Alloy mechanical property design regulation method

Abstract

This invention relates to a method for designing and controlling the mechanical properties of magnesium alloys. Based on the mechanical property requirements of magnesium alloys, the method designs and controls their microstructure and mechanical properties, and then designs and / or selects appropriate preparation processes to rapidly control the mechanical properties of magnesium alloys. First, the quantity, size, and distribution of structures such as precipitates, twins, and dislocations in the magnesium alloy are analyzed to evaluate its mechanical properties. Then, based on the target mechanical property requirements of the magnesium alloy, one or more of the quantity, size, and distribution of these structures are controlled to improve one or more of the mechanical property indicators of the magnesium alloy. Specifically, this includes reducing the quantity of at least one of the structures such as precipitates, twins, and dislocations to improve its plasticity; or increasing the quantity of twins and dislocations and refining the average grain size to improve the strength of the magnesium alloy while maintaining good plasticity; or introducing precipitates and adjusting the dislocation arrangement to improve the alloy's plasticity while maintaining high strength.

Description

Technical Field

[0001] This invention relates to a method for designing and controlling the mechanical properties of alloys, belonging to the field of magnesium alloys. Background Technology

[0002] Magnesium alloys are currently the lightest metallic structural materials used in engineering applications, possessing advantages such as low density, high specific strength and stiffness, and good damping performance. They have broad application prospects in aerospace, automotive, and 3C (computer, communication, and consumer electronics) industries. However, with continuously increasing product performance requirements, rapidly evaluating and designing the microstructure and mechanical properties of magnesium alloys based on target performance indicators, and designing or selecting preparation processes to fabricate magnesium alloys with specific microstructures to meet performance requirements, is of great significance for solving the current challenges facing the magnesium alloy industry.

[0003] Numerous studies have been conducted on improving the mechanical properties of magnesium alloys through processes such as heat treatment and pre-deformation. Mao et al. [Mao LH, et al. Influence of Heat Treatment on Microstructures and Impact Toughness of Mg-Al-Zn Alloy[J]. JOM, 2019, 71(8): 2874-2883.] compared the impact toughness of Mg-8.10Al-0.46Zn-0.18Mn-0.18Ag (wt.%) in three different states: rolled state, solution treated (T4), and solution treated + aging treated (T6). They ultimately found that twinning is beneficial to improving the impact toughness of the alloy, while precipitation has an inhibitory effect on twinning, resulting in the T4 state alloy having the highest impact toughness. Zhang et al. [Zhang DD, et al. Improving the strength of Mg-Gd-Y-Zr-Ag alloys by multiple-pass radial forging to introduce stacking faults[J]. Materials Science and Engineering A, 2025, 933:148275] used multi-pass radial forging to adjust the mechanical properties of Mg-7.50Gd-1.53Y-0.37Zr-0.45Ag alloys. They studied the effects of four forging temperatures (25 ℃, 200 ℃, 300 ℃ and 400 ℃) on the mechanical properties of the alloys, and selected the alloy with the highest yield strength and tensile strength when forged at 300 ℃. They then compared the results with those obtained at 300 ℃. The mechanical properties of magnesium alloys forged at 300℃ using five radial forging passes (P=4, 8, 12, 16, and 32) were investigated. It was found that as the number of radial forging passes increased, the yield strength and tensile strength of the alloy increased, while the elongation decreased. The increase in alloy strength and decrease in plasticity were attributed to the high-density dislocations and stacking faults introduced during multi-pass radial forging. Using relevant formulas, the contributions of dislocations and stacking faults to the yield strength of the 300℃ / 12P sample were calculated to be 51 MPa and 31 MPa, respectively. The research approach of using different processes to modify the mechanical properties of magnesium alloys mainly involves first controlling the alloy's mechanical properties through a series of process schemes to select the optimal process parameters, and then using microstructure characterization methods to analyze the influence of microstructure on mechanical properties. This approach relies heavily on experience, resulting in a large workload, high uncertainty, and high trial-and-error costs.

[0004] This invention addresses the performance requirements of target magnesium alloys by proposing a method of "evaluating and designing the microstructure and mechanical properties of magnesium alloys based on their mechanical performance requirements, designing and / or selecting specific preparation processes, and then rapidly controlling the mechanical properties of magnesium alloys." First, the quantity, size, and distribution of precipitates, twins, and dislocations in the magnesium alloy are analyzed to evaluate their mechanical properties. Then, based on the target mechanical performance requirements of the magnesium alloy, the structures of precipitates, twins, and dislocations are designed. Appropriate heat treatment and pre-deformation processes are then designed or selected to prepare magnesium alloys with specific microstructures, achieving targeted optimization of the mechanical properties of the magnesium alloy and ultimately obtaining magnesium alloy products that meet the target performance requirements. This invention establishes a complete technical path of "performance requirements—microstructure design—process design and / or selection—preparation / optimization, iteration," providing a low-cost and rapid approach to customizing microstructures and controlling the performance of magnesium alloys, which is of significant value in guiding the actual production of magnesium alloys. No related reports have been found regarding the concept of this invention. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by proposing, for the first time, a method for designing and controlling the mechanical properties of magnesium alloys. It establishes a complete technical path of "performance requirements—microstructure design—process design and / or selection—preparation / optimization, iteration," providing insights for low-cost, rapid customization of microstructures and achieving performance control of magnesium alloys. Specific contents include:

[0006] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys. Based on the mechanical property requirements of magnesium alloys, the method designs and controls their microstructure and mechanical properties, and then designs and / or selects appropriate preparation processes to rapidly control the mechanical properties of magnesium alloys. First, the quantity, size, and distribution of precipitates, twins, and dislocations in magnesium alloy A are analyzed to evaluate its mechanical properties. Then, based on the mechanical property requirements of the target magnesium alloy B, one or more of the quantity, size, and distribution of precipitates, twins, and dislocations in magnesium alloy A are controlled to improve one or more of the mechanical property indicators of magnesium alloy A, thereby obtaining the target magnesium alloy B.

[0007] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys, specifically including: reducing the quantity of one or more of the following structures: precipitates, twins, and dislocations, thereby improving their plasticity; or, introducing precipitates to increase the quantity of twins and dislocations, refine the average grain size, and improve the strength of the magnesium alloy while maintaining good plasticity; or, introducing precipitates to adjust the dislocation arrangement, thereby improving the alloy's plasticity while maintaining high strength.

[0008] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys. The method utilizes processes such as solution treatment, pre-deformation, and aging treatment to regulate the structures of precipitates, twins, and dislocations, thereby controlling the mechanical properties of magnesium alloys. Specifically, solution treatment dissolves precipitates in the alloy, improving its plasticity; pre-deformation introduces twins and dislocations, enhancing its strength; and aging treatment alters the dislocation arrangement while simultaneously introducing precipitates, thus controlling both the strength and plasticity of the magnesium alloy.

