Preparation method of high-performance magnesium alloy plate containing ytterbium

Abstract

The application discloses a preparation method of a high-performance magnesium alloy plate containing ytterbium, and has the chemical components as follows in percentage by mass: 5.8-6.0% of zinc, 1.8-2.0% of ytterbium, 0.6% of zirconium, and the rest of magnesium; the preparation method comprises smelting, solid solution and hot rolling. The magnesium alloy plate is added with proper rare earth ytterbium, and after common hot rolling, the magnesium alloy plate forms uniform and refined microstructure and special non-base surface weak texture, greatly improves the strength and plasticity of the plate, and has the characteristics of low cost, short process and high performance.

Description

Technical Field

[0001] This invention relates to the field of magnesium alloy materials technology, and in particular to a method for preparing high-performance magnesium alloy plates containing the rare earth element ytterbium. Background Technology

[0002] Magnesium alloys possess advantages such as lightweight, environmental friendliness, high specific strength, and high specific stiffness. Parts and products made from magnesium alloy sheets can be applied in sectors vital to national economy and people's livelihood, such as automobiles, aviation, aerospace, 5G communications, and 3C electronics, where lightweighting is crucial. However, due to insufficient absolute strength, poor formability, and the tendency of low-symmetry crystal structures to form textures and mechanical anisotropy, the large-scale application of magnesium alloys in these fields is severely limited. Therefore, there is an urgent need to obtain high-performance magnesium alloy sheets with good strength-plasticity matching and mechanical isotropy through the optimization of alloying elements and the design of manufacturing processes.

[0003] Studies have shown that adding alloying elements such as aluminum, zinc, and manganese to magnesium alloys, coupled with hot rolling deformation, can effectively improve the strength of magnesium alloy sheets. This is because hot rolling deformation can compact casting defects, promote dynamic recrystallization, and refine deformed grains, thereby inducing a significant fine-grain strengthening effect. Simultaneously, the dynamically precipitated alloying element-containing second phase can pin dislocations and inhibit dislocation slip. Hot rolling forms a strong basal plane texture with the c-axis parallel to the sheet's normal direction, further enhancing the sheet's strength along the rolling direction. Although these factors effectively improve strength, they negatively impact the plasticity of the matrix, and the formation of the strong basal plane texture also leads to anisotropy in the sheet's mechanical properties, which is detrimental to subsequent forming processes such as stamping. Recent research indicates that by rationally selecting rare earth elements and their amounts, combined with hot deformation processes, a weak texture can be formed in deformed samples with a relatively complete degree of recrystallization. This relatively discrete grain orientation characteristic can promote more efficient basal plane slip in subsequent deformation of the alloy, thereby achieving high hardening capacity and improved plasticity. However, based on existing technologies, it is often difficult to simultaneously achieve both strength and ductility in wrought magnesium alloys. Patent 201210461370.6 discloses "a low-Gd content, high-ductility magnesium alloy sheet and its hot rolling process," reporting a ductility as high as 50%, but its maximum tensile strength is only 253 MPa. Similarly, patent 202110253005.5 discloses a method for preparing a "double-layer sandwich" rolled high-strength rare-earth magnesium alloy, reporting a tensile strength as high as 548 MPa, but its ductility is only 2%. It is evident that the difficulty in balancing strength, ductility, and mechanical isotropy is a common problem in the rolling of wrought magnesium alloys, severely restricting the large-scale application of magnesium alloy sheets.

