A high-toughness dual-phase heterogeneous ultrafine-grain magnesium-lithium alloy, a preparation method and application thereof

Abstract

The application belongs to the technical field of high-performance ultra-light metal material processing and manufacturing, and particularly relates to a high-strength and high-toughness dual-phase heterogeneous ultra-fine-grain magnesium-lithium alloy as well as a preparation method and application thereof. The high-strength and high-toughness dual-phase heterogeneous ultra-fine-grain magnesium-lithium alloy comprises an ultra-fine-grain alpha-Mg phase matrix and micron-sized beta-Li phase particles embedded in the alpha-Mg phase matrix, and the micron-sized beta-Li phase particles account for 10%-30% of the total volume of the magnesium-lithium alloy. In the application, a magnesium matrix with ultra-fine / nano-crystalline and a beta-Li phase with excellent plasticity are heterogeneously compounded through a powder metallurgy process, and the synergistic effect of the two is utilized to realize the synchronous improvement of the strength and plasticity of the alloy.

Description

Technical Field

[0001] This invention belongs to the field of high-performance ultralight metal material processing and manufacturing technology, specifically relating to a high-strength and tough dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy, its preparation method and application. Background Technology

[0002] Magnesium alloys, as one of the lightest metallic structural materials, possess high specific strength, excellent electromagnetic shielding, and damping properties, making them promising candidates for lightweight applications. However, their poor plastic deformation capacity, limited by the insufficient room-temperature slip system resulting from their hexagonal close-packed (HCP) crystal structure, severely restricts their large-scale application.

[0003] Although the Hall-Petch effect can significantly improve the strength of magnesium alloys through grain refinement, the resulting ultrafine / nanocrystalline structure is prone to dislocation annihilation at grain boundaries, leading to poor work hardening ability and local instability during plastic deformation, resulting in extremely low elongation. While heterogeneous structure design improves plasticity by introducing micron-sized phases, it is limited by the intrinsic characteristic of magnesium alloys' hexagonal close-packed (HCP) structure having few slip systems. To achieve the desired plasticity, a large volume fraction of soft phase must be introduced, ultimately resulting in a significant reduction in the overall strength of the material. This still cannot solve the fundamental contradiction that strength and plasticity cannot be improved in a coordinated manner. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength and tough dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy, its preparation method and application, thereby overcoming the shortcomings of the prior art. Through powder metallurgy, an ultrafine / nanocrystalline magnesium matrix is ​​heterogeneously composited with a β-Li phase with excellent plasticity. By utilizing the synergistic effect of the two, the strength and plasticity of the alloy are simultaneously improved.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a high-strength and tough dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy, comprising an ultrafine-grained α-Mg phase matrix and micron-sized β-Li phase particles embedded therein, wherein the micron-sized β-Li phase particles account for 10%-30% of the total volume of the magnesium-lithium alloy.

[0006] Secondly, the present invention provides a method for preparing a high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy, comprising the following steps: Magnesium-based powder (containing no Li element) was ball-milled to obtain nanocrystalline magnesium-based powder A; Magnesium-lithium alloy was crushed to obtain β-Li phase magnesium-lithium alloy powder B. Nanocrystalline magnesium-based powder A was mixed with β-Li phase magnesium-lithium alloy powder B to obtain mixed powder C; High-strength and tough dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy is obtained by vacuum hot pressing and plastic deformation processing of mixed powder C.

[0007] The powder metallurgy process route (mechanical alloying, mixing, consolidation, deformation) of this invention has a clear flow and controllable parameters, making it easy to achieve industrial production. The prepared alloy rods, plates, etc. can be used for lightweight, high-performance, complex structural parts.

[0008] Thirdly, this invention provides applications of high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloys in aerospace and transportation. This alloy is particularly suitable for applications requiring lightweight, high-strength, and highly ductile structural materials.

[0009] The beneficial effects of this invention are: (1) This invention utilizes the ultrafine / nanocrystalline α-Mg phase to provide high strength, while introducing the BCC-structured β-Li phase to provide excellent plastic deformation capability. Using the Li-free α-Mg phase as the initial material solves the problem of the difficulty in refining / nano-sizing Li-containing magnesium-based powders. The β-Li phase, as a soft phase, coordinates strain during deformation, suppressing early instability and fracture of the ultrafine-grained magnesium alloy. Simultaneously, the presence of the two-phase interface generates heterogeneous deformation-induced (HDI) stress, achieving a synergistic improvement in strength and plasticity. Furthermore, both the β-Li phase and the α-Mg matrix are magnesium-based alloys, possessing good chemical compatibility and interfacial bonding strength, avoiding the problem of easy interface cracking during traditional heterogeneous material composites, and ensuring effective load transfer.