[0009] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys. First, the quantity, size, and distribution of precipitates, twins, and dislocations in magnesium alloy A are analyzed to evaluate its mechanical properties. Then, based on the mechanical property requirements of the target magnesium alloy B, and considering the differences in mechanical properties between magnesium alloy A and the target magnesium alloy B, one or more of the quantity, size, and distribution of precipitates, twins, and dislocations in magnesium alloy A are controlled to optimize the mechanical properties of magnesium alloy A, thereby obtaining the target magnesium alloy B. Specifically, the method includes:

[0010] Based on magnesium alloy A, by reducing the number of precipitates, twins, and dislocations, its plasticity is improved, resulting in a target magnesium alloy B with good plasticity; or

[0011] Introducing precipitates increases the number of twins and dislocations, refines the average grain size, and improves the strength of magnesium alloys while maintaining good plasticity, resulting in a high-strength and highly ductile target magnesium alloy B; or

[0012] By introducing precipitates and adjusting the dislocation arrangement, the alloy's plasticity is improved while maintaining high strength, resulting in the target magnesium alloy B with both high strength and good plasticity.

[0013] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys, specifically comprising:

[0014] (1) The effect of grain refinement was evaluated by calculating the Hall-Petch relationship as shown in equation (1), and the effect of change was calculated using equation (2):

[0015]

[0016] In equation (1), The yield strength of the material. denoted as the frictional stress when a dislocation slides on the slip surface, where K is the Hall-Petch constant and d is the average grain size.

[0017]

[0018] In equation (2), The effect of average grain size variation on yield strength;

[0019] (2) The dislocation strengthening effect is evaluated using the formulas shown in equations (3) and (4), and the change effect is calculated using equation (5):

[0020]

[0021] In equation (3), For dislocation density, The table represents the average orientation difference (KAM value) between this point and other pixels, where u represents the scan step size of the EBSD test, and b is the length of the Burgers vector (Mg = 3.21 × 10⁻⁶). -10 m);

[0022]

[0023] In equation (4), To represent the effect of dislocations on improving yield strength, M is the Taylor factor, α is a constant, b is the length of the Burgers vector, and G is the shear modulus, taken as 16.7 × 10⁻⁶. 3 MPa Dislocation density;

[0024]

[0025] In equation (5), The effect of dislocation density variation on yield strength;

[0026] (3) Evaluate the precipitation enhancement effect. Precipitation enhancement is mainly achieved through the Orowan bypass mechanism. The calculation formulas are shown in equations (6) and (7). The change effect is calculated using equation (8):

[0027]

[0028] In equation (6), To demonstrate the improvement in relative yield strength, v is Poisson's ratio, r m Let r be the average radius of the circular cross-section of the precipitated particles on a random plane. m =(2 / 3) 0.5 r, where r is the average radius of the precipitated phase particles, λ p The spacing between the precipitated phase particles on the slip surface;

[0029]

[0030] In equation (7), f v The volume fraction of the precipitated phase;

[0031]

[0032] In equation (8), The effect of precipitated phase change on yield strength.

[0033] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys, comprising the following steps:

[0034] Step 1: Analyze the microstructure of magnesium alloy A, including the quantity, size, and distribution of precipitates, twins, and dislocations;

[0035] Step 2: Evaluate the mechanical properties of magnesium alloy A according to claim 5, obtain mechanical property data, and determine the contribution of microstructure to strength;

[0036] Step 3: Design the mechanical properties of the target magnesium alloy B and evaluate the differences in mechanical properties between magnesium alloy A and the target magnesium alloy B;

[0037] Step 4: Based on the mechanical property requirements of the target magnesium alloy B and its differences from those of magnesium alloy A, design at least one of the following structures for magnesium alloy: quantity, size, and distribution: precipitates, twins, and dislocations. Then, conduct a mechanical property evaluation according to claim 5, requiring that the design indicators for the mechanical properties of the target magnesium alloy B be met.

[0038] Step 5: Based on the microstructure designed in Step 4, design and / or select a preparation process to prepare a magnesium alloy with a specific microstructure, which is required to achieve the microstructure design target in Step 4. Specifically, this includes using at least one of the following processes: solution treatment, pre-deformation, and aging treatment, and controlling at least one of the following: the quantity, size, and distribution of precipitates, twins, and dislocations in the magnesium alloy.

[0039] Step Six: Perform mechanical property tests on the magnesium alloy prepared in Step Five to determine whether it meets the mechanical property design target. If the mechanical property index meets the design target, then the target magnesium alloy B is obtained.

[0040] If at least one of the mechanical properties fails to meet the design target, repeat the above steps until the target magnesium alloy B is obtained; or repeat the above steps and adjust the microstructure design and preparation process until the target magnesium alloy B is obtained.

[0041] At least one of the mechanical properties of the target magnesium alloy B is superior to that of magnesium alloy A;

[0042] If at least one of the mechanical properties of the target magnesium alloy C is better than that of magnesium alloy B, then magnesium alloy B is used to replace magnesium alloy A, and steps one through six above are repeated until the target magnesium alloy C is obtained.

[0043] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys, wherein step five specifically includes:

[0044] When a yield strength greater than 275 MPa, tensile strength greater than 360 MPa, and elongation greater than 10% are required for AQ80M magnesium alloy extruded sheets, complex twin and dislocation structures can be introduced. This is achieved through solution treatment combined with single-pass biaxial rolling. When further improvements in alloy strength are needed, such as a yield strength greater than 370 MPa, tensile strength greater than 415 MPa, and elongation greater than 5.0%, more numerous and smaller multi-scale twin and dislocation structures can be introduced. This is achieved through solution treatment combined with multi-pass biaxial rolling, resulting in a synergistic effect that significantly improves alloy strength. The solution treatment temperature is 400–420 °C, the holding time is 1–3 h, water cooling is used, and biaxial rolling is performed at room temperature with a rolling speed of 0.3–0.5 m / s. The distance between rolls per pass is reduced by 0.1%–4.0% of the sheet thickness, preferably 0.8%–1.2%.

[0045] When it is necessary to improve the strength of a solution-treated + single-pass biaxially rolled alloy while maintaining good plasticity, such that the alloy yield strength is greater than 290 MPa, tensile strength is greater than 400 MPa, and elongation is greater than 7.0%, the dislocation arrangement can be adjusted and precipitates can be introduced. Aging treatment can be used to adjust the dislocation arrangement and introduce precipitates without inducing recrystallization and dislocation annihilation, thereby improving the alloy strength while maintaining good plasticity. The aging treatment temperature is 150~200 ℃, the holding time is 20~30h, and air cooling is performed.

[0046] When it is necessary to improve the plasticity of a solution-treated and multi-pass biaxially rolled alloy while maintaining high strength, such that the alloy yield strength is greater than 320 MPa, tensile strength is greater than 385 MPa, and elongation is greater than 7.0%, the dislocation arrangement can be adjusted. Short-time aging treatment can be used to adjust the dislocation arrangement without inducing recrystallization and dislocation annihilation, thereby improving the alloy plasticity while maintaining high strength. The aging treatment temperature is 150~200 ℃, the holding time is 5~20 min, and air cooling is performed.

