Isotropic wrought magnesium alloy plate and preparation method thereof

Abstract

The invention belongs to the technical field of magnesium alloy process optimization, and particularly relates to an isotropic wrought magnesium alloy plate and a preparation method thereof. According to the method, the magnesium alloy plate is subjected to an equal channel angular rolling-continuous bending-annealing treatment process, and the magnesium alloy plate with the double-peak separation non-basal texture is prepared; and then the magnesium alloy plate with the bimodal separation non-basal texture is subjected to pre-deformation treatment, heat treatment and subzero treatment, and the isotropic wrought magnesium alloy plate is obtained. According to the preparation method, pre-deformation treatment and subzero treatment are coupled in the preparation process, composite treatment is conducted on the bimodal magnesium alloy plate, a large number of {10-12} stretching twin crystals, high-density dislocation and high-density precipitated phases are introduced, and the in-plane anisotropy of the mechanical property of the plate is improved while the mechanical property of the plate is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium alloy process optimization, and more specifically relates to an isotropic deformable magnesium alloy plate and a preparation method thereof. Background Art

[0002] Against the backdrop of increasingly severe global energy and environmental challenges, the automotive industry is facing tremendous pressure to improve energy efficiency and reduce carbon emissions. Lightweight design, as a key technology to meet this challenge, can significantly improve vehicle endurance and reduce emissions. Among many lightweight materials, magnesium alloys have become an important choice for achieving lightweight vehicles due to their light weight and high strength. However, the typical close-packed hexagonal crystal structure of magnesium alloy sheets and the strong basal texture caused by conventional processing have a serious impact on their subsequent plastic deformation ability.

[0003] Texture control has always been a hot topic for improving the room temperature forming properties of magnesium alloy sheets. For this reason, "Effect of rolling speeds on texture modification and mechanical properties of the AZ31 sheet by acombination of equal channel angular rolling and continuous bending at high temperature[J]." (Tu J, Zhou T, Liu L, et al. J. Alloys Compd., 2018, 768: 598) and others have developed special rolling processes and found that the equal channel angular rolling-continuous bending-annealing process can prepare bimodal separation non-basal texture AZ31 magnesium alloy sheets, which will greatly improve the cupping performance of the sheet. However, the bimodal separation non-basal texture introduced by this process will cause a texture softening effect, making the sheet yield strength show strong anisotropy between the rolling direction and the transverse direction, that is, the sheet rolling yield strength is 72MPa and the transverse yield strength is 150MPa. This greatly limits the promotion and application of this type of deformed magnesium alloy sheet.

[0004] “Effect of pre-deformation on room temperature mechanical behavior and microstructure evolution of bimodal separation non-basal texture AZ31 magnesium alloy sheet[J]”(Wang JL, Hu L, Miao TH, et al. Acta. Metall. Sin., 2024, (07): 881) The study found that pre-deformation treatment can introduce a large number of {10-12} extension twins (ET), thereby significantly improving the transverse yield strength (225 MPa) of bimodal separation non-basal texture AZ31 magnesium alloy sheet. At the same time, the study "Effect of cryogenic treatment on mechanical behavior of AZ31 Mg alloy sheet with bimodal non-basal texture at room temperature[J]" (Wang LJ, Xu JY, Hu L, et al. Chinese. J. Mater. Res., 2024, 38(7): 499 DOI: 10.11901 / 1005.3093.2023.555) found that in a cryogenic environment, bimodal separation non-basal texture AZ31 magnesium alloy sheet will produce high-density dislocations and dispersed precipitates, which will cause dislocation strengthening and precipitation strengthening, and achieve a significant increase in the transverse yield strength of the sheet (105MPa). Both of the above processes can improve the mechanical properties of bimodal separation non-basal texture AZ31 magnesium alloy sheet, that is, improve the transverse yield strength of the sheet, but the in-plane anisotropy of the mechanical properties of the sheet is still not improved.