[0004] In view of this, the present invention discloses a method for preparing high-performance magnesium alloy sheets containing ytterbium. This technology, through the optimization of alloy composition and content combined with a hot rolling deformation process, yields wrought magnesium alloy sheets possessing high strength, high plasticity, and low mechanical anisotropy. It features low cost, short process, and high performance, effectively improving the comprehensive mechanical properties of traditional magnesium alloy sheets. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing deformed magnesium alloy sheets, such as uneven strength and plasticity and large anisotropy in mechanical properties, and to provide a method for preparing high-performance magnesium alloy sheets. The technical problem to be solved is that existing hot-rolled magnesium alloy sheets cannot simultaneously achieve high strength and high plasticity, and exhibit large mechanical anisotropy, resulting in insufficient strength or defects such as indentations, cracks, and lugs in parts after subsequent stamping processing, affecting the service safety and stability of magnesium alloy sheet parts. This invention effectively improves the comprehensive mechanical properties of magnesium alloy sheets by optimizing rare earth alloying elements and their addition amounts, coupled with targeted preparation process design. The room temperature tensile mechanical properties of the ytterbium-containing high-performance magnesium alloy sheet invented are as follows: elongation 10-15% along the rolling direction, yield strength 230-280 MPa, and tensile strength 350-380 MPa; and room temperature tensile mechanical properties along the transverse direction: elongation 15-20%, yield strength 210-260 MPa, and tensile strength 320-350 MPa. The anisotropy index of the yield strength of the sheet after hot rolling is less than or equal to 8%. This invention features low cost, short process, and high performance, and can effectively improve the comprehensive mechanical properties of traditional magnesium alloy sheets.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention optimizes the design of alloying elements and their contents, and utilizes a reasonable melting and casting process to fully leverage the purifying effects of Zr and Yb on the magnesium alloy melt, as well as the strong compositional undercooling effect of Zr. This results in uniform, equiaxed, and refined initial as-cast grains. Further, high-temperature solid solution fully dissolves the second phase and inhibits grain growth, followed by cyclic hot rolling and annealing at 300 °C. The purpose of hot rolling is to fully activate dislocations in the ytterbium-containing magnesium alloy at a lower rolling temperature, especially the non-basal dislocations formed by a sufficient amount of 2.0 wt.% Yb solid solution, thereby stimulating continuous dynamic recrystallization, driving subgrain rotation and orientation dispersion, reducing the area ratio of deformed grains, and suppressing the formation of strong basal texture. The subsequent annealing promotes dislocation recovery, accelerates the recrystallization process, reduces dislocation density, and inhibits dislocation saturation, effectively restoring the work hardening capacity and resistance to edge cracking instability of the sheet metal, preparing it for the next hot rolling cycle. Through repeated cycles of various dislocation configurations on and off the basal and non-basal planes, as well as annealing recovery, a uniform and refined grain structure and second-phase distribution are achieved. A high recrystallization ratio and a unique weak texture with continuous basal plane deflections of ±30°~45° and ±70°~85° along the rolling direction and transverse direction, respectively, allow for efficient basal plane slippage along all deformation directions during subsequent pressure processing, effectively improving the sheet's mechanical isotropy and work hardening capacity. Simultaneously, the high density of the second phase and grain boundaries provides sufficient strength, comprehensively enhancing the balance between the sheet's strength, plasticity, and mechanical isotropy.

[0008] The specific technical solution is as follows:

[0009] A method for preparing a high-performance magnesium alloy sheet containing ytterbium, characterized in that: the mass percentage of the alloy composition is: Zn content 5.8~6.0%, Yb content 1.8~2.0%, Zr content 0.6%, with the balance being Mg and unavoidable impurities; the preparation steps are alloy melting → solution treatment → hot rolling → annealing → hot rolling…, cyclic annealing and hot rolling until the preset rolling thickness is reached; the alloy is rolled at 300 ℃, ensuring that the reduction in each pass is 5~8% of the total reduction, and the alloy is reheated at 300 ℃ for 15~20 minutes between each two adjacent hot rolling passes. Annealing is performed at min, with a total rolling amount of 70-80% of the original material thickness. The final alloy recrystallization ratio is 75-90%, forming a weak texture with continuous deflection of ±30°~±45° and ±70°~±85° along the rolling direction and transverse direction, respectively. The room temperature tensile mechanical properties of the alloy along the rolling direction are: elongation 10-15%, yield strength 230-280 MPa, and tensile strength 350-380 MPa. The room temperature tensile mechanical properties along the transverse direction are: elongation 15-20%, yield strength 210-260 MPa, and tensile strength 320-350 MPa. The planar anisotropy index of the yield strength of the hot-rolled plate is less than or equal to 8%.