[0047] When AQ80M magnesium alloy extruded sheets require a yield strength greater than 260 MPa, a tensile strength greater than 390 MPa, and an elongation greater than 9.0%, the number of precipitates can be increased. Solution treatment combined with aging treatment increases the number of precipitates in the alloy while making their distribution more uniform, hindering dislocation movement and thus increasing the alloy's strength. Solution treatment alone, which dissolves the precipitates in the matrix, can improve the alloy's plasticity. The solution treatment temperature is 400~420 ℃, holding time is 1~3 h, followed by water cooling; the aging treatment temperature is 150~200 ℃, holding time is 32~40 h, followed by air cooling.

[0048] When the yield strength and tensile strength of VW93M magnesium alloy are required to be greater than 330 MPa and 420 MPa respectively, while retaining an elongation of more than 7%, precipitates are introduced and direct over-aging treatment is adopted to improve the alloy strength while maintaining good plasticity. The aging treatment temperature is 200~250 ℃, the holding time is 90~110 h, and air cooling is performed.

[0049] When an AQ80M magnesium alloy extruded sheet is required with a yield strength greater than 230 MPa, a tensile strength greater than 375 MPa, and an elongation greater than 13.0%, appropriate twin and dislocation structures can be introduced. Solution treatment followed by unidirectional rolling can be used to improve the alloy's strength while maintaining good plasticity. The solution treatment temperature is 400~420 ℃, the holding time is 1~3 h, and water cooling is performed. Unidirectional rolling is carried out at room temperature with a rolling speed of 0.3~0.5 m / s and a rolling amount of 1.0%~10.0% of the sheet thickness, preferably 7.0%~9.0%.

[0050] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys, wherein the characteristics such as the number, size, and distribution of precipitated phases are controlled by heat treatment processes such as solution treatment and aging treatment.

[0051] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys. Structures such as twins and dislocations are introduced through pre-deformation processes such as forging, rolling, extrusion, stretching, and torsion. The size, quantity, and other characteristics of structures such as twins and dislocations are controlled by methods such as controlling the amount and direction of deformation.

[0052] This invention discloses a method for designing and controlling the mechanical properties of alloys. Twins hinder dislocation movement and promote the enrichment of dislocations in the twin region. The lattice distortion caused by twins and dislocations provides a nucleation driving force for precipitates, thus refining the precipitates. By combining heat treatment and pre-deformation processes, the structure of precipitates, twins, and dislocations in magnesium alloys is synergistically controlled, thereby achieving the design and control of microstructure and properties.

[0053] Advantages and positive effects of the present invention:

[0054] This invention discloses a method for designing and controlling the mechanical properties of magnesium alloys. Based on the required mechanical properties of magnesium alloys, the method designs and controls their microstructure and mechanical properties, and then designs and / or selects specific processes to prepare magnesium alloys with specific microstructures and target properties. Through microstructure design, the method achieves the preparation of magnesium alloys with target mechanical properties, breaking through the traditional magnesium alloy R&D model of "process optimization—performance testing—microstructure characterization." It realizes a shift from "experience-based trial and error" to "design on demand," significantly improving the scientific nature of magnesium alloy strength and toughness control, and is of great significance for the development of high-performance magnesium alloys.

[0055] (1) To obtain a target magnesium alloy with designed mechanical properties, this invention involves microstructure design, designing and / or selecting specific preparation processes based on the designed microstructure, and preparing a magnesium alloy with the target mechanical properties. Through the process of target properties—designed microstructure—design and / or selected preparation processes, a magnesium alloy product that meets the mechanical property requirements is obtained. This invention reduces or mitigates the blind spots in the development of high-performance magnesium alloys, shortens the R&D cycle, and lowers development costs.

[0056] (2) This invention specifies the corresponding microstructure control path for different mechanical property targets: Strength control: Direct aging treatment is used to increase the number of precipitates and provide precipitation strengthening effect, or pre-deformation is used to introduce twin and dislocation structures, and fine grain strengthening and dislocation strengthening improve the alloy strength; Plasticity control: Solid solution treatment is used to dissolve the precipitates, reduce the resistance to dislocation movement, and improve the alloy plasticity, or aging treatment is used to introduce precipitates, so that dislocations accumulate in the precipitates, causing local stress concentration and reducing the alloy plasticity; Plasticity recovery: For magnesium alloys that have been strengthened by pre-deformation process, combined with subsequent aging treatment and other processes, the dislocation arrangement can be adjusted to improve the alloy plasticity and maintain high strength.

[0057] (3) This invention rapidly designs and / or selects a multi-process synergistic control path such as heat treatment and pre-deformation, covering various microstructure control such as precipitate dissolution / precipitation, introduction of twins, dislocation proliferation and rearrangement, and proposes a step-by-step control strategy to adjust the dislocation arrangement to restore plasticity on the basis of improving the alloy strength by introducing twins / dislocations and other structures through pre-deformation. It has outstanding practical value.

[0058] (4) This invention optimizes the mechanical properties of magnesium alloys by designing microstructures and evaluates the contribution of microstructures to the improvement of alloy strength by combining characterization methods such as OM, SEM, EBSD and TEM with corresponding calculation formulas. This provides a quantitative basis for subsequent microstructure design and control to prepare magnesium alloys with higher mechanical properties.

[0059] In summary, this invention establishes a complete technical path of "performance requirements - microstructure design - process design and / or selection - preparation / optimization and iteration", which breaks through the empirical limitations of traditional trial and error methods, evaluates the contribution of microstructure to strength improvement, greatly improves the scientific nature of the control process, significantly shortens the R&D cycle of high-performance magnesium alloys, saves costs, has practical engineering value, and is of great significance for realizing integrated control of magnesium alloy microstructure and properties. Attached Figure Description

[0060] Figure 1 This invention's core concept is compared with traditional magnesium alloy research and development approaches;

[0061] Figure 2Optical microstructure and KAM images of AQ80M magnesium alloys after solution treatment (SS) and solution treatment + single-pass biaxial rolling (R1) in Example 1 are shown, where (a, b) are SS samples and (c, d) are R1 samples.

[0062] Figure 3 Optical microstructure and KAM diagram of AQ80M magnesium alloy subjected to solution treatment and multi-pass biaxial rolling (R4) in Example 2;

[0063] Figure 4 The SEM microstructure of AQ80M magnesium alloy subjected to solution treatment + single-pass bidirectional rolling + aging treatment (R1A-P) in Example 3;

[0064] Figure 5 The images are TEM bright-field images of AQ80M magnesium alloys subjected to solution treatment + multi-pass biaxial rolling (R4) and solution treatment + multi-pass biaxial rolling + short-time aging treatment (R4A-10) in Example 4, where (a) is the R4 sample and (b) is the R4A-10 sample.

[0065] Figure 6 The SEM microstructure of the AQ80M magnesium alloy after solution treatment and aging treatment (SSA-P) in Example 5;

[0066] Figure 7 The optical microstructure of VW93M magnesium alloy in Example 6;

[0067] Figure 8 The images shown are HAADF-STEM images of the over-aged VW93M magnesium alloy in Example 6, where (a) is a low-magnification HAADF image and (b) is a high-magnification HAADF image.

[0068] Figure 9 The optical microstructure of AQ80M magnesium alloy after solution treatment and unidirectional rolling in Example 7 is shown in (a) and (b) is the SS-ND-4% sample.

