A high-performance magnesium-lithium alloy layered density gradient composite material and a preparation method thereof

Abstract

The application discloses a high-performance magnesium-lithium alloy layered density gradient composite material, which is obtained by sequentially loading magnesium-lithium alloy powders with three different lithium contents into a mold in a stacking distribution mode from low to high lithium content, and then performing sintering densification; and the application also provides a preparation method of the high-performance magnesium-lithium alloy layered density gradient composite material, in which Mg-3Li-1Zn, Mg-5Li-1Zn and Mg-8Li-9Al-1Zn are sequentially placed into a mold for vacuum sintering densification to obtain the high-performance magnesium-lithium alloy layered density gradient composite material. The three kinds of magnesium-lithium alloy powders are synchronously sintered and densified after being stacked and laid to form the magnesium-lithium alloy composite material with a layered structure, meanwhile, the material has a density gradient distribution in the thickness direction, the effective matching of strength and plasticity is realized, and thus the material with high strength and high plasticity is obtained.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous materials technology, specifically relating to a high-performance magnesium-lithium alloy layered density gradient composite material and its preparation method. Background Technology

[0002] Magnesium alloys, as the lightest metallic structural materials currently available, possess advantages such as high reserves, high specific strength and specific stiffness, and good electromagnetic shielding and damping properties, making them promising candidates for applications in defense, aerospace, and transportation. High-performance magnesium alloys are a key focus of my country's strategic material development. However, existing magnesium alloys suffer from a mismatch between strength and ductility, severely limiting their widespread engineering applications. Therefore, developing high-strength, high-ductility magnesium alloy preparation technologies is crucial to overcoming the bottlenecks in the industrial application of magnesium alloys in my country.

[0003] In fact, the difficulty in synergistically combining strength and ductility has long been a significant factor hindering the development of metallic structural materials, and has garnered widespread attention from researchers. Studies on laminated aluminum alloys and bimetallic composites have shown that introducing layered and gradient structures can further enhance strength while simultaneously achieving good ductility on top of the basic materials. Furthermore, numerous studies have demonstrated that layered structures play a crucial role in improving fracture toughness, damage tolerance, impact performance, damping, fatigue resistance, and enhancing the formability and ductility of other brittle materials. Therefore, if high-strength magnesium alloys and high-ductility magnesium alloys are combined using advanced composite technology to prepare magnesium alloy (Mg / Mg) layered composite materials, the complementary effects of the two / more magnesium alloys can be fully utilized, synergistically improving the ductility and strength of the magnesium alloys while maintaining lightweight properties.

[0004] Currently, the commonly used methods for preparing Mg / Mg layered composite materials include explosive bonding, diffusion welding, and rolling bonding. While explosive bonding produces materials with high interface quality, this method is inefficient and unsuitable for continuous production. It also requires advanced operational skills, making it difficult to produce thin composite plates with high surface quality, and is environmentally unfriendly. Diffusion welding offers advantages such as smooth interfaces, low residual stress, and high precision, but the high welding temperature and long welding time can easily lead to the formation of a thick diffusion layer at the interface, coarsening of the matrix structure, and the generation of micropores at the interface due to the Kirkendall effect, thus weakening the interfacial bonding strength. Rolling bonding is currently the mainstream method for preparing layered composite plates, offering advantages such as simple operation and suitability for continuous production. However, due to the significant differences in the mechanical properties of dissimilar materials, it is difficult to achieve coordinated deformation during rolling bonding, resulting in weak interfacial bonding strength. Furthermore, the strong plastic deformation generates significant residual stress, easily leading to interfacial cracking. In addition, the matrix and interface structures tend to coarsen during subsequent annealing, and Kirkendall pores can also form at the interface. Furthermore, all of the above methods require surface treatment of the composite material to remove oxide layers, etc. However, in actual operation, the surface of the material is prone to oxidation and inclusions, thus affecting the interfacial bonding strength of the composite. Clearly, current Mg / Mg layered composite materials face challenges such as low interfacial bonding strength and susceptibility to cracking during preparation. Therefore, developing novel forming technologies for Mg / Mg layered composite materials is crucial for their engineering applications.

