Short-process preparation method of high-strength and high-electromagnetic-shielding magnesium alloy plate

Abstract

The invention discloses a short-process preparation method of a high-strength and high-electromagnetic-shielding magnesium alloy plate. The short-process preparation method comprises the four steps of blank preparation and pretreatment, extrusion forming, high-temperature short-time annealing and variable-temperature asynchronous rolling. The blank is smelted by adopting high-purity magnesium and intermediate alloy, and is hot-extruded into a plate after being homogenized; and after annealing at the temperature of 480-520 DEG C, variable-temperature rolling (450 DEG C to 400 DEG C to 430 DEG C to 450 DEG C) with the asynchronous ratio of 1-1.3 is adopted, and the rolling reduction in each stage is 5-10%. According to the method, the grain size and texture are regulated and controlled through variable-temperature asymmetrical rolling, the tensile strength of the prepared plate is larger than or equal to 400 MPa, the ductility is larger than or equal to 6%, the 30-1500 MHz electromagnetic shielding effectiveness is larger than or equal to 95 dB, the conductivity is larger than or equal to 8.4% IACS, the grain size is smaller than or equal to 7.0 microns, and edge cracks and warping defects do not exist. The method is short in technological process, high in efficiency, conventional in equipment, suitable for industrial production and suitable for the fields of aerospace, automobiles and electronics.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy preparation technology, and relates to a short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy plates. Background Technology

[0002] With the rapid development of the aerospace, automotive, and electronics industries, the demand for lightweight, high-strength sheet metal with excellent electromagnetic shielding properties is becoming increasingly urgent. Magnesium alloys, due to their low density (1.74 g / cm³), are a suitable choice. 3 Magnesium alloys, with their high strength-to-weight ratio and good machinability, are ideal alternatives to traditional steel or aluminum alloys. However, existing magnesium alloy sheet manufacturing processes (such as extrusion or multi-pass rolling) suffer from defects such as poor room temperature formability, insufficient mechanical properties, coarse grains, edge cracking, and warping, which severely restrict their in-depth application in high-performance scenarios.

[0003] Traditional rolling processes, while widely used in magnesium alloy sheet preparation due to their simplicity, low cost, and high production efficiency, face challenges such as grain coarsening, strong anisotropy in texture, and deformation defects. Asynchronous rolling, as an advanced technology, introduces shear deformation by controlling the speed difference of the rolls, which can reduce rolling pressure, increase deformation, improve texture, and enhance sheet shape quality. However, the additional shear strain in asynchronous rolling easily leads to sheet warping, limiting its large-scale application. Therefore, developing a short-process method for preparing magnesium alloy sheets that balances high strength, high electromagnetic shielding performance, and eliminates edge cracks and warping has significant scientific and engineering application value.

[0004] To address the demand for high-strength, high-electromagnetic-shielding magnesium alloy sheets in the aerospace and electronics industries, existing research attempts to improve performance through alloy composition optimization, heat treatment, and deformation process improvements. For example, adding rare earth elements (such as Y and Gd) can form long-period stacked ordered (LPSO) phases, enhancing the strength and heat resistance of magnesium alloys. However, LPSO phases are prone to dissolution or coarsening during high-temperature rolling, reducing electromagnetic shielding effectiveness. While traditional isothermal asynchronous rolling can improve texture to some extent, it is difficult to simultaneously achieve high strength (tensile strength ≥400MPa), high elongation (≥6%), and excellent electromagnetic shielding performance (≥95dB in the 30-1500MHz range). Furthermore, existing processes typically require multiple rolling passes, resulting in complex processes, long production cycles, and high energy consumption, hindering industrial-scale application. Therefore, developing a short-process, high-efficiency preparation method that precisely controls microstructure and process parameters to achieve a synergistic improvement in the mechanical and electromagnetic shielding properties of magnesium alloy sheets, while avoiding edge cracks and warping defects, has become a key challenge in the field of materials science. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy sheets. By optimizing the asynchronous rolling process and combining it with a variable-temperature rolling strategy, the invention solves the problems of warping, edge cracking, and insufficient performance in the preparation of magnesium alloy sheets.