[0069] Figure 10 The tensile curve of AQ80M magnesium alloy subjected to solution treatment and unidirectional rolling in Example 7 is shown. Detailed Implementation

[0070] The core idea of ​​this invention lies in: performance requirements—microstructure design—process design and / or selection—preparation / optimization and iteration, specifically verified as follows:

[0071] Example 1: Design and obtain an AQ80M magnesium alloy with a yield strength greater than 275 MPa, a tensile strength greater than 360 MPa, and an elongation greater than 10.0%.

[0072] To obtain the target magnesium alloy B with the following mechanical properties: yield strength greater than 280 MPa, tensile strength greater than 360 MPa, and elongation greater than 10.0%, the specific implementation steps are as follows:

[0073] Step 1: Optical microstructure of AQ80M magnesium alloy extruded sheet (named SS) after solution treatment as shown in the figure. Figure 2 As shown in (a), the alloy contains no twins, almost no precipitates, and has an average grain size of approximately 24.0 μm. The KAM diagram is shown below. Figure 2 As shown in (b), the dislocation density is 9.42 × 10⁻⁶. 12 m -2 ;

[0074] Step 2: Tensile mechanical properties of the SS alloy were tested. The yield strength, tensile strength and elongation were 211 MPa, 335 MPa and 15.9%, respectively. The analysis showed that the contribution of precipitation to the yield strength of the SS alloy was about 0, the contribution of average grain size to the yield strength was about 30 MPa, and the contribution of dislocation to the yield strength was about 8 MPa.

[0075] Step 3: The target magnesium alloy B requires a yield strength greater than 275 MPa, a tensile strength greater than 360 MPa, and an elongation greater than 10.0%, which is at least 64 MPa higher in yield strength and at least 25 MPa higher in tensile strength than the SS alloy.

[0076] Step 4: Introduce structures such as twins and dislocations to improve alloy strength. Twins refine the average grain size, ensuring it is no larger than 6 μm, contributing at least 30 MPa to the yield strength increase, and achieving a dislocation density of at least 3.4 × 10⁻⁶. 12 m -2 The contribution of twins and dislocations to the yield strength improvement is not less than 7 MPa, and the contribution of twins and dislocations to the yield strength is not less than 27 MPa, thereby achieving the mechanical property requirements of the target magnesium alloy B; the recommended process includes at least one of forging, rolling, extrusion, stretching, and torsion.

[0077] Step 5: In view of the product shape and process characteristics of this embodiment, in order to reduce costs and improve preparation efficiency, this embodiment selects room temperature bidirectional rolling to introduce twin and dislocation structures. The rolling speed is 0.36 m / s, and the rolling is carried out alternately in the thickness direction (ND) and the transverse direction (TD). Each direction is rolled twice. That is, when the upper surface of the sample rotates 360° and returns to the initial orientation, it is defined as one pass. The distance between the rolls is 1% of the original thickness of the plate to be rolled. After rolling one pass, the sample is named R1.

[0078] Step Six: Tensile mechanical property tests were performed on the R1 specimen. The yield strength, tensile strength, and elongation were measured to be 281 MPa, 363 MPa, and 10.7%, respectively, meeting the design requirements for the mechanical properties of the target magnesium alloy. The optical microstructure of the R1 specimen is as follows: Figure 2 As shown in (c), the average grain size is 5.2 μm, contributing 34 MPa to the increase in yield strength; the KAM diagram is as follows. Figure 2 As shown in (d), the dislocation density is 3.48 × 10⁻⁶. 13 m -2 The contribution of the structure to the yield strength improvement is 8 MPa; the synergistic effect of twins and dislocations contributes 28 MPa to the yield strength improvement, achieving the design target.

[0079] Example 2: Based on Example 1, the alloy strength was further improved, and an AQ80M magnesium alloy with a yield strength greater than 370 MPa, a tensile strength greater than 415 MPa, and an elongation greater than 5.0% was designed and obtained.

[0080] To obtain the target magnesium alloy C with a yield strength greater than 370 MPa, a tensile strength greater than 415 MPa, and an elongation greater than 5%, the specific implementation steps are as follows:

[0081] Step 1: As shown in Example 1, the R1 sample contained almost no precipitates, but a large number of twins and dislocations, with an average grain size of 5.2 μm and a dislocation density of 3.48 × 10⁻⁶. 13 m -2 ;

[0082] Step 2: The yield strength, tensile strength and elongation of the R1 sample were 281 MPa, 363 MPa and 10.7%, respectively. The analysis showed that the contribution of precipitation to the relative yield strength in the R1 alloy was about 0, the contribution of average grain size to the yield strength was about 64 MPa, the contribution of dislocations to the yield strength was about 16 MPa, and the contribution of the synergistic effect of twins and dislocations to the increase in yield strength was 28 MPa.

[0083] Step 3: The target magnesium alloy C requires a yield strength greater than 370 MPa, a tensile strength greater than 415 MPa, and an elongation greater than 5.0%. Its yield strength is at least 89 MPa higher than that of alloy R1, and its tensile strength is at least 52 MPa higher.

[0084] Step 4: Introduce more numerous and smaller multi-scale twins and dislocations to improve alloy strength. Specifically, twins refine the average grain size, ensuring it is no larger than 4 μm, contributing at least 9 MPa to the yield strength increase; the dislocation density is at least 6.5 × 10⁻⁶. 12 m -2The contribution of twins and dislocations to the improvement of yield strength is not less than 5 MPa; the contribution of twins and dislocations to the improvement of yield strength is not less than 75 MPa, thereby achieving the design requirements for the mechanical properties of the target magnesium alloy C. The results of Example 1 show that room temperature biaxial rolling can effectively improve the target properties. This example preferentially adopts room temperature biaxial rolling, but the process parameters need to be adjusted.

[0085] Step 5: Room temperature biaxial rolling is used to introduce twins and dislocations. The rolling speed is 0.36 m / s, alternating between the thickness direction (ND) and the transverse direction (TD), with two passes in each direction. One pass is defined as the sample's upper surface rotating 360° back to its initial orientation. The distance between the rolls is 1% of the original thickness of the sheet material. After each pass, the distance between the rolls decreases by 1% of the original thickness of the sheet material. That is, the distance between the rolls is 99% of the original thickness of the sheet material in the first pass, 98% in the second pass, and so on. The samples are named R according to the number of rolling passes. N (N represents the rolling pass); Due to the high requirements for yield strength and tensile strength of the target magnesium alloy, the rolling pass is set to 4 to introduce more and smaller multi-scale twins and dislocations. The sample rolled in two directions for 4 passes is named R4.

[0086] Step Six: Tensile mechanical property tests were performed on the R4 specimen. The yield strength, tensile strength, and elongation were 381 MPa, 420 MPa, and 5.1%, respectively, meeting the design requirements for the mechanical properties of the target magnesium alloy. The optical microstructure of the R4 specimen is as follows: Figure 3 As shown in (a), the average grain size is 3.5 μm, contributing 14 MPa to the increase in yield strength; the KAM diagram is as follows. Figure 3 As shown in (b), the dislocation density is 6.89 × 10⁻⁶. 13 m -2 The contribution of the structure to the yield strength improvement is 6 MPa; the synergistic effect of twins and dislocations contributes 80 MPa to the yield strength improvement, thus achieving the design target.