[0005] Therefore, how to achieve the in-plane isotropy of the mechanical properties of the bimodal separated non-basal textured magnesium alloy sheet while enhancing the mechanical properties has become a difficult problem that technicians in this field need to solve urgently. Summary of the invention

[0006] The object of the present invention is to provide an isotropic deformed magnesium alloy plate and a preparation method thereof. The present invention solves the problems existing in the above-mentioned prior art by coupling a rolling pre-deformation process with a liquid nitrogen deep cooling process for a magnesium alloy plate having a bimodal separation non-basal texture, thereby achieving in-plane isotropy of the mechanical properties of the magnesium alloy plate and improving the mechanical properties of the plate.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention is to provide a method for preparing an isotropic deformable magnesium alloy sheet, the steps comprising:

[0009] The magnesium alloy sheet is subjected to a process of equal-diameter angular rolling-continuous bending-annealing to prepare a magnesium alloy sheet having a bimodal separation non-basal texture;

[0010] The magnesium alloy sheet with the bimodal separation non-basal texture is subjected to pre-deformation treatment, heat treatment and deep cryogenic treatment in sequence to obtain the isotropic deformed magnesium alloy sheet.

[0011] Furthermore, the magnesium alloy sheet includes one of an AZ31 magnesium alloy sheet, an AZ61 magnesium alloy sheet and an AZ91 magnesium alloy sheet.

[0012] Furthermore, the grain C-axis of the magnesium alloy sheet with the bimodal separation non-basal texture deviates from ND to RD by 30-50°.

[0013] Furthermore, the pre-deformation treatment is room temperature rolling pre-deformation treatment, wherein the rolling pass thinning rate is 5-15%, and the roller speed is 200-800 mm / s.

[0014] The present invention introduces high-density dislocations into the grains through the pre-deformation process to achieve dislocation strengthening. On the other hand, a large number of {10-12} tensile twins are introduced into the grains to divide the grain matrix, thereby achieving a fine grain strengthening effect. At the same time, by introducing {10-12} tensile twins, the c-axis of some grain regions is deflected, weakening the texture softening effect caused by the double-peak separation non-basal texture, thereby improving the mechanical properties of the plate.

[0015] Furthermore, the heat treatment temperature is 150-300° C., and the insulation time is 10-30 minutes.

[0016] The present invention uses a heat treatment process to perform short-time recovery heating between the pre-deformation treatment and the cryogenic treatment as a connection between the previous and subsequent processes, thereby achieving a change in dislocation configuration, enhancing the effect of the liquid nitrogen cooling cryogenic treatment, and promoting the plate to produce more precipitation phases.

[0017] Furthermore, the cryogenic treatment is carried out in liquid nitrogen for 6-72 hours.

[0018] The deep cryogenic treatment in the present invention causes the lattice contraction of the pre-deformed and heat-treated plate to generate micro-strain in local areas (grain boundaries and twin interfaces), and the high-density dislocations introduced by the pre-deformation promote the precipitation of a large number of nano-scale precipitated phases at locations such as grain boundaries and twin interfaces, inhibiting the further activity of {10-12} tensile twins, thereby promoting the improvement of the mechanical properties of the magnesium alloy plate and the improvement of the in-plane anisotropy.

[0019] In the cryogenic treatment process of the present invention, the material liquid nitrogen involved is a by-product of the oxygen production industry, which is cheap, has a wide source of raw materials, is easy to store and transport, has stable chemical properties, is non-toxic and pollution-free, and has extremely low cost.

[0020] The second technical solution of the present invention is to provide an isotropic deformable magnesium alloy sheet, which is prepared by the above-mentioned preparation method.

[0021] The third technical solution of the present invention is to provide a method for improving the isotropy of a magnesium alloy sheet having a bimodal separation non-basal texture, the steps comprising:

[0022] A magnesium alloy sheet with a bimodal separation non-basal texture is subjected to a pre-deformation treatment, a heat treatment and a deep cryogenic treatment in sequence to obtain an isotropic deformed magnesium alloy sheet.

[0023] Furthermore, the magnesium alloy sheet with the bimodal separation non-basal texture is obtained by equal-diameter angle rolling-continuous bending-annealing treatment process, and the C-axis of the grain deviates from ND to RD by 30-50°.

[0024] Furthermore, the pre-deformation treatment is room temperature rolling pre-deformation treatment, wherein the rolling pass thinning rate is 5-15%, and the roller speed is 200-800 mm / s.

[0025] Furthermore, the heat treatment temperature is 150-300° C., and the insulation time is 10-30 minutes.

[0026] Furthermore, the cryogenic treatment is carried out in liquid nitrogen for 6-24 hours.

