) Machining: The Mg-35wt%Sc alloy obtained in step (3) was subjected to hot extrusion. An 80T hydraulic press, an extrusion die (extrusion ratio of 11.6), a copper heating coil, and a temperature controller were used for the hot extrusion test. First, the Mg-35wt%Sc alloy after homogenization and solution treatment was machined into a size suitable for insertion into the sleeve. Graphite was applied to the magnesium alloy sample and the extrusion die. Then, the extrusion die, the pure copper heating coil, and the temperature controller were installed on the hydraulic press. The magnesium alloy sample was placed in the extrusion die, and the heating temperature was set to 510℃. The sample was held at this temperature for 30 minutes for extrusion to obtain a Mg-35wt%Sc alloy rod sample with a diameter of Ф=14mm. The rod sample was then air-cooled.

[0039] (5) Heat treatment and quenching process: The Mg-35wt%Sc alloy rod sample obtained in step (4) is cut into samples with a thickness of 2mm using a wire cutting machine. These samples are polished with 100#, 500#, 1000# and 2000# sandpaper until the alloy surface is bright to remove the dirt and oxide layer on the surface of the raw material. The 2mm thick sample is heat treated at 540℃ for 30min in a muffle furnace. The heat-treated samples are subjected to different heat treatment cooling methods to obtain Mg-35wt%Sc alloys with different microstructures. These alloys are polished with 100#, 500#, 1000#, 2000# and 3000# sandpaper until the alloy surface is bright to obtain a Mg-Sc magnesium alloy with high strength and medium plasticity at room temperature.

[0040] The heat treatment cooling method includes one of furnace cooling (FC), air cooling (AC), and room temperature water cooling (WQ).

[0041] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

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

[0043] Example 1

[0044] A room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy, comprising, by weight percentage (wt%), the following components: Sc: 35.0 wt%, unavoidable impurities ≤ 0.02 wt%, and the balance being Mg. The specific preparation method includes the following steps:

[0045] (1) Batching: Cut the raw materials pure Sc and Mg-30wt%Sc alloy into pieces using a wire cutting machine, and polish them with 100#, 500#, 1000# and 2000# sandpaper in sequence until the alloy surface is bright. Then clean them with anhydrous ethanol, dry them, and mix them into Mg-35wt%Sc alloy mixture according to the composition ratio.

[0046] (2) Melting: After the raw materials in step (1) are proportioned, they are placed into a BN crucible and then into a melting furnace. A mechanical pump is used to evacuate the furnace body until the vacuum level inside the furnace reaches 5.0 × 10⁻⁶. -1 After Pa, the vacuum level inside the cavity was evacuated to 5.0 × 10⁻⁶ using a diffusion pump. -3 Pa, then charge the furnace with 0.05 MPa of pure argon gas as a protective gas, turn on the heating power of the induction melting instrument, slowly increase the current of the induction melting instrument until the raw material is completely melted, and keep the magnesium melt boiling for 3 minutes; keep it at a current of 10 A for 10 minutes; after melting is completed, turn off the instrument power, wait for the magnesium alloy to cool to room temperature with the furnace before opening the furnace door and taking out the cast Mg-35wt%Sc alloy ingot; put the cast Mg-35wt%Sc alloy ingot back into the induction melting furnace and melt it three times in the same way;

[0047] (3) Homogenization solution treatment: When the temperature inside the muffle furnace rises to 610℃, the cast Mg-35wt%Sc alloy ingot obtained in step (2) is placed in the muffle furnace and kept at the temperature for 12 hours. Then, the Mg-35wt%Sc alloy is placed in distilled water at room temperature (about 25℃) for water quenching. The obtained Mg-35wt%Sc alloy is polished with 100#, 500#, 1000# and 2000# sandpaper in sequence until the alloy surface is bright.

[0048] (4) Machining: A hot extrusion test was conducted using an 80T hydraulic press, an extrusion die (extrusion ratio of 11.6), a copper heating coil, and a temperature controller. First, the Mg-35wt%Sc alloy obtained in step (3) was machined into a size suitable for insertion into the sleeve. Graphite was applied to the magnesium alloy sample and the extrusion die. Then, the extrusion die, the pure copper heating coil, and the temperature controller were installed on the hydraulic press. The magnesium alloy sample was placed in the extrusion die, and the heating temperature was set to 510℃. The sample was held at this temperature for 30 minutes and then extruded to obtain a Mg-35wt%Sc alloy rod sample with a diameter of Ф=14mm. The rod sample was then air-cooled.

[0049] (5) Heat treatment and quenching process: The Mg-35wt%Sc alloy rod sample obtained in step (4) is cut into a sample with a thickness of 2mm using a wire cutting machine. Then, it is polished with 100#, 500#, 1000# and 2000# sandpaper in sequence until the alloy surface is bright. The sample with a thickness of 2mm is then heat-treated in a muffle furnace at 540℃ for 30min. The heat-treated sample is cooled by furnace cooling (FC). Finally, it is polished with 100#, 500#, 1000#, 2000# and 3000# sandpaper in sequence until the alloy surface is bright, thus obtaining a Mg-Sc magnesium alloy with high strength and medium plasticity at room temperature.

[0050] Example 2

[0051] Similar to Example 1, except that in step (5), the method of cooling the heat-treated sample is replaced by air cooling (AC).

[0052] Example 3

[0053] Same as Example 1, except that in step (5), the method of cooling the heat-treated sample is replaced by room temperature water cooling (WQ).