[0010] Furthermore, a method for preparing a high-performance magnesium alloy sheet containing ytterbium is characterized by the following: after the magnesium alloy is melted, the as-cast microstructure consists of uniform equiaxed grains with an average grain size of 30-35 μm. The grain boundaries are discontinuously distributed with Mg–Zn phases of 0.2-0.5 μm diameter, Mg–Zn–Yb phases of 0.5-1.5 μm diameter, and 1-2 μm incompletely dissolved Yb and Zr particles. After solution treatment, the microstructure does not undergo overheating, the equiaxed grains slightly grow, with an average grain size of 35-40 μm, and the grain boundaries are smooth but a small amount of the second phase is not fully dissolved back into the matrix, with an average size of 0.5-1 μm. After cyclic hot rolling annealing, the grains recrystallize and become refined, with a recrystallized grain size of 5-8 μm, and a large number of submicron-sized, approximately spherical Mg-Zn-Yb phases and short rod-shaped Mg-Zn phases distributed within the grains.

[0011] Furthermore, a method for preparing a high-performance magnesium alloy sheet containing ytterbium is characterized by comprising the following preparation steps:

[0012] 1) Alloy smelting: Magnesium ingots are heated and melted in a resistance heating furnace under SF6 + CO2 gas protection. Then, Mg-Zr master alloy is added at 750~760 ℃ to make the Zr content 0.6% of the final smelted alloy by mass percentage. Stirring is carried out for 1~3 min under solvent protection to aid melting. Then, Mg-Yb master alloy is added at 750~760 ℃ to make the Yb content 1.8~2.0% of the final smelted alloy by mass percentage. Finally, pure zinc ingots are added at 720~730 ℃ to make the Zn content 5.8~6.0% of the final smelted alloy by mass percentage. Stirring is carried out for 1~3 min to aid melting. The mixture is held at 700~720 ℃ for 8~10 min and a covering agent is added to settle the slag. After standing at 700~720 ℃, the slag is removed and the ingots are cast. The ingots are then immediately water quenched.

[0013] 2) Solution treatment: Place the above-mentioned ingots in a gas-protected heat treatment furnace and hold them at 400~420 ℃ for 45~48 h, then immediately cool them to room temperature with water;

[0014] 3) Cyclic hot rolling and annealing: The solution-treated plate is held at 300 ℃ for 20~30 min, followed by cyclic hot rolling and annealing. The roll speed is 5~10 m / min, the temperature of the upper and lower rolls is 150~200 ℃, and the temperature difference between the upper and lower rolls is ±5~6 °C. After rolling, the plate is immediately cooled to room temperature with water.

[0015] Compared to existing magnesium alloy materials, the advantages of this material and its preparation method are as follows:

[0016] 1) This invention enables magnesium alloy sheets to simultaneously activate multiple deformation coordination mechanisms such as basal plane, non-basal plane and twinning during the deformation process by adding trace amounts of Yb and using low-temperature hot rolling process. This promotes the formation and rotation of subgrains, inhibits the formation of strong basal plane texture dominated by basal plane slip, and overcomes the formation of microstructure characteristics that are detrimental to plasticity and mechanical isotropy from the source.

[0017] 2) Adding an isothermal annealing process between two consecutive hot rolling processes can effectively drive dislocation recovery and recrystallization, suppress the lack of work hardening ability and edge crack instability caused by dislocation saturation, stabilize the microstructure and improve the deformation processing capability, and provide microstructure guarantee for the introduction of high-density dislocations and the formation of subgrains in the next hot rolling process.

[0018] 3) During cyclic annealing and hot rolling, the grains are subjected to the cyclic action of high-density dislocation accumulation and recovery, causing them to rotate under various random dislocation configurations. This results in the alloy sheet forming a continuous, large-angle non-basal plane weak texture characteristic along the rolling direction and transverse direction, effectively improving plastic processing capability and reducing mechanical anisotropy. At the same time, cyclic annealing and hot rolling promotes the full and uniform refinement of grains and precipitates / second phases. Without sacrificing plasticity, the matrix is ​​effectively strengthened through fine grain strengthening and second phase dispersion strengthening, achieving a simultaneous improvement in strength, plasticity, and isotropic mechanical properties.