[0027] The present invention discloses the following technical effects:

[0028] The preparation process of the present invention couples pre-deformation treatment and deep cryogenic treatment to achieve composite treatment of bimodal separated non-basal textured magnesium alloy plates, wherein a large number of {10-12} tensile twins, high-density dislocations and high-density precipitated phases are introduced, thereby improving the in-plane anisotropy of the mechanical properties of the plates while enhancing the mechanical properties of the plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 This is a schematic diagram of the process flow for preparing an isotropic deformable magnesium alloy sheet in Example 1 of the present invention;

[0031] Figure 2The tensile properties of the isotropic deformed magnesium alloy sheet prepared in Example 1, wherein (a) is the true stress-strain curve, and (b) is the corresponding work hardening curve;

[0032] Figure 3 The IPF diagram (a) of the isotropic deformed magnesium alloy sheet prepared in Example 1 and the grain boundary diagram (b) of the isotropic deformed magnesium alloy sheet prepared in Example 1;

[0033] Figure 4 This is the pole figure of the isotropic deformed magnesium alloy sheet prepared in Example 1. DETAILED DESCRIPTION

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0036] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0037] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0039] The processes not specifically limited in the specific embodiments of the present invention may adopt conventional processes and parameters in the art.

[0040] Unless otherwise specified, the "room temperature" and "normal temperature" referred to in the specific embodiments of the present invention refer to 20-30°C.

[0041] The raw materials used in the specific implementation scheme of the present invention are all commercially available products.

[0042] Figure 1 This is a schematic diagram of the process flow for preparing an isotropic deformable magnesium alloy sheet according to Example 1 of the present invention.

[0043] In the specific embodiment of the present invention, commercial AZ31 magnesium alloy sheet is used for exemplary description, but it is not equivalent to a special limitation on the magnesium alloy sheet and can be replaced by other magnesium alloy sheets defined in the present application.

[0044] The process steps of equal-angle rolling-continuous bending-annealing in the specific embodiment of the present invention are:

[0045] The commercial AZ31 magnesium alloy sheet (thickness 4.3-21.2mm) was reduced to 1.26-6.21mm by hot rolling process, and then the "equal-angle rolling-continuous bending" die was installed behind the rolling mill roll and lubricated with graphite. The sheet was kept at 550℃ for 1-5min, and then immediately passed through the "equal-angle rolling-continuous bending" die to reduce the total thickness to the target sheet thickness. It was then annealed at 520℃ in a heat treatment furnace for 5h and immediately placed in water after being taken out.

[0046] Example 1

[0047] The preparation steps of isotropic deformed magnesium alloy sheet include:

[0048] S1. A commercial AZ31 magnesium alloy sheet (4.3 mm) was subjected to a process of equal-diameter angular rolling-continuous bending-annealing to prepare an AZ31 magnesium alloy sheet with a bimodal separation non-basal texture, with a thickness of 1.1 mm, and the C axis of the sheet grain deviated from ND to RD by about 40°;

[0049] S2, subjecting the AZ31 magnesium alloy sheet with bimodal separation non-basal texture to a single-pass rolling pre-deformation treatment at room temperature (pass thinning rate of 8%, roller speed of 400 mm / s) to obtain a deformed sheet;

[0050] S3, placing the deformed plate into a heat treatment furnace for heat treatment (heat treatment temperature 200° C., heat preservation time 20 min) to obtain a heat-treated plate;

[0051] S4. Place the heat-treated plate in a container filled with liquid nitrogen for cryogenic treatment (12 hours) to obtain a cryogenically treated plate, namely, an isotropic deformed magnesium alloy plate.

[0052] Example 2

[0053] The preparation steps of isotropic deformed magnesium alloy sheet include:

[0054] S1. The commercial AZ31 magnesium alloy sheet (12.5 mm) was subjected to equal-diameter angular rolling-continuous bending-annealing treatment process to prepare an AZ31 magnesium alloy sheet with a bimodal separation non-basal texture, with a thickness of 3.2 mm, and the C axis of the sheet grain deviated from ND to RD by about 37°;

[0055] S2, subjecting the AZ31 magnesium alloy sheet with bimodal separation non-basal texture to a single-pass rolling pre-deformation treatment at room temperature (pass thinning rate of 8%, roller speed of 600 mm / s) to obtain a deformed sheet;

[0056] S3, placing the deformed plate into a heat treatment furnace for heat treatment (heat treatment temperature 200° C., heat preservation time 24 min) to obtain a heat-treated plate;

[0057] S4. Place the heat-treated plate in a container filled with liquid nitrogen for cryogenic treatment (16 hours) to obtain a cryogenically treated plate, namely, an isotropic deformed magnesium alloy plate.