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

[0007] A short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy plates includes the following steps:

[0008] (1) Billet preparation and pretreatment: High-purity magnesium and intermediate alloy are melted and then water-cooled to obtain ingots, which are then homogenized at 450-530℃ for 9-18h to obtain homogenized magnesium alloy billets.

[0009] (2) Extrusion forming: The homogenized magnesium alloy billet obtained in step (1) is placed in an extruder and hot extruded under the conditions of extrusion temperature of 400-450℃, extrusion ratio of 5-8 and extrusion speed of 0.8-1.5m / min to process it into a sheet.

[0010] (3) High temperature short time annealing: The extruded sheet obtained in step (2) is annealed at 480-520℃ for 1-2 hours;

[0011] (4) Variable temperature asynchronous rolling: An asynchronous rolling process is adopted, with an asynchronous ratio of 1 to 1.3, and rolling is carried out in the following four stages:

[0012] First stage: Rolling at 450±10℃ for one pass with a reduction of 5 to 10%;

[0013] Second stage: Turn the plate over and roll it once at 400±10℃ with a reduction of 5 to 10%;

[0014] Third stage: Turn the plate over again and roll it once at 430±10℃ with a reduction of 5 to 10%;

[0015] Fourth stage: Turn the plate over again and roll it once at 450±10℃ with a reduction of 5 to 10%.

[0016] Preferably, in step (1), high-purity magnesium and Mg-30Y, Mg-4.1Mn master alloys, pure Zn and pure Sn are melted sequentially, refined and slag-removed, and then kept at 735-745℃ for 15-25 minutes, and then water-cooled to obtain an ingot with the composition range of Mg-(6.3~9.7wt.%)Y-(1.5~2.7wt.%)Zn-(0.8-1.3wt.%)Sn-(0.3~0.7wt.%)Mn.

[0017] Preferably, the thickness of the extruded sheet obtained in step (2) is 5 to 15 mm.

[0018] Preferably, the linear speed of the upper and lower rolls during asynchronous rolling in step (4) is 8.5 to 10.5 m / min.

[0019] Preferably, before each stage of rolling in step (4), the plate is placed in a resistance furnace at the corresponding temperature and kept warm for 8-12 minutes.

[0020] The prepared magnesium alloy sheet has a tensile strength ≥400MPa, an elongation ≥6%, an electromagnetic shielding effectiveness ≥95dB and an electrical conductivity ≥8.4% IACS in the frequency range of 30-1500MHz.

[0021] The prepared magnesium alloy sheet has a grain size ≤7.0μm, a uniform second phase distribution, and no edge cracks or warping defects.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention provides a short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy sheets. By employing a variable-temperature asynchronous rolling process (450℃→400℃→430℃→450℃) combined with a small reduction (5-10%) and specific alloy composition design, the mechanical properties, electromagnetic shielding performance, and microstructure uniformity of the magnesium alloy sheets are significantly improved. Simultaneously, edge cracks and warping defects are avoided, the process flow is shortened, and it is suitable for industrial production. The specific beneficial effects of this invention are as follows:

[0024] 1. Significantly improved mechanical properties

[0025] The variable-temperature asynchronous rolling process of this invention significantly improves the tensile strength, yield strength, and elongation of magnesium alloy sheets through high-temperature dynamic recrystallization and low-temperature grain refinement mechanisms, overcoming the bottleneck of traditional isothermal rolling where strength and plasticity are difficult to balance in high-pass deformation. The high-temperature rolling stage promotes dynamic recrystallization and releases residual stress; the low-temperature rolling stage refines grains through shear strain and dislocation strengthening; and the intermediate- and high-temperature warming stages optimize grain boundary distribution, balancing strength and plasticity. Compared to traditional isothermal processes, the sheets prepared by this invention exhibit higher tensile strength and yield strength while maintaining good plasticity, meeting the demands for high-strength and tough materials in aerospace, automotive, and other fields.

[0026] 2. Excellent electromagnetic shielding performance

[0027] This invention optimizes the texture and microstructure of the sheet metal through variable-temperature asynchronous rolling, significantly improving electromagnetic shielding effectiveness and conductivity. The prepared magnesium alloy sheet exhibits high shielding effectiveness over a wide frequency range of 30-1500MHz, especially avoiding the shielding collapse problem common in traditional processes at low frequencies. The low-temperature rolling stage enhances electromagnetic wave scattering capability through grain refinement and texture optimization, while the high-temperature warming stage controls grain boundary distribution and reduces electromagnetic wave transmission channels, thereby achieving high-efficiency shielding over a wide frequency range. This performance improvement benefits from the synergistic effect of shear strain introduced by asynchronous rolling and the variable-temperature strategy, providing reliable electromagnetic shielding performance for applications such as electronic device housings.