[0019] 4) This invention selects trace amounts of Yb and Zr, along with a small amount of Zn, as the main alloying design, resulting in low cost, readily available raw materials, and significant effects. Compared with other magnesium alloy processing technologies, this preparation process is simple to operate, energy-saving, uses conventional equipment, and is low in cost. Compared with complex deformation processes, it has better prospects for widespread application. Attached Figure Description

[0020] Figure 1 The images show (a) as-cast state, (b) rolled state, and (c) second-phase point scan, element surface scan, and (0001) pole figure of the Mg–6.0 Zn–2.0 Yb–0.6 Zr alloy prepared using the technology described in this application.

[0021] Figure 2 The images show (a) as-cast state, (b) rolled state, and (c) second-phase point scan, element surface scan, and (0001) pole figure of the Mg–5.8 Zn–1.8 Yb–0.6 Zr alloy prepared using the technology described in this application. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, it should not be construed as a limitation on the scope of protection of the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] A method for preparing a high-performance magnesium alloy sheet containing ytterbium, characterized in that: the mass percentage of the alloy composition is: Zn 6.0%, Yb 2.0%, Zr 0.6%, with the balance being Mg and unavoidable impurities; the preparation steps are alloy melting → solution treatment → hot rolling → annealing → hot rolling…, cyclic annealing and hot rolling until the preset rolling thickness is reached; the alloy is rolled at 300 ℃, ensuring that the reduction in each pass is 8% of the total reduction, and annealing is performed at 300 ℃ for 20 min between every two adjacent hot rolling passes, with the total rolling amount being 80% of the original thickness of the material, and the final alloy recrystallization ratio is ~90%, forming a weak texture with continuous deflection of ±45° and ±85° along the rolling direction and transverse direction, respectively; the room temperature tensile mechanical properties of the alloy along the rolling direction are: elongation ~10%, yield strength ~280 MPa, tensile strength ~380 MPa. MPa; the room temperature tensile mechanical properties in the transverse direction are: elongation ~15%, yield strength ~260 MPa, tensile strength ~350 MPa; the plane anisotropy index of the yield strength of the hot-rolled plate is less than 8%, and the relevant microstructure characteristics are as follows: Figure 1 As shown.

[0025] Furthermore, a method for preparing a high-performance magnesium alloy sheet containing ytterbium is characterized by the following: after the magnesium alloy is melted, the as-cast microstructure consists of uniform equiaxed grains with an average grain size of ~30 μm. Discontinuous distributions of Mg–Zn phases with a diameter of ~0.5 μm, Mg–Zn–Yb phases with a diameter of ~1.5 μm, and incompletely dissolved Yb and Zr particles with a diameter of ~2 μm are present at the grain boundaries. After solution treatment, the microstructure does not undergo overheating, the equiaxed grains slightly grow, with an average grain size of ~35 μm, and the grain boundaries are smooth but a small amount of the second phase is not fully dissolved back into the matrix, with an average size of ~1 μm. After cyclic hot rolling annealing, the grains recrystallize and become refined, with a recrystallized grain size of ~5 μm, and a large number of submicron-sized, approximately spherical Mg-Zn-Yb phases and short rod-shaped Mg-Zn phases are distributed within the grains.

[0026] Furthermore, a method for preparing a high-performance magnesium alloy sheet containing ytterbium is characterized by comprising the following preparation steps:

[0027] 1) Alloy smelting: Magnesium ingots are heated and melted in a resistance heating furnace under SF6 + CO2 gas protection. Then, Mg-Zr master alloy with a Zr content of 0.6% of the final smelting alloy design mass percentage is added at 760 ℃. The mixture is stirred for ~3 min under solvent protection to aid melting. Then, Mg-Yb master alloy with a Yb content of 2.0% of the final smelting alloy design mass percentage is added at 760 ℃. Finally, pure zinc ingots with a Zn content of 6.0% of the final smelting alloy design mass percentage are added at 730 ℃. The mixture is stirred for 3 min to aid melting. The mixture is held at 720 ℃ for 10 min and a covering agent is added to settle the slag. After standing at 720 ℃, the slag is removed and the ingots are cast. The ingots are then immediately water quenched.