[0087] Combining the results of Examples 1 and 2, it can be seen that when the set target is the same as that set in Example 2, Example 1 is an exploratory process. Therefore, Examples 1 and 2 constitute a complete iterative process. To obtain a product with better performance, this process can be repeated iteratively, as specifically seen in Example 4 of this invention.

[0088] Example 3: Based on Example 1, while improving the alloy strength and maintaining good plasticity, an AQ80M magnesium alloy with a yield strength greater than 290 MPa, a tensile strength greater than 400 MPa, and an elongation greater than 7.0% was designed and obtained.

[0089] To obtain the target magnesium alloy C with a yield strength greater than 290 MPa, a tensile strength greater than 400 MPa, and an elongation greater than 7.0%, the specific implementation steps are as follows:

[0090] Step 1: As shown in Example 1, the R1 sample contained almost no precipitates, but a large number of twins and dislocations, with an average grain size of 5.2 μm and a dislocation density of 3.48 × 10⁻⁶. 13 m -2 ;

[0091] Step 2: The yield strength, tensile strength, and elongation of the R1 sample were 281 MPa, 363 MPa, and 10.7%, respectively. Analysis showed that the contribution of precipitation to the relative yield strength in the R1 alloy was approximately 0, the contribution of average grain size to the yield strength was approximately 64 MPa, the contribution of dislocations to the yield strength was approximately 16 MPa, and the contribution of the synergistic effect of twins and dislocations to the increase in yield strength was 28 MPa.

[0092] Step 3: The target magnesium alloy C requires a yield strength greater than 290 MPa, a tensile strength greater than 400 MPa, and an elongation greater than 7.0%, which is at least 9 MPa higher than the yield strength and at least 37 MPa higher than the tensile strength of the R1 alloy.

[0093] Step 4: Introducing precipitates to improve alloy strength; Research revealed that higher aging temperatures induce recrystallization and dislocation annihilation, significantly reducing alloy strength. Lower aging temperatures, however, do not induce recrystallization and dislocation annihilation, only dislocation rearrangement, resulting in a less severe decrease in alloy strength. However, this reduces the contribution of the synergistic effect of twins and dislocations to the yield strength. Therefore, the contribution of precipitates to the yield strength improvement needs to be no less than 40 MPa to meet the target mechanical property requirements of magnesium alloy C. The goal of this embodiment is to improve the strength of R1 alloy while maintaining good plasticity. The recommended process is to perform aging treatment at a relatively low temperature within the selectable temperature range.

[0094] Step 5: Introduce precipitates by aging treatment. The aging treatment temperature is set to 175 ℃, the holding time is set to 24h, and the alloy is air-cooled. The alloy after aging treatment is named R1A-P.

[0095] Step Six: Tensile mechanical property tests were performed on the R1A-P specimens. The yield strength, tensile strength, and elongation were 291 MPa, 402 MPa, and 7.6%, respectively, meeting the design requirements for the mechanical properties of the target magnesium alloy. The R1 specimen had an average grain size of 5.2 μm, contributing 34 MPa to the increase in yield strength, and a dislocation density of 3.48 × 10⁻⁶. 13 m -2The contribution of the structure to the yield strength improvement is 8 MPa, while the contribution of the synergistic effect of twins and dislocations to the yield strength improvement is reduced to 0. SEM microstructure as shown... Figure 4 As shown, the contribution of the precipitate to the relative yield strength is 42 MPa, achieving the design target.

[0096] Example 4: Based on Example 2, the alloy plasticity was improved to design and obtain an AQ80M magnesium alloy with a yield strength greater than 320 MPa, a tensile strength greater than 385 MPa, and an elongation greater than 7.0%.

[0097] To obtain the target magnesium alloy C with a yield strength greater than 320 MPa, a tensile strength greater than 385 MPa, and an elongation greater than 7.0%, the specific implementation steps are as follows:

[0098] Step 1: As shown in Example 2, the R4 sample contained almost no precipitates, but a large number of twins and dislocations, with an average grain size of 3.5 μm and a dislocation density of 6.89 × 10⁻⁶. 13 m -2 .

[0099] Step 2: The yield strength, tensile strength and elongation of the R4 sample were 381 MPa, 420 MPa and 5.1%, respectively. The analysis showed that the contribution of precipitation to the relative yield strength in the R4 alloy was about 0, the contribution of average grain size to the yield strength was about 77 MPa, the contribution of dislocations to the yield strength was about 22 MPa, and the contribution of the synergistic effect of twins and dislocations to the increase in yield strength was 80 MPa.

[0100] Step 3: The target magnesium alloy C requires a yield strength greater than 320 MPa, a tensile strength greater than 385 MPa, and an elongation greater than 7.0%.

[0101] Step 4: Improve alloy plasticity through dislocation rearrangement without inducing recrystallization and dislocation annihilation. At this point, the average grain size and dislocation density do not change significantly, and their effects on yield strength are basically the same. The contribution of the synergistic effect of twins and dislocations to yield strength is reduced. The goal of this embodiment is to improve the plasticity of R4 alloy. Based on the analysis results of Example 3, a short-time aging treatment is used to achieve dislocation rearrangement, improve alloy plasticity, and at the same time reduce the decrease in alloy strength.

[0102] Step 5: Aging treatment was used to rearrange dislocations without inducing recrystallization and dislocation annihilation. The aging treatment temperature was set to 175 ℃, the holding time was set to 10 min, and the sample was air-cooled. The sample of R4 alloy after short-time aging treatment was named R4A-10.

[0103] Step Six: Tensile mechanical property tests were performed on the R4A-10 specimen. The yield strength, tensile strength, and elongation were 331 MPa, 390 MPa, and 7.7%, respectively, meeting the design requirements for the mechanical properties of the target magnesium alloy. Figure 5 The image shows TEM bright-field images of the R4 sample before and after short-time aging treatment. It can be seen that the degree of dislocation entanglement is weakened after short-time aging treatment, and the previous irregular random arrangement gradually tends to be arranged parallel to the (0001) plane, thus improving the plasticity of the alloy.

[0104] Example 5: Design and obtain an AQ80M magnesium alloy with a yield strength greater than 260 MPa, a tensile strength greater than 390 MPa, and an elongation greater than 9.0%.

[0105] To obtain AQ80M magnesium alloy B with target mechanical properties of yield strength greater than 260 MPa, tensile strength greater than 390 MPa, and elongation greater than 9.0%, the specific implementation steps are as follows:

[0106] Step 1: As shown in Example 1, the SS alloy has no twins and almost no precipitates. Its yield strength, tensile strength, and elongation are 211 MPa, 335 MPa, and 15.9%, respectively.

[0107] Step 2: The target magnesium alloy requires a yield strength greater than 260 MPa, a tensile strength greater than 390 MPa, and an elongation greater than 9.0%, which is at least 49 MPa higher in yield strength and at least 55 MPa higher in tensile strength than the SS alloy.