[0058] Example 3

[0059] The preparation steps of isotropic deformed magnesium alloy sheet include:

[0060] S1. The commercial AZ31 magnesium alloy sheet (21.2 mm) was subjected to a process of equal-diameter angular rolling-continuous bending-annealing to prepare an AZ31 magnesium alloy sheet with a bimodal separation non-basal texture, with a thickness of 5.4 mm, and the C axis of the sheet grain deviated from ND to RD by about 34°;

[0061] S2, subjecting the AZ31 magnesium alloy sheet with bimodal separation non-basal texture to room temperature single-pass rolling pre-deformation treatment (pass thinning rate of 8%, roller speed of 800 mm / s) to obtain a deformed sheet;

[0062] S3, placing the deformed plate into a heat treatment furnace for heat treatment (heat treatment temperature 200° C., heat preservation time 28 min) to obtain a heat-treated plate;

[0063] S4. Place the heat-treated plate in a container filled with liquid nitrogen for cryogenic treatment (24 hours) to obtain a cryogenically treated plate, namely, an isotropic deformed magnesium alloy plate.

[0064] Comparative Example 1

[0065] The preparation steps of magnesium alloy sheet include:

[0066] The commercial AZ31 magnesium alloy sheet (4.3 mm) was subjected to equal-diameter angular rolling-continuous bending-annealing treatment process to prepare an AZ31 magnesium alloy sheet with a bimodal separation non-basal texture. The thickness was 1.1 mm, and the C-axis of the sheet grain deviated from ND to RD by about 40°.

[0067] Comparative Example 2

[0068] The preparation steps of magnesium alloy sheet include:

[0069] S1. A commercial AZ31 magnesium alloy sheet (4.3 mm) was subjected to a process of equal-diameter angular rolling-continuous bending-annealing to prepare an AZ31 magnesium alloy sheet with a bimodal separation non-basal texture, with a thickness of 1.1 mm, and the C axis of the sheet grain deviated from ND to RD by about 40°;

[0070] S2. The AZ31 magnesium alloy sheet with a bimodal separation non-basal texture is subjected to room temperature rolling pre-deformation treatment (pass thinning rate is 8%, and the rolling roller speed is 400 mm / s) to obtain a magnesium alloy sheet.

[0071] Comparative Example 3

[0072] The preparation steps of magnesium alloy sheet include:

[0073] S1. A commercial AZ31 magnesium alloy sheet (4.3 mm) was subjected to a process of equal-diameter angular rolling-continuous bending-annealing to prepare an AZ31 magnesium alloy sheet with a bimodal separation non-basal texture, with a thickness of 1.1 mm, and the C axis of the sheet grain deviated from ND to RD by about 40°;

[0074] S2. Place the plate in a container filled with liquid nitrogen for deep cryogenic treatment (12 hours) to obtain a magnesium alloy plate.

[0075] Comparative Example 4

[0076] The preparation steps of magnesium alloy sheet include:

[0077] S1. The commercial AZ31 magnesium alloy sheet (12.5 mm) was subjected to equal-diameter angular rolling-continuous bending-annealing treatment process to prepare an AZ31 magnesium alloy sheet with a bimodal separation non-basal texture, with a thickness of 3.2 mm, and the C axis of the sheet grain deviated from ND to RD by about 37°;

[0078] S2, subjecting the AZ31 magnesium alloy sheet with bimodal separation non-basal texture to a single-pass rolling pre-deformation treatment at room temperature (pass thinning rate of 8%, roller speed of 600 mm / s) to obtain a deformed sheet;

[0079] S3. Put the deformed sheet into a heat treatment furnace for heat treatment (heat treatment temperature 200° C., holding time 24 min) to obtain a magnesium alloy sheet.

[0080] Comparative Example 5

[0081] The preparation steps of magnesium alloy sheet include:

[0082] S1. A commercial AZ31 magnesium alloy sheet (4.3 mm) was subjected to a process of equal-diameter angular rolling-continuous bending-annealing to prepare an AZ31 magnesium alloy sheet with a bimodal separation non-basal texture, with a thickness of 1.1 mm, and the C axis of the sheet grain deviated from ND to RD by about 40°;

[0083] S2, subjecting the AZ31 magnesium alloy sheet with bimodal separation non-basal texture to a single-pass rolling pre-deformation treatment at room temperature (pass thinning rate of 8%, roller speed of 400 mm / s) to obtain a deformed sheet;

[0084] S3. Place the deformed sheet in a container filled with liquid nitrogen for cryogenic treatment (12 hours) to obtain a cryogenically treated sheet.