[0005] Spark plasma sintering (SPS), as a novel powder metallurgy sintering technology, offers advantages such as uniform heating, rapid temperature rise, low sintering temperature, short sintering time, high production efficiency, fine and uniform material microstructure, and energy saving and environmental friendliness. For magnesium alloys of different compositions with similar melting points and sintering temperatures, SPS technology can be used to prepare layered magnesium alloy composites through integrated forming and simultaneous sintering of dissimilar magnesium alloy powders. This process avoids interface oxidation and inclusions in the composite material, and features a short process flow, simple operation, and high efficiency; the resulting material has a fine microstructure, and its composition and structure can be designed and easily controlled.

[0006] Therefore, there is a need to provide a method for preparing magnesium-lithium alloy layered density gradient composite materials by spark plasma sintering, so as to achieve a short process and high efficiency in preparing high-strength and high-plasticity magnesium-lithium alloys. Summary of the Invention

[0007] The technical problem to be solved by this invention is to provide a high-performance magnesium-lithium alloy layered density gradient composite material, addressing the shortcomings of the prior art. This high-performance magnesium-lithium alloy layered density gradient composite material is obtained by sequentially loading three magnesium-lithium alloy powders with different lithium contents into a mold in order of increasing or decreasing lithium content to form a stack and a density gradient distribution, followed by sintering and densification. Because the layered, gradient structure can further improve the strength of the material based on the basic material, while also achieving better plasticity, good strength and plasticity can be obtained by distributing the three magnesium-lithium alloy powders in a layered density gradient.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a high-performance magnesium-lithium alloy layered density gradient composite material, characterized in that the high-performance magnesium-lithium alloy layered density gradient composite material is obtained by loading three magnesium-lithium alloy powders with different lithium contents into a mold in order of increasing lithium content to form a stacked distribution, and then sintering and densifying them.

[0009] The high-performance magnesium-lithium alloy layered density gradient composite material of the present invention is obtained by sequentially loading three magnesium-lithium alloy powders with different lithium contents into a mold in order of increasing or decreasing lithium content to form a stack and a density gradient distribution, followed by sintering and densification. Because the layered and gradient structure can further improve the strength of the material on the basis of the basic material, while obtaining better plasticity, good strength and plasticity can be obtained by making the three magnesium-lithium alloy powders have a layered density gradient distribution.

[0010] The above-mentioned high-performance magnesium-lithium alloy layered density gradient composite material is characterized in that the three magnesium-lithium alloy powders with different lithium contents are all prepared by gas atomization, and the particle size of the three magnesium-lithium alloy powders is less than -200 mesh, and the morphology is spherical or near-spherical. The composition of the three magnesium-lithium alloy powders with different lithium contents is respectively: Mg-3Li-1Zn, Mg-5Li-1Zn, and Mg-8Li-9Al-1Zn. The magnesium-lithium alloy powder prepared by gas atomization is chosen because this method has high efficiency, low cost, and good powder quality. Spherical or near-spherical magnesium-lithium alloy powder with a particle size of less than -200 mesh is selected because the powder morphology prepared by gas atomization is spherical or near-spherical, and the particle size of the powder has a significant impact on material properties; excessively large particle sizes result in poor material properties. Therefore, powder with a particle size of less than -200 mesh is chosen. The three magnesium-lithium alloys with different compositions are used because different lithium contents result in different strengths and plasticities. Mg-3Li-1Zn is a high-strength, low-plasticity, and difficult-to-deform magnesium alloy; Mg-8Li-9Al-1Zn is a low-strength, high-plasticity magnesium alloy; and Mg-5Li-1Zn has strength and plasticity between the two. Therefore, by matching these three alloys, a high-lightweight, high-strength, and high-plasticity magnesium alloy composite material is obtained.

[0011] In this invention, Mg-3Li-1Zn represents a mixture of 3% Li and 1% Zn by mass, with the balance being Mg; Mg-5Li-1Zn represents a mixture of 5% Li and 1% Zn by mass, with the balance being Mg; and Mg-8Li-9Al-1Zn represents a mixture of 8% Li, 9% Al, and 1% Zn by mass, with the balance being Mg.

[0012] The aforementioned high-performance magnesium-lithium alloy layered density gradient composite material is characterized in that the layer thickness ratio of the three magnesium-lithium alloys with different lithium contents in the composite material is 1:1:1. Because the three magnesium-lithium alloys contribute differently to the strength and plasticity of the composite material—Mg-3Li-1Zn has high strength and low plasticity, Mg-8Li-9Al-1Zn has low strength and high plasticity, while Mg-5Li-1Zn is in the middle—this invention selects three matrix materials with equal thickness ratios to obtain a high-strength, high-plasticity magnesium-lithium alloy layered density gradient composite material. The resulting high-performance magnesium-lithium alloy layered density gradient composite material has the same thickness in each matrix, and its microstructure is fine and its composition is uniform.