[0010] (2) The preparation method of the present invention is simple to operate and easy to realize industrial production. By controlling the ratio, particle size and distribution of nanocrystalline magnesium matrix powder and microcrystalline β-Li phase powder, the microstructure of the alloy can be flexibly designed, thereby realizing customized preparation of different performance levels (such as high strength type, high plasticity type, and high strength and toughness balance type).

[0011] (3) The high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy prepared by the present invention has a compressive strength of 472-660 MPa and a fracture strain of 5.4-24.3%, which can be applied to lightweight, high-performance complex structural parts. Attached Figure Description

[0012] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0013] Figure 1 A scanning electron microscope (SEM) backscattered electron image of the high-strength and tough dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy prepared in Example 1 of the present invention; Figure 2 This is a comparison of the room temperature compressive strength-fracture strain curves of the materials prepared in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0014] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components whose manufacturers are not specified are all commercially available conventional products.

[0015] This invention addresses the technical problems of poor plasticity, weak work hardening ability, and strength reduction in heterogeneous magnesium alloys due to the introduction of ductile phases. It proposes a two-phase heterogeneous structure design, comprising an ultrafine / nanocrystalline α-Mg matrix phase and an embedded micron-sized β-Li ductile phase. The β-Li phase has a body-centered cubic structure, exhibiting good plasticity and strong bonding with the magnesium matrix. The high plasticity of the β-Li phase significantly improves the deformation capacity of the ultrafine-grained magnesium alloy while maintaining high strength, achieving a synergistic improvement in both strength and plasticity. This alloy exhibits low density and excellent overall mechanical properties.

[0016] In one aspect, a high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy is provided, comprising an ultrafine-grained α-Mg phase matrix and micron-sized β-Li phase particles embedded therein, wherein the micron-sized β-Li phase particles account for 10%-30% of the total volume of the magnesium-lithium alloy.

[0017] The ultrafine-grained α-Mg matrix (containing no Li) provides extremely high strength, while the uniformly distributed micron-sized β-Li phase (accounting for 10%-30%) alleviates stress concentration and suppresses local instability with its rich slip system of BCC structure. It also generates a significant back stress strengthening effect through the coordinated deformation of the two-phase interface, thus maintaining the ultra-lightweight properties of magnesium-lithium alloy while taking into account high strength and high plasticity.

[0018] In some other embodiments, the average particle size of the ultrafine α-Mg phase is 20-200 nm; The average particle size of the micron-sized β-Li phase particles is 5-1000 μm.

[0019] In some other embodiments, the high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy has a compressive strength of 472-660 MPa and a fracture strain of 5.4-24.3%.

[0020] Secondly, a method for preparing high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy is provided, including the following steps: Magnesium-based powder (containing no Li element) was ball-milled to obtain nanocrystalline magnesium-based powder A; Magnesium-lithium alloy was crushed to obtain β-Li phase magnesium-lithium alloy powder B. Nanocrystalline magnesium-based powder A was mixed with β-Li phase magnesium-lithium alloy powder B to obtain mixed powder C; High-strength and tough dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy is obtained by vacuum hot pressing and plastic deformation of mixed powder C.

[0021] Nanocrystalline magnesium-based powder and β-Li phase powder were prepared by ball milling and crushing processes, respectively. The nanocrystalline magnesium alloy powder does not contain Li, which ensures the nanocrystalline characteristics of the α-Mg matrix and the purity of the β-Li phase from the source. Through quantitative mixing and vacuum hot pressing, the uniform dispersion of micron-sized β-Li phase particles in the matrix (volume fraction 10%-30%) was achieved, effectively overcoming the defects of traditional casting methods such as easy component segregation and difficulty in controlling phase size. Finally, combined with plastic deformation processing, the grains were further refined and the interfacial bonding between the two phases was strengthened, thereby achieving the best match between strength and plasticity while ensuring the density of the material.

[0022] In some other embodiments, the magnesium-based powder is pure magnesium powder or magnesium alloy powder, and the purity of the magnesium-based powder is ≥99.9%; In the ball milling process, the mass ratio of ball to material is (10-30):1, the milling time is 10-100 h, the milling speed is 200-500 r / min, and the milling atmosphere is an inert gas atmosphere. A process control agent is also added during the milling process at a dosage of 0.5-1.5 wt.%; the process control agent includes stearic acid and sodium stearate. The process control agent is used to prevent cold welding of magnesium-based powder.