[0085] Comparative Example 6

[0086] The preparation steps of magnesium alloy sheet include:

[0087] S1. A commercial AZ31 magnesium alloy sheet (4.3 mm) was subjected to a process of equal-diameter angular rolling-continuous bending-annealing to prepare an AZ31 magnesium alloy sheet with a bimodal separation non-basal texture, with a thickness of 1.1 mm, and the C axis of the sheet grain deviated from ND to RD by about 40°;

[0088] S2, placing the AZ31 magnesium alloy plate with bimodal separation non-basal texture into a heat treatment furnace for heat treatment (heat treatment temperature 200° C., holding time 20 min) to obtain a heat-treated plate;

[0089] S3. Place the heat-treated plate in a container filled with liquid nitrogen for cryogenic treatment (12 hours) to obtain a cryogenically treated plate.

[0090] The comprehensive mechanical properties of the magnesium alloy plates prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were tested, and the results are shown in Table 1.

[0091] The test method is:

[0092] The prepared plates were electrospark machined to obtain “dog bone” tensile specimens along the rolling direction (RD) and transverse direction (TD), and then the specimens were tested on a SANS testing machine at a speed of 0.001s. -1 The room temperature uniaxial tensile test was carried out at a constant strain rate of . To ensure the accuracy of the mechanical properties test, the above experiments were repeated 3 times.

[0093] Table 1

[0094]

[0095] It can be seen from the data in Table 1 that in the embodiment of the present invention, the pre-deformation treatment and the cryogenic treatment are coupled, and the heat treatment is used as the connection process between the pre-deformation treatment and the cryogenic treatment. By simultaneously introducing a large number of {10-12} tensile twins, high-density dislocations and high-density precipitation phases into the plate, the in-plane anisotropy of the mechanical properties of the plate is improved while improving the mechanical properties of the plate. In Comparative Example 1, the AZ31 magnesium alloy plate with a bimodal separation non-basal texture that has not undergone pre-deformation treatment, heat treatment, and cryogenic treatment has a significant texture softening effect, resulting in a yield strength of only 70.32MPa in the rolling direction of the plate, and the in-plane anisotropy of the mechanical properties is significant, that is, the ratio of the yield strength to the tensile strength in the transverse direction and the rolling direction of the plate differs by 0.26. In comparative example 2, the magnesium alloy sheet that has not been subjected to heat treatment and cryogenic treatment lacks the pinning of the dispersed precipitated nanophases on the dislocations and the hindering effect on the {10-2} tensile twin interface. Although the mechanical properties of the sheet are significantly improved by dislocation strengthening, the in-plane anisotropy of the mechanical properties is significant, that is, the ratio of the yield strength to the tensile strength in the transverse direction and the rolling direction of the sheet differs by 0.31. In comparative example 3, the magnesium alloy sheet that has not been subjected to pre-deformation treatment and heat treatment has no introduction of high-density dislocations and reconstruction of dislocation configurations. The size and volume fraction of the dispersed nanophase introduced into the sheet through cryogenic treatment are relatively small. Although the mechanical properties of the sheet are improved, the in-plane anisotropy of the mechanical properties is significant, that is, the ratio of the yield strength to the tensile strength in the transverse direction and the rolling direction of the sheet differs by 0.18. In Comparative Example 4, there is no plate subjected to cryogenic treatment, and its plate performance index is close to that of Comparative Example 2, and the in-plane anisotropy of the plate mechanical properties is significant, that is, the plate transverse and rolling directions have a difference of 0.36 in the ratio of yield strength to tensile strength. In Comparative Example 5, there is no plate subjected to heat treatment, and its mechanical properties are significantly improved. However, due to the lack of reconstruction of dislocation configuration by heat treatment, the precipitation behavior and distribution law of nano-precipitated phases in the subsequent cryogenic treatment process will be affected, and thus the in-plane anisotropy of the plate mechanical properties is still relatively significant, that is, the plate transverse and rolling directions have a difference of 0.19 in the ratio of yield strength to tensile strength. In Comparative Example 6, there is no plate subjected to pre-deformation treatment, and its plate performance index is close to that of Comparative Example 3, and the in-plane anisotropy of the plate mechanical properties is significant, that is, the plate transverse and rolling directions have a difference of 0.22 in the ratio of yield strength to tensile strength.