[0013] In addition, the present invention provides a method for preparing high-performance magnesium-lithium alloy layered density gradient composite materials, characterized in that the method includes the following steps:

[0014] Step 1: Weigh out Mg-8Li-9Al-1Zn alloy powder, then put it into the mold, and then vibrate the mold to spread the powder evenly inside the mold to obtain a powder filling mold.

[0015] Step 2: Weigh out Mg-5Li-1Zn alloy powder, then load it into the primary powder loading mold obtained in Step 1, and then vibrate the mold to spread the powder evenly on top of the Mg-8Li-9Al-1Zn alloy powder inside the mold, thus obtaining the secondary powder loading mold.

[0016] Step 3: Weigh out Mg-3Li-1Zn alloy powder, then load it into the secondary powder loading mold obtained in Step 2, and then vibrate the mold to spread the powder evenly on the Mg-5Li-1Zn alloy powder in the mold to obtain the tertiary powder loading mold.

[0017] Step 4: Compact the powder in the three-stage powder filling mold obtained in Step 3 using the upper and lower pressure heads of the mold to obtain a mold containing the compacted powder.

[0018] Step 5: Vacuum sintering densifies the mold containing the compacted powder obtained in Step 4 to obtain a high-performance magnesium-lithium alloy layered density gradient composite material in the mold.

[0019] In this invention, the high-performance magnesium-lithium alloy layered density gradient composite material is a three-layer composite structure, and Mg-5Li-1Zn is always used as the middle layer. Therefore, either Mg-8Li-9Al-1Zn alloy powder or Mg-3Li-1Zn alloy powder can be added in step one, as long as different alloy powders are added in step three.

[0020] The above method is characterized in that the mold in step one is a graphite mold or a steel mold. In this invention, the graphite mold has low processing, preparation, and use costs, is easy to operate, and is resistant to high temperatures, but it is easily worn out and has limited pressure resistance, thus affecting the density of the final sintered sample. In contrast, the steel mold is sturdy and durable, can withstand higher pressure, and therefore can obtain materials that fully achieve the theoretical density, which is beneficial for obtaining high-performance materials. However, it is not resistant to high temperatures, is cumbersome to operate, and has high processing costs. Therefore, both types of molds have their advantages and can be selected according to actual needs.

[0021] The above method is characterized in that, if a graphite mold is used, the pressure for vacuum sintering densification is 20 MPa to 40 MPa; if a steel mold is used, the pressure for vacuum sintering densification is 20 MPa to 80 MPa. In this invention, an appropriate pressure is selected based on the suitable mold, because excessively low pressure is detrimental to the densification of the alloy powder and affects the powder sintering quality, while excessively high pressure poses safety hazards to both the mold and the equipment.

[0022] The above method is characterized in that, in step five, the vacuum sintering densification is replaced by spark plasma sintering. The spark plasma sintering process is as follows: a mold containing compacted powder is placed in a spark plasma sintering furnace and pressurized and evacuated. The mold is heated at a heating rate of 20°C / min to 40°C / min to 20°C to 60°C below the holding temperature, and then held for 1 min to 2 min. The mold is then heated at a heating rate of 10°C / min to 20°C / min to the holding temperature and held for 2 min to 9 min. After the holding period, the mold is cooled with the furnace. Once the temperature drops below 40°C, the vacuum is broken, the furnace is opened, and the sample is removed from the mold. The resulting sample is then polished and peeled to obtain a high-performance magnesium-lithium alloy layered density gradient composite material. The holding temperature is 420°C to 470°C. In this invention, excessively low heating rates lead to coarse grains and reduced material preparation efficiency, while excessively high heating rates result in a significant difference between the programmed temperature and the actual furnace temperature, affecting the sintering quality. Therefore, to balance sintering efficiency and quality, a heating rate of 20°C / min to 40°C / min is chosen to heat the material to 20°C to 60°C below the holding temperature, followed by a holding period of 1 to 2 minutes. This ensures synchronization between the programmed and actual temperatures, guaranteeing sintering quality. Then, to avoid large temperature fluctuations during the holding period due to excessively rapid heating rates, which could affect the sintering quality, a lower heating rate is chosen to heat the material to the holding temperature. Again, to balance sintering efficiency and quality, a heating rate of 10°C / min to 20°C / min is chosen to heat the material to the holding temperature and hold it. After holding, the material is cooled with the furnace until it drops below 40°C. The vacuum is then broken, the furnace is opened, and the sample is removed from the mold. The resulting sample is then polished and peeled to obtain high-quality material. This study focuses on the performance of layered density gradient magnesium-lithium alloy composites. Sintering temperature is crucial for sintering quality; lower sintering temperatures fail to allow for the formation of strong sintering necks between powder particles, hindering densification and resulting in poor material performance. Conversely, excessively high sintering temperatures can lead to overheating, the generation of large amounts of low-melting-point liquid phases, and the volatilization of Mg and Li elements, all negatively impacting alloy properties. To balance sintering efficiency and quality, a holding temperature of 420℃–470℃ is selected. The holding time at this temperature is 2–9 minutes. Shorter holding times result in insufficient element diffusion between powder particles, preventing the formation of strong sintering necks and leading to lower matrix density. Conversely, excessively long holding times increase sintering time and costs, and can cause grain growth, resulting in coarse structures and affecting material performance. Therefore, selecting an appropriate holding time is also essential to balance sintering efficiency and quality.