[0023] For example, the magnesium alloy powder is AZ91 magnesium alloy powder, the mass ratio of the ball milling material is any one or a range of 10:1, 20:1 and 30:1, the ball milling time is any one or a range of 10, 20, 40, 60, 80 and 100 h, and the ball milling speed is any one or a range of 200, 300, 400 and 500 r / min.

[0024] Preferably, the ball-to-material ratio is 20:1, the rotation speed is 300 r / min, and the ball milling is carried out for 40 h under argon protection.

[0025] In some other embodiments, the mass fraction of lithium in the magnesium-lithium alloy is 10.3%-15%; preferably, the mass fraction of lithium in the magnesium-lithium alloy is 11.5%-15% to ensure a single β-Li phase is obtained.

[0026] For example, the magnesium-lithium alloy is an LA141 ingot. As the lightest metallic structural material, magnesium-lithium (Mg-Li) alloys precipitate a body-centered cubic (BCC) β-Li phase when the lithium content exceeds approximately 10.3%. This phase has a higher slip system compared to the traditional hexagonal close-packed (HCP) structure, giving the alloy excellent room-temperature plastic deformation capability. At the same time, the good interfacial bonding characteristics between the β-Li phase and the α-Mg matrix, through the formation of a two-phase heterogeneous structure, achieve a balance between strength and plasticity.

[0027] The crushing process is either mechanical crushing or pneumatic crushing, and the crushing atmosphere is an inert gas atmosphere.

[0028] In some other embodiments, the volume ratio of nanocrystalline magnesium-based powder A to β-Li phase magnesium-lithium alloy powder B is (70-90):(10-30); the mixing time is 1-3 hours. The average particle size of nanocrystalline magnesium-based powder A is <100 nm; The average particle size of β-Li phase magnesium-lithium alloy powder B is 5-1000 μm.

[0029] For example, the volume ratio of nanocrystalline magnesium-based powder A to β-Li phase magnesium-lithium alloy powder B is 70:30, 80:20, and 90:10.

[0030] In other embodiments, the vacuum hot pressing temperature is 100-500℃, the pressure is 200-600MPa, the holding time is 1-4 h, and the vacuum degree is ≤1×10 -2 Pa.

[0031] For example, the temperature of vacuum hot pressing is any value or range of 100, 150, 300, 450 and 500°C, the pressure is any value or range of 200, 300, 400, 500 and 600 MPa, and the heat and pressure holding time is any value or range of 1, 2, 3 and 4 h.

[0032] In some other embodiments, the temperature of plastic deformation processing is 200-450°C, the extrusion ratio is (10-40):1, the deformation amount per pass is 10%-50%, and the extrusion speed is 0.5-5 mm / s.

[0033] For example, the temperature of plastic deformation processing is any one or a range of 200, 300, 400 and 450°C, the extrusion ratio is any one or a range of 10:1, 20:1, 30:1 and 40:1, and the single-pass deformation amount is any one or a range of 10%, 20%, 30%, 40% and 50%.

[0034] Thirdly, it provides applications of high-strength and tough dual-phase heterogeneous ultrafine-grained magnesium-lithium alloys in aerospace and transportation.

[0035] The following is a further explanation with reference to specific embodiments and comparative examples: Example 1 A high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy and its preparation method, specifically including the following steps: Step 1: Prepare nanocrystalline magnesium-based powder A.

[0036] AZ91 magnesium alloy powder with a purity greater than 99.9% was placed in a planetary high-energy ball mill at a ball-to-powder ratio of 20:1 and a rotation speed of 300 r / min. The milling was carried out for 40 h under argon protection, with 1 wt% stearic acid (1 wt% of the AZ91 magnesium alloy powder) added as a process control agent. After milling, the grain size of the powder was approximately 60 nm.

[0037] Step 2: Prepare β-Li phase magnesium-lithium alloy powder B.

[0038] The LA141 ingot was mechanically crushed under argon protection and then sieved to obtain β-Li phase powder with an average particle size of 600 μm.

[0039] Step 3: Prepare mixed powder C.

[0040] 70% by volume of nanocrystalline magnesium-based powder A and 30% by volume of β-Li phase magnesium-lithium alloy powder B were placed in a V-type mixer and mixed for 2 hours to obtain mixed powder C.

[0041] Step 4: Vacuum hot pressing consolidation.

[0042] The mixed powder C was loaded into a graphite mold and sintered in a vacuum hot press furnace. The sintering temperature was 150℃, the pressure was 300MPa, and the temperature and pressure were held for 2 hours to obtain an ingot with a density greater than 99%.

[0043] Step 5: Hot extrusion molding.