[0028] 2) Solution treatment: Place the above-mentioned ingot in a gas-protected heat treatment furnace, hold it at 420 ℃ for 48 h, and then immediately water cool it to room temperature;

[0029] 3) Cyclic hot rolling and annealing: The solution-treated plate is held at 300 ℃ for 30 min, followed by cyclic hot rolling and annealing. The roll speed is 10 m / min, the temperature of the upper and lower rolls is 200 ℃, and the temperature difference between the upper and lower rolls is ±5 °C. After rolling, the plate is immediately cooled to room temperature with water.

[0030] Example 2

[0031] A method for preparing a high-performance magnesium alloy sheet containing ytterbium, characterized in that: the mass percentage of the alloy composition is: Zn 5.8%, Yb 1.8%, Zr 0.6%, with the balance being Mg and unavoidable impurities; the preparation steps are alloy melting → solution treatment → hot rolling → annealing → hot rolling…, cyclic annealing and hot rolling until the preset rolling thickness is reached; the alloy is rolled at 300 ℃, ensuring that the reduction in each pass is 5% of the total reduction, and annealing is performed at 300 ℃ for 15 min between every two adjacent hot rolling passes, with the total rolling amount being 70% of the original thickness of the material, and the final alloy recrystallization ratio is ~75%, forming a weak texture with continuous deflection of ±30° and ±70° along the rolling direction and transverse direction, respectively; the room temperature tensile mechanical properties of the alloy along the rolling direction are: elongation ~15%, yield strength ~230 MPa, tensile strength ~350 MPa. MPa; the room temperature tensile mechanical properties in the transverse direction are: elongation ~20%, yield strength ~210 MPa, tensile strength ~320 MPa; the plane anisotropy index of the yield strength of the hot-rolled plate is less than 8%, and the relevant microstructure characteristics are as follows: Figure 2 As shown.

[0032] Furthermore, a method for preparing a high-performance magnesium alloy sheet containing ytterbium is characterized by the following: after the magnesium alloy is melted, the as-cast microstructure consists of uniform equiaxed grains with an average grain size of ~35 μm. Discontinuous distributions of Mg–Zn phases with a diameter of ~0.2 μm, Mg–Zn–Yb phases with a diameter of ~0.5 μm, and incompletely dissolved Yb and Zr particles with a diameter of ~1 μm are present at the grain boundaries. After solution treatment, the microstructure does not undergo overheating, the equiaxed grains slightly grow, with an average grain size of ~40 μm, and the grain boundaries are smooth but a small amount of the second phase is not fully dissolved back into the matrix, with an average size of ~0.5 μm. After cyclic hot rolling annealing, the grains recrystallize and become refined, with a recrystallized grain size of ~8 μm, and a large number of submicron-sized, approximately spherical Mg-Zn-Yb phases and short rod-shaped Mg-Zn phases are distributed within the grains.

[0033] The method for preparing a high-performance magnesium alloy sheet containing ytterbium is characterized by comprising the following preparation steps:

[0034] 1) Alloy smelting: Magnesium ingots are heated and melted in a resistance heating furnace under SF6 + CO2 gas protection. Then, Mg-Zr master alloy with a Zr content of 0.6% of the final smelting alloy design mass percentage is added at 750 ℃. The mixture is stirred for 1 min under solvent protection to aid melting. Then, Mg-Yb master alloy with a Yb content of 1.8% of the final smelting alloy design mass percentage is added at 750 ℃. Finally, pure zinc ingots with a Zn content of 5.8% of the final smelting alloy design mass percentage are added at 720 ℃. The mixture is stirred for 1 min to aid melting. The mixture is held at 700 ℃ for 8 min and a covering agent is added to remove slag. After standing at 700 ℃, the slag is removed and the ingots are cast. The ingots are then immediately water quenched.

[0035] 2) Solution treatment: Place the above-mentioned ingot in a gas-protected heat treatment furnace, hold it at 400 ℃ for 45 h, and then immediately water cool it to room temperature;

[0036] 3) Cyclic hot rolling and annealing: The solution-treated plate is held at 300 ℃ for 20 min, followed by cyclic hot rolling and annealing. The roll speed is 5 m / min, the temperature of the upper and lower rolls is 150 ℃, and the temperature difference between the upper and lower rolls is ±6 °C. After rolling, the plate is immediately cooled to room temperature with water.