[0096] Figure 2: The tensile properties of the isotropic deformed magnesium alloy sheet prepared in Example 1, wherein (a) is the true stress-strain curve, and (b) is the corresponding work hardening curve; it can be seen from the figure that the yield strength YS (173.07 MPa) of the RD sample of the sheet prepared in the present invention is only slightly lower than that of the TD sample (185.17 MPa), while the YS of the bimodal separated non-basal texture AZ31 magnesium alloy sheet prepared by equal-diameter angular rolling-continuous bending-annealing treatment process along RD and TD stretching are 72 MPa and 150 MPa, respectively. By comparison, it can be seen that this preparation method not only improves the mechanical properties of the plate, but also significantly improves the in-plane anisotropy of the mechanical properties of the plate, thereby achieving the in-plane isotropy of the mechanical properties of the plate.

[0097] Figure 3 The IPF diagram (a) of the isotropic deformed magnesium alloy sheet prepared in Example 1 and the grain boundary diagram (b) of the isotropic deformed magnesium alloy sheet prepared in Example 1; Figure 4 is the pole figure of the isotropic deformed magnesium alloy sheet prepared in Example 1. Figure 3-4 It can be seen that the preparation method of the present invention introduces a large number of parallel or crossed lamellar {10-12} tensile twins into the plate, which divide the grain matrix and thus achieve a fine grain strengthening effect. At the same time, the introduction of {10-12} tensile twins causes the c-axis of some grain regions to deflect, weakening the texture softening effect caused by the double peak separation non-basal texture.

[0098] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0099] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an isotropic deformable magnesium alloy sheet, characterized in that the steps include: The magnesium alloy sheet is subjected to a process of equal-diameter angular rolling-continuous bending-annealing to prepare a magnesium alloy sheet having a bimodal separation non-basal texture; The magnesium alloy sheet with the bimodal separation non-basal texture is subjected to pre-deformation treatment, heat treatment and deep cryogenic treatment in sequence to obtain the isotropic deformed magnesium alloy sheet.

2. The preparation method according to claim 1, characterized in that The magnesium alloy sheet comprises one of AZ31 magnesium alloy sheet, AZ61 magnesium alloy sheet and AZ91 magnesium alloy sheet; and / or, the grain C-axis of the magnesium alloy sheet with bimodal separation non-basal texture deviates from ND to RD by 30-50°.

3. The preparation method according to claim 1, characterized in that: The pre-deformation treatment is room temperature rolling pre-deformation treatment.

4. The preparation method according to claim 3, characterized in that: The rolling pass reduction rate in the room temperature rolling pre-deformation treatment is 5-15%, and the rolling roller speed is 200-800 mm / s.

5. The preparation method according to claim 1, characterized in that: The heat treatment temperature is 150-300° C., and the heat preservation time is 10-30 minutes.

6. The preparation method according to claim 1, characterized in that: The cryogenic treatment is carried out in liquid nitrogen for 6-72 hours.

7. An isotropic deformable magnesium alloy sheet, characterized in that: The isotropic deformable magnesium alloy sheet is prepared by any preparation method according to claims 1-6.

8. A method for improving the isotropy of a magnesium alloy sheet having a bimodal separation non-basal texture, characterized in that the steps include: The magnesium alloy sheet with bimodal separation non-basal texture is subjected to pre-deformation treatment, heat treatment and deep cryogenic treatment to obtain an isotropic deformed magnesium alloy sheet.

9. The method according to claim 8, characterized in that The magnesium alloy sheet with bimodal separation non-basal texture is obtained by equal-angle rolling-continuous bending-annealing treatment process, and the C axis of the grain deviates from ND to RD by 30-50 degrees.

10. The method according to claim 8, characterized in that The pre-deformation treatment is room temperature rolling pre-deformation treatment, wherein the rolling pass thinning rate is 5-15%, and the roller speed is 200-800 mm / s; and / or, The heat treatment temperature is 150-300°C and the holding time is 10-30min; and / or, The cryogenic treatment is performed by placing the plate in liquid nitrogen for 6-72 hours.

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