Magnesium-lithium-based multi-component memory alloy material as well as preparation method and application thereof

Abstract

The invention relates to a magnesium-lithium-based multi-component memory alloy material and a preparation method and application thereof, and relates to the technical field of cast magnesium-based alloys, and the magnesium-lithium-based multi-component memory alloy material comprises the following raw material components in percentage by weight: 50-55% of magnesium, 15-18% of lithium, 10-12% of aluminum, 2-3% of cerium and the balance of magnesium, with the total mass of the raw material components of the magnesium-lithium-based multi-component memory alloy material being 100%. Niobium: 8-10 wt%, scandium: 5-7 wt%. The magnesium-lithium-based multi-component memory alloy material prepared in the invention has excellent performances of light weight and certain strength, and also has a wide hyperelastic temperature range and excellent salt spray corrosion resistance.

Description

Technical Field

[0001] This application relates to the field of cast magnesium-based shape memory alloy technology, and in particular to a magnesium-lithium-based multi-component shape memory alloy material, its preparation method and application. Background Technology

[0002] Shape memory alloys (SMA) are special alloy materials that exhibit the shape memory effect (SME). When subjected to external pressure or temperature changes, SMAs undergo a phase transition and automatically return to their initial shape when conditions return to normal. Currently, SMAs are widely used in the medical field, aerospace, and everyday life; however, their average density is only 6-9 g / cm³. 3 However, these limitations cannot meet the demands for lightweighting. Magnesium alloys, currently the lowest density commercially available metallic structural material, have become an ideal candidate for lightweight shipbuilding due to their excellent specific strength and weight reduction potential. However, their application in marine environments has long been limited. This is because marine environments are complex and variable depending on geographical location or ocean depth. For example, the harsh polar ice-sea environment in the Arctic, with its low temperatures, ice loads, and high humidity, places stringent demands on ship materials and structures. Conventional ship materials are prone to brittle fracture and fatigue failure in the low-temperature polar environment, making it difficult to meet the requirements for continuous and safe operation of polar ships throughout the year. In some tropical marine environments, both temperature and humidity are high. The close-packed hexagonal crystal structure of magnesium alloys results in inherently insufficient corrosion resistance. In the high-temperature and high-humidity environment of ships, the surface oxide film is prone to cracking, leading to pitting corrosion, intergranular corrosion, and other failure modes. In severe cases, this can cause a rapid decline in structural strength and even safety accidents. In ship environments, such as tropical to frigid navigation, surface and deep-sea temperature differences, and high salt spray corrosion, shape memory alloys are also needed to achieve adaptive functions. However, relatively few lightweight shape memory alloys are currently used in the complex and variable marine environment. Summary of the Invention

[0003] The purpose of this application is to address the deficiency in existing technologies regarding the limited availability of lightweight shape memory alloys capable of adapting to the complex and variable marine environment. This application proposes a magnesium-lithium-based multi-component shape memory alloy material, its preparation method, and its applications. Using a certain amount of magnesium and lithium as the matrix, this application achieves lightweighting and a stable body-centered cubic (BCC) crystal structure in the magnesium-lithium-based multi-component shape memory alloy material. By compounding with certain amounts of aluminum, cerium, niobium, and scandium, the magnesium-lithium-based multi-component shape memory alloy material not only possesses excellent properties such as lightweight and a certain strength, but also exhibits a wide superelastic temperature range and superior resistance to salt spray corrosion.

[0004] In a first aspect, the magnesium-lithium-based multi-component shape memory alloy material provided in this application adopts the following technical solution: Based on the total mass of the raw material components of the magnesium-lithium-based multi-component shape memory alloy material as 100% by weight, the raw material components of the magnesium-lithium-based multi-component shape memory alloy material include: magnesium: 50-55% by weight, specifically, the content of magnesium (Mg) can be, for example, 50%, 51%, 52%, 53%, 54%, or 55% by weight; lithium: 15-18% by weight, specifically, the content of lithium (Li) can be, for example, 15% by weight. %, 16 wt%, 17 wt% or 18 wt%, Aluminum: 10-12 wt%, specifically, the content of aluminum (Al) can be, for example, 10 wt%, 11 wt% or 12 wt%, Cerium: 2-3 wt%, specifically, the content of cerium (Ce) can be, for example, 2 wt% or 3 wt%, Niobium: 8-10 wt%, specifically, the content of niobium (Nb) can be, for example, 8 wt%, 9 wt% or 10 wt%, Scandium: 5-7 wt%, specifically, the content of scandium (Sc) can be, for example, 5 wt%, 6 wt% or 7 wt%.