[0037] Example 3

[0038] A method for preparing a high-performance magnesium alloy sheet containing ytterbium, characterized in that: the mass percentage of the alloy composition is: Zn 6.0%, Yb 1.8%, Zr 0.6%, with the balance being Mg and unavoidable impurities; the preparation steps are alloy melting → solution treatment → hot rolling → annealing → hot rolling…, cyclic annealing and hot rolling until the preset rolling thickness is reached; the alloy is rolled at 300 ℃, ensuring that the reduction in each pass is 7% of the total reduction, and annealing is performed at 300 ℃ for 18 min between every two adjacent hot rolling passes, with the total rolling amount being 75% of the original material thickness, and the final alloy recrystallization ratio is ~85%, forming a weak texture with continuous deflection of ±40° and ±80° along the rolling direction and transverse direction, respectively; the room temperature tensile mechanical properties of the alloy along the rolling direction are: elongation 14%, yield strength ~263 MPa, tensile strength ~355 MPa. MPa; the room temperature tensile mechanical properties in the transverse direction are: elongation ~18%, yield strength ~233 MPa, tensile strength ~325 MPa; the plane anisotropy index of the yield strength of the hot-rolled plate is less than 8%.

[0039] Furthermore, a method for preparing a high-performance magnesium alloy sheet containing ytterbium is characterized by the following: after the magnesium alloy is melted, the as-cast microstructure consists of uniform equiaxed grains with an average grain size of ~32 μm. Discontinuous distributions at the grain boundaries include Mg–Zn phases with a diameter of ~0.4 μm, Mg–Zn–Yb phases with a diameter of ~1.0 μm, and incompletely dissolved Yb and Zr particles with a diameter of ~1.3 μm. After solution treatment, the microstructure does not undergo overheating, the equiaxed grains slightly grow, with an average grain size of ~36 μm, and the grain boundaries are smooth but contain a small amount of second phase that has not fully dissolved back into the matrix, with an average size of ~0.7 μm. After cyclic hot rolling annealing, the grains recrystallize and become refined, with a recrystallized grain size of ~7 μm, and a large number of submicron-sized, approximately spherical Mg-Zn-Yb phases and short rod-shaped Mg-Zn phases distributed within the grains.

[0040] Furthermore, a method for preparing a high-performance magnesium alloy sheet containing ytterbium is characterized by comprising the following preparation steps:

[0041] 1) Alloy smelting: Magnesium ingots are heated and melted in a resistance heating furnace under SF6 + CO2 gas protection. Then, Mg-Zr master alloy with a Zr content of 0.6% of the final smelting alloy design mass percentage is added at 760 ℃. The mixture is stirred for 2 min under solvent protection to aid melting. Then, Mg-Yb master alloy with a Yb content of 1.8% of the final smelting alloy design mass percentage is added at 750 ℃. Finally, pure zinc ingots with a Zn content of 6.0% of the final smelting alloy design mass percentage are added at 730 ℃. The mixture is stirred for 2 min to aid melting. The mixture is held at 710 ℃ for 9 min and a covering agent is added to settle the slag. After standing at 710 ℃, the slag is removed and the ingots are cast. The ingots are then immediately water quenched.

[0042] 2) Solution treatment: Place the above-mentioned ingot in a gas-protected heat treatment furnace, hold it at 410 ℃ for 46 h, and then immediately water cool it to room temperature;

[0043] 3) Cyclic hot rolling and annealing: The solution-treated plate is held at 300 ℃ for 25 min, followed by cyclic hot rolling and annealing. The roll speed is 8 m / min, the temperature of the upper and lower rolls is 180 ℃, and the temperature difference between the upper and lower rolls is ±5 °C. After rolling, the plate is immediately cooled to room temperature with water.

[0044] Finally, it should be noted that the above embodiments are only used to more clearly illustrate the working principle and process of the present invention and do not limit the present invention. The present invention can also be applied to hot-rolled magnesium alloys with other Mg–Zn–Yb–Zr contents as defined in this application; the processing principle and steps are no different from the above examples, so there is no need to repeat the examples. The creative contribution of the present invention to the prior art lies in obtaining high-performance wrought magnesium alloy sheets with the above-mentioned properties through optimized alloy element design, supplemented by targeted melting, solution treatment, cyclic hot rolling, and annealing processes. This effectively expands the application fields of magnesium alloys, develops the potential of alloy performance, and has the advantages of excellent comprehensive performance, short process, and high efficiency, with very significant beneficial effects.