[0023] The method described above is characterized in that the high-performance magnesium-lithium alloy layered density gradient composite material in step five has a compressive strength of 280 MPa to 380 MPa and a compressive strain of 15% to 25%.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. This invention utilizes powder metallurgy to simultaneously sinter high-strength, low-plasticity α single-phase magnesium-lithium alloy and low-strength, high-plasticity α+β dual-phase magnesium-lithium alloy together via spark plasma sintering. During the sintering process, Zn and Li atoms in the three magnesium-lithium alloys diffuse into each other, forming diffusion zones on both sides of the α / α+β interface. These diffusion zones are conducive to the formation of gradient heterostructures in the three magnesium-lithium alloys, thereby achieving a high-performance magnesium-lithium alloy layered density gradient composite material with matching strength and plasticity.

[0026] 2. Compared with rolling composite and diffusion welding methods, the present invention omits the surface treatment process of the plate to be composited, and compared with the rolling composite method, it also omits the subsequent annealing process. Therefore, the process flow is short and the preparation efficiency is high. The three-layer layered density gradient magnesium-lithium composite material prepared by the present invention has fine grains and uniform composition in terms of microstructure, thus exhibiting excellent mechanical properties. In terms of structure, it presents a layered structure and a density gradient structure, thus achieving a better match between strength and plasticity.

[0027] 3. In this invention, magnesium-lithium alloy powder is used as raw material, and layered density gradient magnesium-lithium composite material plates are prepared by spark plasma sintering. The process is short, low-cost, efficient, simple and flexible. The resulting material has uniform composition, fine grains, fine, uniform and dense structure, no segregation, good bonding at the interface of the three matrices, no transition layer, and the material's structure and microstructure can be designed and easily controlled, exhibiting excellent strength and plasticity, improving material utilization and obtaining certain economic benefits.

[0028] 4. This invention uses spark plasma sintering to prepare layered density gradient magnesium-lithium composite material plates. The preparation method is simple, universal, and the material shape and size are easy to control, and multilayer materials can be obtained.

[0029] 5. This invention prepares heterostructures in magnesium-lithium alloys, which effectively improves the strength and plasticity of the material, and has guiding significance for achieving a balance between strength and plasticity and thus improving the overall performance of the material.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the magnesium-lithium alloy layered density gradient composite material of the present invention.

[0032] Figure 2 This is a schematic diagram of loading Mg-8Li-9Al-1Zn alloy powder into a mold in step one of the present invention.

[0033] Figure 3 This is a schematic diagram of loading Mg-5Li-1Zn alloy powder into a mold in step two of this invention.

[0034] Figure 4 This is a schematic diagram of loading Mg-3Li-1Zn alloy powder into the mold in step three of this invention.

[0035] Figure 5 This is a schematic diagram of the mold containing compacted powder obtained in step four of the present invention.

[0036] Figure 6 This is a schematic diagram of the vacuum sintering and densification of the mold containing compacted powder in step five of the present invention.

[0037] Figure 7 This is a microstructure diagram of the Mg-3Li-1Zn and Mg-5Li-1Zn interface region of the magnesium-lithium alloy layered density gradient composite material prepared in Example 1 of the present invention.

[0038] Figure 8 This is a microstructure diagram of the Mg-5Li-1Zn and Mg-8Li-9Al-1Zn interface region of the magnesium-lithium alloy layered density gradient composite material prepared in Example 1 of the present invention.