[0108] Step 3: Introduce precipitates to hinder dislocation movement and improve alloy strength. The contribution to the increase in yield strength is not less than 49 MPa, thereby achieving the mechanical property requirements of the target magnesium alloy B.

[0109] Step 4: Introduce precipitates by aging treatment. The aging treatment temperature is set to 175 ℃, the holding time is set to 32 h, and the sample is air-cooled. The SS alloy sample after aging treatment is named SSA-P.

[0110] Step 5: Tensile mechanical property tests were performed on the SSA-P specimen. The yield strength, tensile strength, and elongation were 266 MPa, 391 MPa, and 9.2%, respectively, meeting the design requirements for the mechanical properties of the target magnesium alloy. The SEM microstructure of the SSA-P specimen is shown below. Figure 6 As shown, the contribution of precipitation to the relative yield strength improvement is 55 MPa, achieving the design target.

[0111] Example 6: Design and obtain a VW93M magnesium alloy with a yield strength greater than 330 MPa, a tensile strength greater than 420 MPa, and an elongation greater than 7.0%.

[0112] To obtain VW93M magnesium alloy B with target mechanical properties of yield strength greater than 330 MPa, tensile strength greater than 420 MPa, and elongation greater than 7.0%, the specific implementation steps are as follows:

[0113] Step 1: Optical microstructure of VW93M magnesium alloy (named RR) as follows Figure 7 As shown, it exhibits a typical bimodal grain distribution, including deformed grains (shown in the red dashed area) and fine equiaxed grains (shown in the black dashed area), with no obvious twins or precipitates observed;

[0114] Step 2: The yield strength, tensile strength, and elongation of the RR specimen were 250 MPa, 315 MPa, and 10.3%, respectively.

[0115] Step 3: The target magnesium alloy B requires a yield strength greater than 330 MPa, a tensile strength greater than 420 MPa, and an elongation greater than 7.0%, which is at least 80 MPa higher in yield strength and at least 105 MPa higher in tensile strength than the RR alloy.

[0116] Step 4: Introduce precipitates to improve alloy strength. The contribution of precipitates to yield strength should not be less than 80 MPa, thereby achieving the target mechanical property design index of magnesium alloy B. After exploration, over-aging treatment is recommended.

[0117] Step 5: Introduce precipitates by over-aging treatment. The aging treatment temperature is set to 225 ℃ and the aging treatment time is set to 98 h. Air cooling is performed. The alloy after over-aging treatment is named RRA-98.

[0118] Step Six: Tensile mechanical property tests were performed on the RRA-98 specimen. The yield strength, tensile strength, and elongation were 340 MPa, 423 MPa, and 8.2%, respectively, meeting the design requirements for the mechanical properties of the target magnesium alloy. The HAADF-STEM image of the RRA-98 specimen is shown below. Figure 8 As shown, the contribution of precipitation to the relative yield strength is increased to 90 MPa, achieving the design target.

[0119] The results of Example 6 show that the present invention is also applicable to VW93M magnesium alloy, and not limited to AQ80M magnesium alloy, and has good universality for magnesium alloy systems.

[0120] Example 7: Design and obtain an AQ80M magnesium alloy with a yield strength greater than 230 MPa, a tensile strength greater than 375 MPa, and an elongation greater than 13.0%.

[0121] To obtain AQ80M magnesium alloy B with target mechanical properties of yield strength greater than 230 MPa, tensile strength greater than 375 MPa, and elongation greater than 13.0%, the specific implementation steps are as follows:

[0122] Step 1: As shown in Example 1, the SS alloy has no twins and almost no precipitates. Its yield strength, tensile strength, and elongation are 211 MPa, 335 MPa, and 15.9%, respectively.

[0123] Step 2: The target magnesium alloy B requires a yield strength greater than 230 MPa, a tensile strength greater than 375 MPa, and an elongation greater than 13.0%, which is at least 19 MPa higher in yield strength and at least 40 MPa higher in tensile strength and elongation than the SS alloy.

[0124] Step 3: Introducing structures such as twins and dislocations to improve alloy strength without significantly reducing plasticity; The results of Examples 1 and 2 show that room temperature biaxial rolling can significantly improve alloy strength, but it will cause a slightly larger decrease in plasticity. The goal of this example is to improve alloy strength without significantly reducing plasticity. Therefore, room temperature uniaxial rolling is recommended.

[0125] Step 4: Introduce twin and dislocation structures by room temperature unidirectional rolling at a rolling speed of 0.36 m / s along the thickness direction (ND). Set the rolling amount to 4% of the thickness in the ND direction. Name the SS alloy sample unidirectionally rolled 4% along the ND direction as SS-ND-4%.

[0126] Step 5: Tensile mechanical properties were tested on the SS-ND-4% sample. The yield strength, tensile strength and elongation were 232 MPa, 357 MPa and 15.2% respectively. The yield strength and elongation met the requirements, but the tensile strength was insufficient. Overall, the mechanical properties of the target magnesium alloy did not meet the design requirements.

[0127] Step Six: Repeat steps one to three above, using room temperature unidirectional rolling to introduce structures such as twins and dislocations. The rolling speed is 0.36 m / s, and the rolling is carried out along the thickness direction (ND). The rolling amount is set to 8% of the thickness in the ND direction. The SS alloy unidirectionally rolled 8% sample along the ND direction is named SS-ND-8%.

[0128] Step 7: Tensile mechanical properties of the SS-ND-8% sample were tested. The yield strength, tensile strength and elongation were 234 MPa, 380 MPa and 13.4% respectively, which met the design requirements of the target magnesium alloy mechanical properties.

[0129] like Figure 9 The optical microstructure of the solution-treated + unidirectionally rolled AQ80M magnesium alloy in Example 7 shows a distinct twinned structure; as shown... Figure 10The figure shows the tensile stress-strain curve of AQ80M magnesium alloy subjected to solution treatment and unidirectional rolling in Example 7. The increase in deformation has almost no effect on the yield strength of the alloy, but it will significantly increase the tensile strength of the alloy while the elongation decreases by a very small amount, thus achieving the design target of the mechanical properties of the target magnesium alloy.

[0130] The traditional R&D approach for this technology is: process optimization—performance testing—microstructure characterization, with the typical process as follows:

[0131] Comparative Example 1: AZ80 magnesium alloy extruded disc (solution treatment + multi-directional forging)

[0132] [1] Wang Z, et al. Strengthening mechanism based on dislocation-twininteraction under room temperature multi-directional forging of AZ80 Mg alloy[J]. Journal of Materials Research and Technology, 2024, 29: 3656–3672.

[0133] Step 1: A 30 mm × 30 mm × 30 mm sample was cut axially from an AZ80 magnesium alloy extrusion disc. After being held at 415 ℃ for 1.5 h, the sample was rapidly cooled in 70 ℃ warm water to obtain the initial solution treatment sample (ST). The yield strength, tensile strength, and elongation were 150 MPa, 279 MPa, and 10.5%, respectively.