[0028] 3. Optimized microstructure

[0029] This invention employs a four-stage variable-temperature (high-low-medium-high-high) asynchronous rolling sequence. High-temperature passes promote dynamic recrystallization, while low-temperature passes suppress excessive grain growth, achieving grain refinement and uniform second-phase distribution. The resulting sheet material exhibits small and uniform grain size, with no segregation of the second phase, and is free from edge cracks and warping defects. The shear strain introduced by asynchronous rolling breaks the symmetrical deformation mode of traditional rolling, forming shear bands that promote grain refinement and dislocation strengthening. The variable-temperature strategy effectively controls the morphology and distribution of the long-period stacked ordered (LPSO) phase, avoiding excessive dissolution or coarsening of the LPSO phase at high temperatures and optimizing the interfacial properties between the second phase and the matrix. This optimization of the microstructure not only improves mechanical properties but also enhances electromagnetic shielding effectiveness, ensuring the stability of the sheet material's overall performance.

[0030] 4. High-efficiency, short-process technology

[0031] This invention employs a four-pass variable-temperature asynchronous rolling process, with the reduction per pass controlled at 5-10%. Through progressive strain distribution, it effectively avoids localized strain concentration, reducing the risk of cracking and mill load, and significantly shortening the traditional multi-pass rolling process. Compared to traditional processes, this invention significantly reduces the number of deformation passes, shortens the production cycle, reduces energy consumption, and greatly improves production efficiency. The small reduction and variable-temperature strategy optimize process parameter matching, ensuring performance stability and process controllability, making it suitable for large-scale production.

[0032] 5. Breaking through the limitations of traditional processes

[0033] Traditional isothermal asynchronous rolling cannot effectively suppress the dissolution or coarsening of the LPSO phase, resulting in limited mechanical and electromagnetic shielding properties, and is prone to edge cracking and warping defects. This invention, through variable-temperature asynchronous rolling, precisely controls the microstructure evolution path, overcoming the bottleneck of synergistic optimization of strength, plasticity, and electromagnetic shielding properties, significantly improving the overall performance of the sheet metal, while avoiding deformation defects in traditional processes, demonstrating significant technical advantages.

[0034] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0036] Figure 1 This is the microstructure of the magnesium alloy after rolling prepared in the comparative examples and embodiments of the present invention. Detailed Implementation

[0037] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0038] Comparative Example

[0039] The specific steps for this comparison are as follows:

[0040] Step 1: Billet Preparation and Pretreatment

[0041] High-purity magnesium, Mg-30Y, pure Zn, pure Sn, and Mg-4.1Mn master alloy were sequentially placed in a crucible according to the Mg-8Y-2Zn-1Sn-0.5Mn alloy system composition and melted using conventional methods. After refining and multiple slag removal processes, the mixture was held at approximately 740℃ for 20 minutes and then water-cooled to obtain an ingot. Subsequently, the ingot was homogenized at 450℃ for 16 hours and then air-cooled to room temperature to obtain a homogenized magnesium alloy ingot.

[0042] Step 2: Extrusion molding

[0043] The homogenized magnesium alloy billet was placed in a horizontal extrusion press and extruded into 80×12mm plates at an extrusion ratio of 7:1, an extrusion speed of 1m / min, and an extrusion temperature of 430℃.

[0044] Step 3: High-temperature short-time annealing

[0045] The extruded magnesium alloy sheet was placed in a box-type resistance furnace for short-time annealing at 500°C for 2 hours. This step aims to control grain size, eliminate residual stress, and provide a good microstructure for subsequent rolling processes.

[0046] Step 4: Variable temperature rolling to refine grains

[0047] The isothermal asynchronous rolling process is adopted, with an asynchronous ratio of 1.11. The specific steps are as follows:

[0048] First stage: Place the plate in a resistance furnace at 450℃ and hold for 8-12 minutes, then roll with a small deformation of 7%;

[0049] Second stage: Turn the plate over and place it in a resistance furnace at 450℃ for 8-12 minutes. Then roll it again at 450℃ with a small deformation of 7%.