[0039] Figure 9 The diagram shows the compressive properties of the magnesium-lithium alloy layered density gradient composite materials prepared in Examples 1 to 3 of this invention. Detailed Implementation

[0040] Figure 1 This is a schematic diagram of the structure of the magnesium-lithium alloy layered density gradient composite material of the present invention. Figure 1 As can be seen from the above, the magnesium-lithium alloy layered density gradient composite material of the present invention has a three-layer structure, consisting of a Mg-8Li-9Al-1Zn layer, a Mg-5Li-1Zn layer, and a Mg-3Li-1Zn layer, in sequence.

[0041] Figure 2 This is a schematic diagram illustrating the loading of Mg-8Li-9Al-1Zn alloy powder into a mold in step one of this invention. Figure 3 This is a schematic diagram illustrating the loading of Mg-5Li-1Zn alloy powder into the mold in step two of this invention. Figure 4 This is a schematic diagram illustrating the loading of Mg-3Li-1Zn alloy powder into the mold in step three of this invention. Figure 5 This is a schematic diagram of the mold containing compacted powder obtained in step four of the present invention. Figure 6This is a schematic diagram illustrating the vacuum sintering and densification of the mold containing compacted powder in step five of this invention. Figures 2-6 As can be seen from the diagram, the present invention first loads Mg-8Li-9Al-1Zn alloy powder into a graphite mold, then vibrates the mold to spread the powder evenly inside the mold. Next, Mg-5Li-1Zn alloy powder is loaded into the mold, and the mold is vibrated again to spread the powder evenly on top of the Mg-8Li-9Al-1Zn alloy powder layer inside the mold. Then, Mg-3Li-1Zn alloy powder is loaded into the mold, and the mold is vibrated again to spread the powder evenly on top of the Mg-5Li-1Zn alloy powder layer inside the mold. The powder is then compacted using the upper and lower pressure heads of the mold. Finally, the mold containing the compacted powder is subjected to spark plasma sintering. Figure 6 The medium F and the thick arrow indicate the pressure applied to the powder during vacuum sintering densification. Figure 6 The curve with the arrow in the middle represents the pulsed current, which yields a high-performance magnesium-lithium alloy layered density gradient composite material.

[0042] Example 1

[0043] This embodiment includes the following steps:

[0044] Step 1: Weigh 6.5g of Mg-8Li-9Al-1Zn alloy powder with a particle size of less than -200 mesh, then put it into a graphite mold, and then vibrate the mold to make the powder spread evenly inside the mold, thus obtaining a one-time powder filling mold containing a layer of Mg-8Li-9Al-1Zn alloy powder.

[0045] Step 2: Weigh 6.8g of Mg-5Li-1Zn alloy powder with a particle size of less than -200 mesh, and then put it into the primary powder filling mold obtained in Step 1. Then vibrate the mold to make the powder spread evenly on the Mg-8Li-9Al-1Zn alloy powder layer in the mold, and obtain a secondary powder filling mold with Mg-8Li-9Al-1Zn / Mg-5Li-1Zn alloy powder layers.

[0046] Step 3: Weigh 7g of Mg-3Li-1Zn alloy powder with a particle size of less than -200 mesh, and then put it into the secondary powder filling mold obtained in Step 2. Then vibrate the mold to make the powder spread evenly on the Mg-5Li-1Zn alloy powder layer in the mold, and obtain the tertiary powder filling mold with Mg-8Li-9Al-1Zn / Mg-5Li-1Zn / Mg-3Li-1Zn alloy powder layers.

[0047] Step 4: Compact the powder in the three-stage powder filling mold obtained in Step 3 using the upper and lower pressure heads of the mold to obtain a mold containing the compacted powder.

[0048] Step 5: Place the mold containing the compacted powder obtained in Step 4 into a spark plasma sintering furnace, apply pressure of 20 MPa, and evacuate until the vacuum degree reaches 1 × 10⁻⁶.-1 After Pa is below 390°C, the temperature is increased to 390°C at a heating rate of 30°C / min and held for 1 min. Then, the temperature is increased to 440°C at a heating rate of 20°C / min and held for 5 min. After the holding period, the temperature is cooled with the furnace. When the temperature drops below 40°C, the vacuum is broken, the furnace is opened, and the sample is taken out of the mold. The obtained sample is polished and peeled to obtain a high-performance magnesium-lithium alloy layered density gradient composite material.