[0134] Step 2: Perform multi-directional forging (MDF) on the initial sample at room temperature at a forging rate of 3 × 10⁻⁶. -1 s -1 After each forging, the pressure is held for 10 seconds. During the multi-directional forging process, the first forging axis is perpendicular to the transverse direction (TD), the second forging axis is perpendicular to the rolling direction (RD), and the third forging axis is perpendicular to the extrusion direction (ED). Subsequent forging surfaces are rotated in the following order: TD-RD-ED-TD... After forging with a single deformation of 3% in three different directions (MDF-3%-1P), the alloy yield strength, tensile strength, and elongation are 255 MPa, 389 MPa, and 8.5%, respectively. After repeating the forging with a single deformation of 3% in three different directions four times (MDF-3%-4P), the alloy yield strength, tensile strength, and elongation are 315 MPa, 420 MPa, and 6.7%, respectively.

[0135] In Comparative Example 1, solution treatment combined with multi-directional forging was used to control the mechanical properties of the alloy. A series of schemes were developed to study the effect of deformation on the alloy's mechanical properties. It was found that as the degree of deformation increased, the alloy's strength increased but its plasticity decreased. The changes in mechanical properties were attributed to the interaction between twins and dislocations, which is a traditional research approach. Elongation

[0136] Comparative Example 2: ZT40 magnesium alloy extruded sheet (bidirectional compression)

[0137] [2] Yuan S, et al. Simultaneous enhancement of strength and plasticity in extruded ZT40 Mg alloy via double pre-compression induced multi-scale crystal defects[J]. Journal of Materials Science & Technology, 2026, 251:311–316.

[0138] Step 1: Cut a sample from the ZT40 magnesium alloy extruded sheet. Name the sample in this condition ZT40. The alloy yield strength, tensile strength and elongation are 114 MPa, 251 MPa and 24%, respectively.

[0139] Step 2: Cut a rectangular specimen with dimensions of 32 mm (extrusion direction) × 12 mm (transverse) × 7 mm (normal) from the ZT40 magnesium alloy extruded sheet. First, perform an initial compression along the transverse direction, then rotate the specimen 180° and perform a second compression with the same amount of deformation. Name the bidirectional pre-compression specimens according to the amount of deformation, such as DPC-6% (single compression deformation of 6%) and DPC-9% (single compression deformation of 9%). The yield strength, tensile strength and elongation of the DPC-6% specimen are 206 MPa, 323 MPa and 28% respectively, and the yield strength and elongation of the DPC-9% specimen are 239 MPa and 20% respectively.

[0140] Comparative Example 2 is similar to Comparative Example 1, which follows the traditional research approach. It uses bidirectional compression processes with different deformation amounts to control the mechanical properties of the alloy. The DPC-6% alloy is selected as having the best strength-plasticity match, which is attributed to the multi-scale crystal defects (dislocations, twin boundaries, and strain non-uniform regions composed of dislocations and twins) induced by bidirectional compression.

[0141]

[0142] It is understood that the above embodiments and comparative examples are merely illustrative for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for designing and controlling the mechanical properties of magnesium alloys, characterized in that: Based on the mechanical property requirements of magnesium alloys, the microstructure and mechanical properties are designed and controlled, and then corresponding preparation processes are designed and / or selected to rapidly control the mechanical properties of magnesium alloys: First, the quantity, size, and distribution of precipitates, twins, and dislocations in magnesium alloy A are analyzed to evaluate its mechanical properties; then, based on the mechanical property requirements of the target magnesium alloy B, one or more of the quantity, size, and distribution of precipitates, twins, and dislocations in magnesium alloy A are controlled to improve one or more of the mechanical property indicators of magnesium alloy A, thereby obtaining the target magnesium alloy B.

2. The method for designing and controlling the mechanical properties of magnesium alloys according to claim 1, characterized in that, Specifically, it includes: Reduce the amount of one or more of the following structures: precipitates, twins, and dislocations, to improve plasticity; Alternatively, precipitates can be introduced to increase the number of twins and dislocations, refine the average grain size, and improve the strength of magnesium alloys while maintaining good plasticity; or, precipitates can be introduced to adjust the dislocation arrangement, thereby improving the alloy's plasticity while maintaining high strength.

3. The method for designing and controlling the mechanical properties of magnesium alloys according to claim 1 or 2, characterized in that: The mechanical properties of magnesium alloys can be controlled by adjusting the structure of precipitates, twins, and dislocations through processes such as solution treatment, pre-deformation, and aging treatment. These processes include: using solution treatment to dissolve precipitates in the alloy and improve the plasticity of magnesium alloys; using pre-deformation to introduce twins and dislocations to improve the strength of magnesium alloys; and using aging treatment to change the dislocation arrangement while introducing precipitates to control the strength and plasticity of magnesium alloys.

4. A method for designing and controlling the mechanical properties of magnesium alloys according to claim 1 or 2, characterized in that: First, the quantity, size, and distribution of precipitates, twins, and dislocations in magnesium alloy A are analyzed to evaluate its mechanical properties. Then, based on the mechanical property requirements of the target magnesium alloy B, and considering the differences in mechanical properties between magnesium alloy A and the target magnesium alloy B, one or more of the quantity, size, and distribution of precipitates, twins, and dislocations in magnesium alloy A are adjusted to optimize its mechanical properties, thus obtaining the target magnesium alloy B. Specifically, this includes: Based on magnesium alloy A, by reducing the number of precipitates, twins, and dislocations, its plasticity is improved, resulting in a target magnesium alloy B with good plasticity; or Introducing precipitates increases the number of twins and dislocations, refines the average grain size, and improves the strength of magnesium alloys while maintaining good plasticity, resulting in a high-strength and highly ductile target magnesium alloy B; or By introducing precipitates and adjusting the dislocation arrangement, the alloy's plasticity is improved while maintaining high strength, resulting in the target magnesium alloy B with both high strength and good plasticity.

5. A method for designing and controlling the mechanical properties of magnesium alloys according to any one of claims 1 to 4, characterized in that: (1) The effect of grain refinement was evaluated by calculating the Hall-Petch relationship as shown in equation (1), and the effect of change was calculated using equation (2): ； In equation (1), The yield strength of the material. denoted as the frictional stress when a dislocation slides on the slip surface, where K is the Hall-Petch constant and d is the average grain size. ； In equation (2), The effect of average grain size variation on yield strength; (2) The dislocation strengthening effect is evaluated using the formulas shown in equations (3) and (4), and the change effect is calculated using equation (5): ； In equation (3), For dislocation density, The table represents the average orientation difference (KAM value) between this point and other pixels, where u represents the scan step size of the EBSD test, and b is the length of the Burgers vector (Mg = 3.21 × 10⁻⁶). -10 m); ； In equation (4), To represent the effect of dislocations on improving yield strength, M is the Taylor factor, α is a constant, b is the length of the Burgers vector, and G is the shear modulus, taken as 16.7 × 10⁻⁶. 3 MPa Dislocation density; ； In equation (5), The effect of dislocation density variation on yield strength; (3) Evaluate the precipitation enhancement effect. Precipitation enhancement is mainly achieved through the Orowan bypass mechanism. The calculation formulas are shown in equations (6) and (7). The change effect is calculated using equation (8): ； In equation (6), To demonstrate the improvement in relative yield strength, v is Poisson's ratio, r m Let r be the average radius of the circular cross-section of the precipitated particles on a random plane. m =(2 / 3) 0.5 r, where r is the average radius of the precipitated phase particles, λ p The spacing between the precipitated phase particles on the slip surface; ； In equation (7), f v The volume fraction of the precipitated phase; ； In equation (8), The effect of precipitated phase change on yield strength.