Claims

1. A method for preparing a high-performance magnesium alloy sheet containing ytterbium, characterized in that: The alloy composition by mass percentage is as follows: Zn content 5.8-6.0%, Yb content 1.8-2.0%, Zr content 0.6%, with the balance being Mg and unavoidable impurities. The preparation steps are alloy melting → solution treatment → hot rolling → annealing → hot rolling..., cyclic annealing and hot rolling until the preset rolling thickness is reached. The alloy is rolled at 300 ℃, ensuring that the reduction in each pass is 5-8% of the total reduction. Annealing is performed at 300 ℃ for 15-20 min between every two adjacent hot rolling passes. The total rolling amount is 70-80% of the original material thickness. The final alloy recrystallization ratio is 75-90%, forming a weak texture with continuous deflection of the basal plane along the rolling direction and transverse direction, with continuous deflection of 30°-45° in the rolling direction and 70°-85° in the transverse direction. The room temperature tensile mechanical properties of the alloy along the rolling direction are: elongation 10-15%, yield strength 230-280 Nm. MPa, tensile strength 350~380 MPa; room temperature tensile mechanical properties in the transverse direction: elongation 15~20%, yield strength 210~260 MPa, tensile strength 320~350 MPa; the plane anisotropy index of the yield strength of the hot-rolled plate is less than or equal to 8%.

2. The method for preparing a high-performance magnesium alloy sheet containing ytterbium according to claim 1, characterized in that: The as-cast microstructure of the magnesium alloy after melting is a uniform equiaxed grain with an average grain size of 30-35 μm. Discontinuous distributions of 0.2-0.5 μm diameter Mg-Zn phase, 0.5-1.5 μm diameter Mg-Zn-Yb phase, and 1-2 μm incompletely dissolved Yb and Zr particles are present at the grain boundaries. After solution treatment, the microstructure does not undergo overheating, the equiaxed grains grow slightly, with an average grain size of 35-40 μm, and the grain boundaries are smooth, but a small amount of the second phase is not fully dissolved back into the matrix, with an average size of 0.5-1 μm. After cyclic hot rolling annealing, the grains recrystallize and become refined, with a recrystallized grain size of 5-8 μm. Numerous submicron-sized, nearly spherical Mg-Zn-Yb phases and short rod-shaped Mg-Zn phases are distributed within the grains.

3. A method for preparing a ytterbium-containing high-performance magnesium alloy sheet according to any one of claims 1-2, characterized in that: The preparation steps include the following: 1) Alloy smelting: Magnesium ingots are heated and melted in a resistance heating furnace under SF6 + CO2 gas protection. Then, Mg-Zr master alloy is added at 750~760 ℃ to make the Zr content 0.6% of the final smelted alloy by mass percentage. Stirring is carried out for 1~3 min under flux protection to aid melting. Then, Mg-Yb master alloy is added at 750~760 ℃ to make the Yb content 1.8~2.0% of the final smelted alloy by mass percentage. Finally, pure zinc ingots are added at 720~730 ℃ to make the Zn content 5.8~6.0% of the final smelted alloy by mass percentage. Stirring is carried out for 1~3 min to aid melting. The mixture is held at 700~720 ℃ for 8~10 min and a covering agent is added to settle the slag. After standing at 700~720 ℃, the slag is removed and the ingots are cast. The ingots are then immediately water quenched. 2) Solution treatment: Place the above-mentioned ingots in a gas-protected heat treatment furnace and hold them at 400~420 ℃ for 45~48 h, then immediately cool them to room temperature with water; 3) Cyclic hot rolling and annealing: The solution-treated plate is held at 300 ℃ for 20~30 min, followed by cyclic hot rolling and annealing. The roll speed is 5~10 m / min, the temperature of the upper and lower rolls is 150~200 ℃, and the temperature difference between the upper and lower rolls is within ±6 °C. After rolling to 70~80% of the original thickness of the material, rolling is stopped and the material is immediately water-cooled to room temperature.

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