[0050] Third stage: Turn the plate over again, place it in a resistance furnace at 450℃ and hold for 8-12 minutes, then roll it again with a small deformation of 7%.

[0051] Fourth stage: Turn the plate over again, place it in a resistance furnace at 450℃ and hold for 8-12 minutes, then roll it again with a small deformation of 7%.

[0052] Through the above process, magnesium alloy sheets with no edge cracks, no warping, uniform structure, and excellent mechanical and electromagnetic shielding properties are finally obtained.

[0053] Example:

[0054] Step 1: Billet Preparation and Pretreatment

[0055] High-purity magnesium, Mg-30Y, pure Zn, pure Sn, and Mg-4.1Mn master alloy were sequentially placed in a crucible according to the Mg-8Y-2Zn-1Sn-0.5Mn alloy system composition and melted using conventional methods. After refining and multiple slag removal processes, the mixture was held at approximately 740℃ for 20 minutes and then water-cooled to obtain an ingot. Subsequently, the ingot was homogenized at 450℃ for 16 hours and then air-cooled to room temperature to obtain a homogenized magnesium alloy ingot.

[0056] Step 2: Extrusion molding

[0057] The homogenized magnesium alloy billet was placed in a horizontal extrusion press and extruded into 80×12mm plates at an extrusion ratio of 7:1, an extrusion speed of 1m / min, and an extrusion temperature of 430℃.

[0058] Step 3: High-temperature short-time annealing

[0059] The extruded magnesium alloy sheet was placed in a box-type resistance furnace for short-time annealing at 500°C for 2 hours. This step aims to control grain size, eliminate residual stress, and provide a good microstructure for subsequent rolling processes.

[0060] Step 4: Variable Temperature Asynchronous Rolling

[0061] The variable-temperature asynchronous rolling process is adopted, with an asynchronous ratio of 1.11. The specific steps are as follows:

[0062] First stage: Place the plate in a resistance furnace at 450℃ and hold for 8-12 minutes, then roll with a small deformation of 7%;

[0063] Second stage: Turn the plate over and place it in a resistance furnace at 400℃ for 8-12 minutes. Then roll it again at 400℃ with a small deformation of 7%.

[0064] Third stage: Turn the plate over again, place it in a resistance furnace at 430℃ and hold for 8-12 minutes, then roll it again with a small deformation of 7%.

[0065] Fourth stage: Turn the plate over again, place it in a resistance furnace at 450℃ and hold for 8-12 minutes, then roll it again with a small deformation of 7%.

[0066] Through the above process, magnesium alloy sheets with no edge cracks, no warping, uniform structure, and excellent mechanical and electromagnetic shielding properties are finally obtained.

[0067] Performance testing

[0068] 1. The magnesium alloy plates prepared in the comparative examples and embodiments were subjected to room temperature mechanical property tests. The tensile stress-strain curves and performance data results are shown in Table 1.

[0069] Table 1. Room temperature mechanical properties of magnesium alloy sheets

[0070]

[0071] The comparative data in Table 1 show that the variable temperature rolling process (VT) in the embodiments significantly improves the room temperature mechanical properties of magnesium alloy sheets under the same number of rolling passes.

[0072] In the initial first pass, the performance of the two was completely identical (UTS 304±6MPa, YS228±5MPa, EL 13.5±0.5%), indicating that the effect of process differences gradually accumulates with multiple passes of deformation.

[0073] From the second pass onwards, the strengthening advantage of the VT process continues to expand: the tensile strength of VT-2P (351±4MPa) is 21MPa higher than that of the comparative IT-2P (330±8MPa), and this gain further increases in subsequent passes (VT-3P UTS 383±8MPa>IT-3P 353±5MPa; VT-4P UTS 403±7MPa>IT-4P 369±7MPa). At the same time, the yield strength is also improved, and the final rolled VT-4P (YS 332±5MPa) is 24MPa higher in absolute value than IT-4P (308±6MPa).