6. A method for designing and controlling the mechanical properties of magnesium alloys according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Analyze the microstructure of magnesium alloy A, including the quantity, size, and distribution of precipitates, twins, and dislocations; Step 2: Evaluate the mechanical properties of magnesium alloy A according to claim 5, obtain mechanical property data, and determine the contribution of microstructure to strength; Step 3: Design the mechanical properties of the target magnesium alloy B and evaluate the differences in mechanical properties between magnesium alloy A and the target magnesium alloy B; Step 4: Based on the mechanical property requirements of the target magnesium alloy B and its differences from those of magnesium alloy A, design at least one of the following structures for magnesium alloy: quantity, size, and distribution of precipitates, twins, and dislocations. Then, conduct a mechanical property evaluation according to claim 5, requiring that the design indicators of the mechanical properties of the target magnesium alloy B be met. Step 5: Based on the microstructure designed in Step 4, design and / or select a preparation process to prepare a magnesium alloy with a specific microstructure, which is required to achieve the microstructure design target in Step 4. Specifically, this includes using at least one of the following processes: solution treatment, pre-deformation, and aging treatment, and controlling at least one of the following: the quantity, size, and distribution of precipitates, twins, and dislocations in the magnesium alloy. Step Six: Perform mechanical property tests on the magnesium alloy prepared in Step Five to determine whether it meets the mechanical property design target. If the mechanical property index meets the design target, then the target magnesium alloy B is obtained. If at least one of the mechanical properties fails to meet the design target, repeat the above steps until the target magnesium alloy B is obtained; or repeat the above steps and adjust the microstructure design and preparation process until the target magnesium alloy B is obtained. At least one of the mechanical properties of the target magnesium alloy B is superior to that of magnesium alloy A; If at least one of the mechanical properties of the target magnesium alloy C is better than that of magnesium alloy B, then magnesium alloy B is used to replace magnesium alloy A, and steps one through six above are repeated until the target magnesium alloy C is obtained.

7. The method for designing and controlling the mechanical properties of magnesium alloys according to claim 6, characterized in that, Step five specifically includes: When a yield strength greater than 275 MPa, tensile strength greater than 360 MPa, and elongation greater than 10% are required for AQ80M magnesium alloy extruded sheets, complex twin and dislocation structures can be introduced. This is achieved through solution treatment combined with single-pass biaxial rolling. When further improvements in alloy strength are needed, such as a yield strength greater than 370 MPa, tensile strength greater than 415 MPa, and elongation greater than 5.0%, more numerous and smaller multi-scale twin and dislocation structures can be introduced. This is achieved through solution treatment combined with multi-pass biaxial rolling, resulting in a synergistic effect that significantly improves alloy strength. The solution treatment temperature is 400–420 °C, the holding time is 1–3 h, water cooling is used, and biaxial rolling is performed at room temperature with a rolling speed of 0.3–0.5 m / s. The distance between rolls per pass is reduced by 0.1%–4.0% of the sheet thickness, preferably 0.8%–1.2%. When it is necessary to improve the strength of a solution-treated + single-pass biaxially rolled alloy while maintaining good plasticity, such that the alloy yield strength is greater than 290 MPa, tensile strength is greater than 400 MPa, and elongation is greater than 7.0%, the dislocation arrangement can be adjusted and precipitates can be introduced. Aging treatment can be used to adjust the dislocation arrangement and introduce precipitates without inducing recrystallization and dislocation annihilation, thereby improving the alloy strength while maintaining good plasticity. The aging treatment temperature is 150~200 ℃, the holding time is 20~30h, and air cooling is performed. When it is necessary to improve the plasticity of a solution-treated and multi-pass biaxially rolled alloy while maintaining high strength, such that the alloy yield strength is greater than 320 MPa, tensile strength is greater than 385 MPa, and elongation is greater than 7.0%, the dislocation arrangement can be adjusted. Short-time aging treatment can be used to adjust the dislocation arrangement without inducing recrystallization and dislocation annihilation, thereby improving the alloy plasticity while maintaining high strength. The aging treatment temperature is 150~200 ℃, the holding time is 5~20 min, and air cooling is performed. When AQ80M magnesium alloy extruded sheets require a yield strength greater than 260 MPa, a tensile strength greater than 390 MPa, and an elongation greater than 9.0%, the number of precipitates can be increased. Solution treatment combined with aging treatment increases the number of precipitates in the alloy while making their distribution more uniform, hindering dislocation movement and thus increasing the alloy's strength. Solution treatment alone, which dissolves the precipitates in the matrix, can improve the alloy's plasticity. The solution treatment temperature is 400~420 ℃, holding time is 1~3 h, followed by water cooling; the aging treatment temperature is 150~200 ℃, holding time is 32~40 h, followed by air cooling. When the yield strength and tensile strength of VW93M magnesium alloy are required to be greater than 330 MPa and 420 MPa respectively, while retaining an elongation of more than 7%, precipitates are introduced and over-aging treatment is directly applied to improve the alloy strength while maintaining good plasticity. The aging treatment temperature is 200~250 ℃, the holding time is 90~110 h, and air cooling is performed. When an AQ80M magnesium alloy extruded sheet is required with a yield strength greater than 230 MPa, a tensile strength greater than 375 MPa, and an elongation greater than 13.0%, appropriate twin and dislocation structures can be introduced. Solution treatment followed by unidirectional rolling is used to improve the alloy's strength while maintaining good plasticity. The solution treatment temperature is 400~420 ℃, the holding time is 1~3 h, and water cooling is performed. Unidirectional rolling is carried out at room temperature with a rolling speed of 0.3~0.5 m / s and a rolling amount of 1.0%~10.0% of the sheet thickness, preferably 7.0%~9.0%.

8. A method for designing and controlling the mechanical properties of magnesium alloys according to claim 1 or 2, characterized in that: The characteristics of the precipitated phase, such as the quantity, size, and distribution, are controlled by heat treatment processes such as solution treatment and aging treatment.

9. A method for designing and controlling the mechanical properties of magnesium alloys according to claim 1 or 2, characterized in that: Twins and dislocations are introduced through pre-deformation processes such as forging, rolling, extrusion, stretching, and torsion. The size and quantity of twins and dislocations are controlled by adjusting the amount and direction of deformation.

10. A method for designing and controlling the mechanical properties of an alloy according to claim 1 or 2, characterized in that: Twins hinder dislocation movement and promote the enrichment of dislocations in twin regions. The lattice distortion caused by twins and dislocations provides a nucleation driving force for precipitates and refines the precipitates. By combining heat treatment and pre-deformation processes, the structures of precipitates, twins, and dislocations in magnesium alloys can be synergistically controlled, thereby achieving the design and control of microstructure and properties.

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