[0044] The ingot obtained in step 4 was preheated at 300℃ for 30 minutes, and then hot-extruded on an extrusion press at an extrusion ratio of 10:1 and an extrusion speed of 1 mm / s to obtain a bar with a diameter of 16 mm. This bar is a high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy.

[0045] Depend on Figure 1 The scanning electron microscope (SEM) backscattered electron image of the high-strength and tough dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy prepared in Example 1 shows that dark gray micron-sized β-Li phase particles are uniformly distributed in the gray ultrafine-grained α-Mg matrix. The β-Li phase particles do not disappear due to the diffusion of Li elements into the α-Mg matrix.

[0046] Example 2 The difference from Example 1 is that in step 3, the volume fraction of β-Li phase magnesium-lithium alloy powder B is adjusted to 20%; the remaining steps remain unchanged.

[0047] Example 3 The difference from Example 1 is that in step 3, the volume fraction of β-Li phase magnesium-lithium alloy powder B is adjusted to 10%; the other steps remain unchanged.

[0048] Example 4 The difference from Example 3 is that in step 1, pure magnesium powder is used instead of AZ91 alloy powder for mechanical alloying to obtain a submicron crystalline magnesium matrix with higher plasticity; the remaining steps remain unchanged.

[0049] Comparative Example 1 The difference from Example 1 is that only the nanocrystalline magnesium alloy powder A obtained in step 1 is used for direct solidification and forming, without adding β-Li phase magnesium-lithium alloy powder B, to obtain pure nanocrystalline magnesium rods.

[0050] Comparative Example 2 The difference from Example 4 is that only the nanocrystalline pure powder A obtained in step 1 is used for direct solidification and forming, without adding β-Li phase magnesium-lithium alloy powder B, to obtain pure submicron crystalline magnesium rods.

[0051] Comparative Example 3 The difference from Example 1 is that in step 1, the addition of 1 wt% stearic acid is omitted; the remaining steps remain unchanged.

[0052] Comparative Example 4 The difference from Example 1 is that AZ91 magnesium alloy powder with a purity greater than 99.9% and LA141 ingot are ball-milled together to obtain a mixed powder; the remaining steps remain unchanged.

[0053] Comparative Example 5 The difference from Example 1 is that in step 3, the volume fraction of β-Li phase magnesium-lithium alloy powder B is adjusted to 5%; the other steps remain unchanged.

[0054] Comparative Example 6 The difference from Example 1 is that in step 3, the volume fraction of β-Li phase magnesium-lithium alloy powder B is adjusted to 50%; the remaining steps remain unchanged.

[0055] Comparative Example 7 The difference from Example 1 is that in step 1, LA43M magnesium-lithium alloy with a Li content of 4 wt.% is used; the remaining steps remain unchanged.

[0056] Comparative Example 8 The difference from Example 1 is that steps 1-3 are omitted, and the AZ91 powder is directly subjected to vacuum hot pressing and extrusion molding.

[0057] Comparative Example 9 The difference from Example 1 is that steps 1-4 are omitted, and the LA141 ingot is directly extruded.

[0058] Performance testing The compressive strength and fracture strain of the samples prepared in the examples and comparative examples were tested, and the test results are shown in Table 1. The yield strength, compressive strength, and fracture strain tests were performed according to GB / T 7314-2017, and the hardness test was performed according to GB / T 21838.1-2019.

[0059] Table 1 Performance Test Results

[0060] Table 1 shows that the alloy prepared in Example 1 has a compressive strength of 569 MPa and a fracture strain of 7.8%. Compared with Comparative Example 1 (pure nanocrystalline magnesium, compressive strength 481 MPa, elongation 4.6%), ... Figure 2 As shown, the strength and plasticity of Example 1 are increased by 18% and 70% respectively, achieving an excellent balance between strength and plasticity.

[0061] The alloy prepared in Example 2 exhibited a compressive strength of 647 MPa and a fracture strain of 6.0%, demonstrating higher strength. The alloy prepared in Example 3 exhibited a compressive strength of 652 MPa and a fracture strain of 5.4%, also demonstrating higher strength.

[0062] The alloy prepared in Example 4 has a compressive strength of 472 MPa and an increased compressive fracture strain of 24.3%. Compared with Comparative Example 2 (pure submicron crystalline magnesium, compressive strength 324 MPa, elongation 17.8%), the strength and plasticity of Example 4 are increased by 46% and 37%, respectively, achieving an excellent balance between strength and plasticity.

[0063] In Comparative Example 3, due to the absence of stearic acid, the AZ91 magnesium-based material could not achieve sufficient grain refinement through mechanical ball milling and welding-crushing. The magnesium grain size after ball milling was approximately 300 nm.