[0054] Performance testing

[0055] The phase composition of the Mg-35wt%Sc alloys prepared in Examples 1-3 was analyzed by X-ray diffraction, and the results are as follows: Figure 1 As shown. Figure 1 The results showed that the Mg-35wt%Sc alloys prepared in Examples 1-3 all contained only α and β phases, with the least β phase in Example 1 (FC), followed by the β phase in Example 2 (AC), and the most β phase in Example 3 (WQ). Based on the positions of the diffraction peaks, the lattice constant of the α phase was obtained: a α =b α =0.328nm, c α =0.523nm, lattice constant of the β phase: a β =b β =c β =0.361nm.

[0056] The Mg-35wt%Sc alloys prepared in Examples 1-3 were observed under a scanning electron microscope, and the results are as follows: Figure 2 As shown. Figure 2 The results show that in the Mg-35wt%Sc alloys prepared in Examples 1 (FC), 2 (AC), and 3 (WQ), the β phase exhibits an irregular morphological distribution, and the β phase in all samples is aggregated at the α phase boundary. With the increase of the heat treatment cooling rate, the content and size of the β phase in the samples gradually increase.

[0057] The Mg-35wt%Sc alloys prepared in Examples 1-3 were observed by electron backscatter diffraction (EBSD), and the results are as follows: Figure 3 As shown. Figure 3 The results show that the β phase in the Mg-35wt%Sc alloys prepared in Examples 1-3 is mainly distributed at the phase boundary of the α phase. The volume fractions of the β phase in the samples of Example 1 (FC), Example 2 (AC) and Example 3 (WQ) are 1.3%, 4.9% and 12.8%, respectively.

[0058] The Mg-35wt%Sc alloys prepared in Examples 1-3 were subjected to grain size analysis of the α and β phases based on EBSD data. The results are as follows: Figure 4 As shown. Figure 4 The results show that the average grain size of the α and β phases in the Mg-35wt%Sc alloys prepared in Examples 1-3 varies with the cooling rate of heat treatment. The average grain size of the α phase in the samples of Example 1 (FC), Example 2 (AC), and Example 3 (WQ) is approximately 33.3 μm, 32.9 μm, and 31.6 μm, respectively; while the average grain size of the β phase in the samples of Example 1 (FC), Example 2 (AC), and Example 3 (WQ) is approximately 2.2 μm, 4.1 μm, and 9.5 μm, respectively.

[0059] The Mg-35wt%Sc alloys prepared in Examples 1-3 were subjected to room temperature tensile mechanical property tests. The room temperature tensile stress-strain curves and mechanical data are as follows: Figure 5 As shown. Figure 5 The results showed that the Mg-35wt%Sc alloy prepared in Example 1 (FC) had a YS of 263.0 MPa, a UTS of 322.0 MPa, and an elongation of 15.6%; the Mg-35wt%Sc alloy prepared in Example 2 (AC) had a YS of 263.3 MPa, a UTS of 312.0 MPa, and an elongation of 11.7%; and the Mg-35wt%Sc alloy prepared in Example 3 (WQ) had a YS of 276.0 MPa, a UTS of 313.0 MPa, and an elongation of 7.2%.

[0060] 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. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy, characterized in that, Includes the following steps: A Mg-35wt%Sc alloy mixture was prepared by using pure Sc and Mg-30wt%Sc alloy as raw materials. The Mg-35wt%Sc alloy mixture was subjected to vacuum melting and homogenization solution treatment in sequence, and then hot extrusion treatment was carried out at 510℃ for 30 min and air-cooled to obtain Mg-35wt%Sc alloy rod sample with Ф=14mm. The Mg-35wt%Sc alloy rod sample was cut into samples with a thickness of 2mm. Then, the samples were polished with 100#, 500#, 1000# and 2000# sandpaper until the alloy surface was bright. Then, the samples were heat-treated at 540℃ for 30min. The heat-treated samples were cooled to obtain a Mg-Sc magnesium alloy with high strength and medium plasticity at room temperature. The specific steps of the vacuum melting include: melting using a vacuum induction melting furnace, and when the vacuum level inside the furnace is evacuated to 5.0 × 10⁻⁶... -3 After Pa, pure argon gas at 0.05 MPa was introduced into the furnace. The power was turned on and the Mg-35wt%Sc melt was kept boiling for 3 minutes after the raw materials were completely melted. Then, it was kept at a current of 10A for 10 minutes. The resulting magnesium alloy was cooled to room temperature with the furnace and the cast Mg-35wt%Sc alloy was taken out. The specific steps of the homogenization solution treatment include: holding the as-cast Mg-35wt%Sc alloy obtained by vacuum melting at 610℃ for 12 hours, water quenching at room temperature, and polishing the obtained sample with 100#, 500#, 1000# and 2000# sandpaper until the alloy surface is bright to obtain Mg-35wt%Sc alloy.

2. The method for preparing a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy according to claim 1, characterized in that, The pure Sc and Mg-30wt%Sc alloys need to be pretreated before use. The specific treatment method is as follows: polish the alloy surface with 100#, 500#, 1000# and 2000# sandpaper in sequence until it is bright, clean it with anhydrous ethanol and dry it.

3. The method for preparing a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy according to claim 1, characterized in that, The vacuum melting process was repeated three times.

4. The method for preparing a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy according to claim 1, characterized in that, The extrusion ratio during the hot extrusion process is 11.

6.

5. The method for preparing a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy according to claim 1, characterized in that, The cooling process includes one of the following: furnace cooling, air cooling, and room temperature water cooling.

6. A room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy prepared by the preparation method according to any one of claims 1-5.

7. The room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy according to claim 6, characterized in that, The composition comprises, by mass percentage, 35.0 wt% Sc, ≤0.02 wt% unavoidable impurities, and balance Mg.

8. The application of a room-temperature high-strength and medium-ductility Mg-Sc magnesium alloy as described in any one of claims 6-7 in the field of mechanical structures.

Images