[0074] Although the elongation decreases during the work hardening stage (2-3 passes), the variable temperature rolling process exhibits superior plasticity control in the final rolling pass. The elongation of VT-4P (6.3±0.5%) is lower than that of IT-4P (11.4±0.8%), but significantly higher than the level of the same process in 3 passes (VT-3P 4.3±0.7%) and close to the plasticity of the IT process in 2 passes (5.4±0.6%). This indicates that it maintains effective strain coordination in the high strength range (UTS>400MPa, YS>330MPa), breaking through the bottleneck of traditional isothermal rolling where strength and plasticity are difficult to coordinate in high-pass deformation, and ultimately achieving a leapfrog improvement in comprehensive performance.

[0075] It is important to emphasize that although the final rolling elongation of the variable temperature process (6.3%) is lower than that of the isothermal process (11.4%), this value is still better than the plasticity performance of the comparative example at a similar strength level (IT-3P UTS 353MPa) (6.7%), which confirms that the variable temperature strategy can break the traditional understanding that the increase in strength of magnesium alloys is always accompanied by a sharp drop in plasticity.

[0076] 2. The electromagnetic shielding effectiveness of the magnesium alloy plates prepared in the comparative examples and embodiments was tested in the frequency range of 30-1500MHz. The electromagnetic shielding effectiveness curves and performance data results are shown in Table 2.

[0077] Table 2. Conductivity and electromagnetic shielding effectiveness of magnesium alloy plates in the frequency range of 30-1500MHz.

[0078]

[0079] Table 2 shows that the variable-temperature rolling (VT) process employed in this invention has a significant innovative effect in improving the electromagnetic properties of magnesium alloy sheets. After the first pass of rolling deformation, the electrical conductivity and electromagnetic shielding effectiveness of the rolled sheet are completely consistent. However, from the second pass onwards, the variable-temperature asynchronous rolling process exhibits a disruptive advantage. The electrical conductivity of VT-2P soars to 9.30% IACS (41% higher than IT-2P), while the electromagnetic shielding effectiveness remains at 103-118 dB across the entire frequency band, proving that the improved electrical conductivity, grain refinement, and texture optimization enhance electromagnetic wave scattering. Crucially, the electrical conductivity of VT-4P in the final rolled state (8.41% IACS) is still superior to that of IT-3P, and the lower limit of the electromagnetic shielding (SE) (99 dB) is 13 dB higher than that of IT-4P (86 dB).

[0080] This invention designs a variable-temperature asynchronous rolling sequence of "high temperature-low temperature-medium temperature-high temperature". Through precise structural control, it achieves a synergistic improvement in the mechanical and electromagnetic shielding properties of magnesium alloys, and solves the inherent contradiction of traditional isothermal process (450℃ constant temperature) in high-pass rolling. The second pass of cooling rolling at 400℃ boosted the conductivity to 9.30% IACS, a 41% improvement over the isothermal asynchronous rolling process (IT-2P, 450℃ constant temperature), while maintaining a wideband electromagnetic shielding effectiveness of 103-118dB. The final rolling pass, which restored the precise temperature matching to 450℃ (VT-4P), increased the lower limit of electromagnetic shielding effectiveness to 99dB, a 13dB improvement over the final rolling state of the isothermal asynchronous rolling process (IT-4P, SE lower limit 86dB). This effect, achieved at the cost of only sacrificing 1.4% IACS conductivity (VT-4P: 8.41% IACS vs IT-4P: 9.78% IACS), solved the problem of low-frequency shielding collapse under high cumulative deformation, while maintaining its high strength (≥400MPa, Table 1).

[0081] Figure 1 The results show the grain size distribution of the magnesium alloy sheets prepared in the comparative and example studies during the rolling process. Figure 1 It can be seen that the grain size of isothermal asynchronous rolling and variable temperature asynchronous rolling processes exhibit opposite evolution trends with each rolling pass:

[0082] In the isothermal rolling process, the grain size increases from 5.14 μm in the first pass, 5.33 μm in the second pass (+3.7% compared to the first pass), 5.77 μm in the third pass (+12.3%), to 6.01 μm in the fourth pass (+16.9%). In contrast, the VT process rapidly refines the grain size to 4.17 μm in the second pass (400℃ low-temperature rolling) (a decrease of 18.9% compared to the first pass of 5.14 μm, and a decrease of 21.8% compared to the IT-2P of the same period of 5.33 μm), and then increases to 4.93 μm (+16.1% vs VT-1P) and 6.60 μm (+28.4% vs VT-1P) in the third and fourth passes. The difference between the final rolled grain size (VT-4P 6.60 μm) and that of the isothermal asynchronous rolling process (IT-4P 6.01 μm) is only 0.59 μm.