[0064] In Comparative Example 4, because AZ91 powder was mixed with LA141 in the early stage of ball milling, Li elements in LA141 diffused into AZ91 powder during the ball milling process, making it difficult to refine / nanosize AZ91 powder.

[0065] In Comparative Example 5, due to insufficient addition of β-Li phase magnesium-lithium alloy powder, significant high-density deformation induced (HDI) stress could not be generated, thus failing to achieve the effect of strengthening and plasticizing.

[0066] In Comparative Example 6, due to insufficient addition of β-Li phase magnesium-lithium alloy powder, significant high-intensity deformation induced (HDI) stress could not be generated, thus failing to achieve the desired reinforcing effect.

[0067] Comparative Example 7 uses LA43M magnesium-lithium alloy containing Li. During the mechanical alloying process, the material is difficult to nanoscale and cannot play a significant strengthening role.

[0068] The material of Comparative Example 8, which was formed by vacuum hot pressing and extrusion, has weak impact resistance. Under long-term load, defects continue to expand, and early failure is likely to occur.

[0069] The as-cast LA141 alloy in Comparative Example 9 has inherent casting defects such as coarse grains, casting segregation, loose grain boundaries, and shrinkage cavities. Although the matrix has good plasticity, the grain boundary bearing capacity is weak. Direct extrusion crystallization is insufficient and fails to effectively refine the grains. At the same time, the dislocations generated by extrusion deformation are prone to recovery and annihilation, resulting in a significant reduction in work hardening effect. In addition, the high lithium content in the alloy, the large number of slip systems in the matrix itself, and the low deformation resistance ultimately lead to poor overall strength and hardness of the finished product.

[0070] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy, characterized in that, It includes an ultrafine α-Mg phase matrix and micron-sized β-Li phase particles embedded within it, wherein the micron-sized β-Li phase particles account for 10%-30% of the total volume of the magnesium-lithium alloy.

2. The high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy as described in claim 1, characterized in that, The average particle size of the ultrafine α-Mg phase is 20-200 nm. The average particle size of the micron-sized β-Li phase particles is 5-1000 μm.

3. The high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy as described in claim 1, characterized in that, The high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy has a compressive strength of 472-660 MPa and a fracture strain of 5.4-24.3%.

4. A method for preparing a high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy according to any one of claims 1-3, characterized in that, Includes the following steps: Magnesium-based powder was ball-milled to obtain nanocrystalline magnesium-based powder A. Magnesium-lithium alloy was crushed to obtain β-Li phase magnesium-lithium alloy powder B. Nanocrystalline magnesium-based powder A was mixed with β-Li phase magnesium-lithium alloy powder B to obtain mixed powder C; High-strength and tough dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy is obtained by vacuum hot pressing and plastic deformation of mixed powder C.

5. The method for preparing the high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy as described in claim 4, characterized in that, The magnesium-based powder is pure magnesium powder or magnesium alloy powder, and the purity of the magnesium-based powder is ≥99.9%. The ball milling process involves a ball-to-material mass ratio of (10-30):1, a milling time of 10-100 h, a milling speed of 200-500 r / min, and an inert gas atmosphere. A process control agent is also added during the milling process, with an addition amount of 0.5-1.5 wt.%. The process control agent includes stearic acid and sodium stearate.

6. The method for preparing the high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy as described in claim 4, characterized in that, The mass fraction of lithium in the magnesium-lithium alloy is 10.3%-15%; The crushing process is mechanical crushing or pneumatic crushing, and the crushing atmosphere is an inert gas atmosphere.

7. The method for preparing the high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy as described in claim 4, characterized in that, The volume ratio of the nanocrystalline magnesium-based powder A to the β-Li phase magnesium-lithium alloy powder B is (70-90):(10-30); the mixing time is 1-3 hours. The average particle size of the nanocrystalline magnesium-based powder A is <100 nm; The average particle size of the β-Li phase magnesium-lithium alloy powder B is 5-1000 μm.

8. The method for preparing the high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy as described in claim 4, characterized in that, The vacuum hot pressing forming temperature is 100-500℃, the pressure is 200-600MPa, and the heat and pressure holding time is 1-4 h.

9. The method for preparing the high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy as described in claim 4, characterized in that, The temperature of the plastic deformation process is 200-450℃, the extrusion ratio is (10-40):1, and the deformation amount per pass is 10%-50%.

10. The application of a high-strength and high-toughness dual-phase heterogeneous ultrafine-grained magnesium-lithium alloy according to any one of claims 1-3 in aerospace and transportation.

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