[0049] Testing revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a diameter of 40 mm and a total thickness of 9 mm, with all three alloy matrices having equal thickness. Samples for microstructure observation and performance testing were prepared using an electrical discharge wire cutting machine. Observation revealed that the microstructure of the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment is relatively dense, with fine grains, good interfacial bonding between the three layers, and no transition phase layer.

[0050] Figure 7 This is a microstructure image of the Mg-3Li-1Zn and Mg-5Li-1Zn interface region of the magnesium-lithium alloy layered density gradient composite material prepared in this embodiment. Figure 7 As can be seen from the data, the magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a tight interface bond, does not form a transition phase layer that is distinct from the two side matrices, and the matrices on both sides of the interface are relatively dense.

[0051] Figure 8 This is a microstructure image of the Mg-5Li-1Zn and Mg-8Li-9Al-1Zn interface region of the magnesium-lithium alloy layered density gradient composite material prepared in this embodiment. Figure 8 As can be seen from the figure, the magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a tight interface. Similarly, no obvious transition phase layer is formed that is distinct from the two-sided matrix. Moreover, the two-sided matrix is ​​relatively dense. Among them, the black substance in the Mg-8Li-9Al-1Zn matrix (left side of the interface) is an oxide. This is mainly because the dual-phase magnesium-lithium alloy is easy to oxidize, and oxidation occurred during the sample preparation and grinding process.

[0052] Example 2

[0053] The difference between this embodiment and Embodiment 1 is that in step five, the temperature is raised to 390°C at a heating rate of 30°C / min, then held for 1 minute, and then raised to 430°C at a heating rate of 20°C / min and held for 5 minutes. After the holding period, the temperature is cooled with the furnace.

[0054] Example 3

[0055] The difference between this embodiment and Embodiment 1 is that in step five, the temperature is raised to 390°C at a heating rate of 30°C / min, then held for 1 minute, and then raised to 450°C at a heating rate of 20°C / min and held for 5 minutes. After the holding period, the temperature is cooled with the furnace.

[0056] Figure 9 The graph shows the compressive properties of the magnesium-lithium alloy layered density gradient composite materials prepared in Examples 1 to 3 at different temperatures. Figure 9 As can be seen from the compression performance test, the magnesium-lithium alloy layered density gradient composite material prepared in Example 1 has a compressive strength of 305.33 MPa and a compressive strain close to 20%, exhibiting good strength and plasticity. The magnesium-lithium alloy layered density gradient composite material prepared in Example 2 has a compressive strength of 302.32 MPa and a compressive strain close to 21%, exhibiting good strength and plasticity. The magnesium-lithium alloy layered density gradient composite material prepared in Example 3 has a compressive strength of 306.18 MPa and a compressive strain close to 22%, exhibiting good strength and plasticity.

[0057] Example 4

[0058] This embodiment includes the following steps:

[0059] Step 1: Weigh 7g of Mg-3Li-1Zn alloy powder with a particle size of less than -200 mesh, then put it into a graphite mold, and then vibrate the mold to spread the powder evenly inside the mold, thus obtaining a one-time powder filling mold containing a layer of Mg-3Li-1Zn alloy powder.

[0060] Step 2: Weigh 6.8g of Mg-5Li-1Zn alloy powder with a particle size of less than -200 mesh, then load it into the primary powder filling mold obtained in Step 1. Vibrate the mold to spread the powder evenly on top of the Mg-3Li-1Zn alloy powder layer inside the mold, thus obtaining a secondary powder filling mold containing Mg-3Li-1Zn / Mg-5Li-1Zn alloy powder layers.

[0061] Step 3: Weigh 6.5g of Mg-8Li-9Al-1Zn alloy powder with a particle size of less than -200 mesh, and then put it into the secondary powder filling mold obtained in Step 2. Then vibrate the mold to make the powder spread evenly on the Mg-5Li-1Zn alloy powder layer in the mold, and obtain the tertiary powder filling mold with Mg-3Li-1Zn / Mg-5Li-1Zn / Mg-8Li-9Al-1Zn alloy powder layers.

[0062] Step 4: Compact the powder in the three-stage powder filling mold obtained in Step 3 using the upper and lower pressure heads of the mold to obtain a mold containing the compacted powder.