[0083] The variable-temperature asynchronous rolling process of this invention (450℃→400℃→430℃→450℃) surpasses the traditional isothermal asynchronous rolling process in both mechanical and electromagnetic shielding performance by precisely controlling the microstructure evolution path.

[0084] The second pass at 400℃ effectively refines the grains, increases strength, and synergistically enhances dislocation strengthening and electrical conductivity. The final pass at 450℃, while inheriting the fine-grained structure produced by the previous rolling deformation, controls the grain boundary distribution through dynamic recrystallization, bridges the coarse twin phase boundaries formed in the previous stage, and eliminates the electromagnetic wave transmission channels formed by them, thus achieving a synergistic improvement in both strong plasticity and electromagnetic shielding performance.

[0085] Because traditional isothermal asynchronous rolling processes cannot suppress the dissolution of lamellar LPSO phases, the final rolling performance is strictly limited to the range of UTS<370MPa and SE low frequency<90dB. However, this variable temperature asynchronous rolling process precisely controls the microstructure evolution path through variable temperature asynchronous rolling, breaking through the limitations of strength-plasticity-functional properties of magnesium alloys in multi-pass rolling.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy plates, characterized in that, Includes the following steps: (1) Billet preparation and pretreatment: High-purity magnesium and intermediate alloy are melted and then water-cooled to obtain ingots, which are then homogenized at 450-530℃ for 9-18h to obtain homogenized magnesium alloy billets. (2) Extrusion forming: The homogenized magnesium alloy billet obtained in step (1) is placed in an extruder and hot extruded under the conditions of extrusion temperature of 400-450℃, extrusion ratio of 5-8 and extrusion speed of 0.8-1.5m / min to process it into a sheet. (3) High temperature short time annealing: The extruded sheet obtained in step (2) is annealed at 480-520℃ for 1-2 hours; (4) Variable temperature asynchronous rolling: An asynchronous rolling process is adopted, with an asynchronous ratio of 1 to 1.3, and rolling is carried out in the following four stages: First stage: Rolling at 450±10℃ for one pass with a reduction of 5 to 10%; Second stage: Turn the plate over and roll it once at 400±10℃ with a reduction of 5 to 10%; Third stage: Turn the plate over again and roll it once at 430±10℃ with a reduction of 5 to 10%; Fourth stage: Turn the plate over again and roll it once at 450±10℃ with a reduction of 5 to 10%.

2. The short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy plates according to claim 1, characterized in that, In step (1), high-purity magnesium and Mg-30Y, Mg-4.1Mn master alloys, pure Zn and pure Sn are melted sequentially, refined and slag-removed, and then held at 735-745℃ for 15-25 minutes, and then water-cooled to obtain an ingot with the composition range of Mg-(6.3~9.7wt.%)Y-(1.5~2.7wt.%)Zn-(0.8-1.3wt.%)Sn-(0.3~0.7wt.%)Mn.

3. The short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy plates according to claim 1, characterized in that, The thickness of the extruded sheet obtained in step (2) is 5-15 mm.

4. The short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy plates according to claim 1, characterized in that, In step (4), the linear speed of the upper and lower rolls during asynchronous rolling is 8.5 to 10.5 m / min.

5. The short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy plates according to claim 1, characterized in that, Before each stage of rolling in step (4), the plate is placed in a resistance furnace at the corresponding temperature and kept warm for 8-12 minutes.

6. The short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy plates according to claim 1, characterized in that, The prepared magnesium alloy sheet has a tensile strength ≥400MPa, an elongation ≥6%, an electromagnetic shielding effectiveness ≥95dB and an electrical conductivity ≥8.4%IACS in the frequency range of 30-1500MHz.

7. The short-process preparation method for high-strength, high-electromagnetic-shield magnesium alloy plates according to claim 1, characterized in that, The prepared magnesium alloy sheet has a grain size ≤7.0μm, a uniform second phase distribution, and no edge cracks or warping defects.

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