[0063] Step 5: Place the mold containing the compacted powder obtained in Step 4 into a spark plasma sintering furnace, apply pressure of 30 MPa, and evacuate until the vacuum degree reaches 1 × 10⁻⁶. -1 After Pa is below 400°C, the temperature is increased to 400°C at a heating rate of 20°C / min, and then held for 1.5 min. Then the temperature is increased to 420°C at a heating rate of 20°C / min and held for 9 min. After the holding period, the temperature is cooled with the furnace. When the temperature drops below 40°C, the vacuum is broken, the furnace is opened, and the sample is taken out of the mold. The obtained sample is polished and peeled to obtain a high-performance magnesium-lithium alloy layered density gradient composite material.

[0064] Testing revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a diameter of 40 mm and a total thickness of 9 mm, with the thicknesses of the three alloy matrices being equal.

[0065] The high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment was used to prepare samples for microstructure observation and performance testing using an electrical discharge wire cutting machine. Observation revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a relatively dense microstructure, fine grains, good interfacial bonding between the three layers, and no transition phase layer. Compression performance testing showed that the material's compressive strength reached 302.32 MPa, and the compressive strain was close to 22.11%, exhibiting good strength and plasticity.

[0066] Example 5

[0067] This embodiment includes the following steps:

[0068] Step 1: Weigh 7g of Mg-3Li-1Zn alloy powder with a particle size of less than -200 mesh, then put it into a graphite mold, and then vibrate the mold to spread the powder evenly inside the mold, thus obtaining a one-time powder filling mold containing a layer of Mg-3Li-1Zn alloy powder.

[0069] Step 2: Weigh 6.8g of Mg-5Li-1Zn alloy powder with a particle size of less than -200 mesh, then load it into the primary powder filling mold obtained in Step 1. Vibrate the mold to spread the powder evenly on top of the Mg-3Li-1Zn alloy powder layer inside the mold, thus obtaining a secondary powder filling mold containing Mg-3Li-1Zn / Mg-5Li-1Zn alloy powder layers.

[0070] Step 3: Weigh 6.5g of Mg-8Li-9Al-1Zn alloy powder with a particle size of less than -200 mesh, and then put it into the secondary powder filling mold obtained in Step 2. Then vibrate the mold to make the powder spread evenly on the Mg-5Li-1Zn alloy powder layer in the mold, and obtain the tertiary powder filling mold with Mg-3Li-1Zn / Mg-5Li-1Zn / Mg-8Li-9Al-1Zn alloy powder layers.

[0071] Step 4: Compact the powder in the three-stage powder filling mold obtained in Step 3 using the upper and lower pressure heads of the mold to obtain a mold containing the compacted powder.

[0072] Step 5: Place the mold containing the compacted powder obtained in Step 4 into a spark plasma sintering furnace, apply pressure of 40 MPa, and evacuate until the vacuum degree reaches 1 × 10⁻⁶. -1 After Pa is below 410°C, the temperature is increased to 410°C at a heating rate of 40°C / min and held for 2 min. Then, the temperature is increased to 470°C at a heating rate of 20°C / min and held for 2 min. After the holding period, the temperature is cooled with the furnace. Once the temperature drops below 40°C, the vacuum is broken, the furnace is opened, and the sample is removed from the mold. The obtained sample is then polished and peeled to obtain a high-performance magnesium-lithium alloy layered density gradient composite material.

[0073] Testing revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a diameter of 40 mm and a total thickness of 9 mm, with the thicknesses of the three alloy matrices being equal.

[0074] The high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment was used to prepare samples for microstructure observation and performance testing using an electrical discharge wire cutting machine. Observation revealed that the microstructure of the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment is relatively dense, with fine grains, good interfacial bonding between the three layers, and no transition phase layer. Compression performance testing showed that the material's compressive strength reached 337.16 MPa, and the compressive strain was close to 18.74%.

[0075] Example 6

[0076] The difference between this embodiment and embodiment 5 is that a steel mold is used and the pressure of spark plasma sintering is 20 MPa.

[0077] Testing revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a diameter of 40 mm and a total thickness of 9 mm, with the thicknesses of the three alloy matrices being equal.

[0078] The high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment was used to prepare samples for microstructure observation and performance testing using an electrical discharge wire cutting machine. Observation revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a relatively dense microstructure, fine grains, good interfacial bonding between the three layers, and no transition phase layer. Compression performance testing showed that the material has a compressive strength of 301.07 MPa and a compressive strain close to 21.47%, exhibiting good strength and plasticity.

[0079] Example 7

[0080] The difference between this embodiment and embodiment 5 is that a steel mold is used and the pressure of spark plasma sintering is 60 MPa.

[0081] Testing revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a diameter of 40 mm and a total thickness of 9 mm, with the thicknesses of the three alloy matrices being equal.

[0082] The high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment was used to prepare samples for microstructure observation and performance testing using an electrical discharge wire cutting machine. Observation revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a relatively dense microstructure, fine grains, good interfacial bonding between the three layers, and no transition phase layer. Compression performance testing showed that the compressive strength of the material reached 352.32 MPa, and the compressive strain was close to 19.11%, exhibiting good strength and plasticity.

[0083] Example 8

[0084] The difference between this embodiment and embodiment 5 is that a steel mold is used and the pressure of spark plasma sintering is 80 MPa.

[0085] Testing revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a diameter of 40 mm and a total thickness of 9 mm, with the thicknesses of the three alloy matrices being equal.

[0086] The high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment was used to prepare samples for microstructure observation and performance testing using an electrical discharge wire cutting machine. Observation revealed that the high-performance magnesium-lithium alloy layered density gradient composite material prepared in this embodiment has a relatively dense microstructure, fine grains, good interfacial bonding between the three layers, and no transition phase layer. Compression performance testing showed that the material's compressive strength reached 362.81 MPa, and the compressive strain was close to 17.01%, exhibiting good strength and plasticity.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high-performance magnesium-lithium alloy layered density gradient composite material, characterized in that, The method for preparing the high-performance magnesium-lithium alloy layered density gradient composite material includes the following steps: Step 1: Weigh out Mg-8Li-9Al-1Zn alloy powder, then put it into the mold, and then vibrate the mold to spread the powder evenly inside the mold to obtain a powder filling mold. Step 2: Weigh out Mg-5Li-1Zn alloy powder, then load it into the primary powder loading mold obtained in Step 1, and then vibrate the mold to spread the powder evenly on top of the Mg-8Li-9Al-1Zn alloy powder inside the mold, thus obtaining the secondary powder loading mold. Step 3: Weigh out Mg-3Li-1Zn alloy powder, then load it into the secondary powder loading mold obtained in Step 2, and then vibrate the mold to spread the powder evenly on the Mg-5Li-1Zn alloy powder in the mold to obtain the tertiary powder loading mold. Step 4: Compact the powder in the three-stage powder filling mold obtained in Step 3 using the upper and lower pressure heads of the mold to obtain a mold containing the compacted powder. Step 5: The mold containing compacted powder obtained in Step 4 is subjected to vacuum sintering for densification, resulting in a high-performance magnesium-lithium alloy layered density gradient composite material. The vacuum sintering densification is performed by spark plasma sintering. The spark plasma sintering process is as follows: the mold containing compacted powder is placed in a spark plasma sintering furnace and pressurized and evacuated. The temperature is increased at a rate of 20°C / min to 40°C / min to 20°C to 60°C below the holding temperature, then held for 1 to 2 minutes. Next, the temperature is increased at a rate of 10°C / min to 20°C / min to the holding temperature and held for 2 to 9 minutes. After holding, the furnace is cooled until the temperature drops below 40°C. The vacuum is then broken, the furnace is opened, and the sample is removed from the mold. The resulting sample is polished and peeled to obtain the high-performance magnesium-lithium alloy layered density gradient composite material. The holding temperature is 420°C to 470°C. The Mg-3Li-1Zn alloy powder, Mg-5Li-1Zn alloy powder, and Mg-8Li-9Al-1Zn alloy powder were all prepared by gas atomization, and the particle size was -200 mesh, and the morphology was spherical or near-spherical.

2. The high-performance magnesium-lithium alloy layered density gradient composite material according to claim 1, characterized in that, The layer thickness ratio of the three magnesium-lithium alloys with different lithium contents in the magnesium-lithium alloy layered density gradient composite material is 1:1:

1.

3. The high-performance magnesium-lithium alloy layered density gradient composite material according to claim 1, characterized in that, The mold mentioned in step one is a graphite mold or a steel mold.

4. The high-performance magnesium-lithium alloy layered density gradient composite material according to claim 3, characterized in that, If a graphite mold is used, the pressure of vacuum sintering densification is 20MPa~40MPa; if a steel mold is used, the pressure of vacuum sintering densification is 20MPa~80MPa.

5. The high-performance magnesium-lithium alloy layered density gradient composite material according to claim 1, characterized in that, The high-performance magnesium-lithium alloy layered density gradient composite material described in step five has a compressive strength of 280 MPa to 380 MPa and a compressive strain of 15% to 25%.

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