[0005] Through the above technical solutions, using a certain amount of magnesium and lithium as the matrix, the lightweight and stable body-centered cubic (BCC) structure of magnesium-lithium-based multi-component shape memory alloy materials are achieved. The BCC structure exhibits high strength over a wide temperature range and under large strain conditions. By compounding a certain amount of aluminum and cerium, an Al2Ce corrosion-resistant phase can be formed, which can improve the salt spray corrosion resistance of magnesium-lithium-based multi-component shape memory alloy materials. Doping with a certain proportion of niobium and scandium can suppress dislocation slip and enhance austenite stability, thereby widening the superelastic temperature window of magnesium-lithium-based multi-component shape memory alloy materials. At the same time, a certain proportion of niobium and aluminum form a high-modulus NbAl3 phase, which works synergistically with the magnesium and lithium matrix to enhance the precipitation strengthening effect. Meanwhile, cerium helps stabilize the precipitated phase and improve the stability of the shape memory effect. As a result, the magnesium-lithium-based multi-component shape memory alloy material prepared in the end can achieve a synergistic effect of high strength, high superelasticity, and corrosion resistance while maintaining a low density.

[0006] In this application, taking the total mass of the raw material components of the magnesium-lithium-based multi-component shape memory alloy material as 100% by weight, when the content of one or more substances among magnesium, lithium, aluminum, cerium, niobium, and scandium is not within the above range, the magnesium-lithium-based multi-component shape memory alloy material cannot achieve a wide superelastic temperature range and superior salt spray corrosion resistance. For example, when the magnesium content is less than 50% by weight, magnesium, as the matrix phase, has too low a content, resulting in an excessively high proportion of β phase (Mg-Li), weakened grain boundaries, decreased yield strength, and increased β phase accelerates electrochemical corrosion, reducing the corrosion resistance of the magnesium-lithium-based multi-component shape memory alloy material. When the magnesium content is greater than 55% by weight, the α phase has too high a proportion, inhibiting stress-induced martensitic phase transformation and reducing the superelastic recovery rate. For example, when the lithium content is less than 15% by weight, the reduction of β phase leads to a narrowing of the superelastic temperature range. When the lithium content is greater than 18% by weight, excess Li generates Li2O inclusions, significantly reducing salt spray resistance.

[0007] Optionally, based on the total mass of the raw material components of the magnesium-lithium-based multi-component memory alloy material as 100% by weight, the raw material components of the magnesium-lithium-based multi-component memory alloy material include: magnesium: 52-53% by weight, lithium: 17-18% by weight, aluminum: 12% by weight, cerium: 3% by weight, niobium: 8-10% by weight, and scandium: 6-7% by weight.

[0008] Through the above technical solutions, the inventors of this application have discovered, based on the above alloy composition, that by optimizing the content of magnesium, lithium, aluminum, cerium, niobium and scandium in the raw material components of the magnesium-lithium-based multi-component memory alloy material, the superelastic temperature range of the magnesium-lithium-based multi-component memory alloy material can be improved to -60 ℃ to 60 ℃. At the same time, the magnesium-lithium-based multi-component memory alloy material has a better salt spray corrosion resistance rate.

[0009] Optionally, the mass ratio of niobium to scandium is 1.5 to 1.8:1, for example, the mass ratio of niobium to scandium is 1.5:1, 1.6:1, 1.7:1 or 1.8:1.

[0010] By further limiting the mass ratio of niobium to scandium through the above technical solutions, the superelastic temperature range of magnesium-lithium-based multi-component shape memory alloy materials can be further improved, and the temperature range can be widened to -80 ℃~70 ℃.

[0011] Optionally, the mass ratio of aluminum to cerium is 4.0:1, and the average particle size of both aluminum and cerium is 100~400 mesh.

[0012] Using the above technical solution, magnesium-lithium-based multi-component shape memory alloy materials are prepared by using aluminum and cerium of a certain particle size in a specific ratio as raw materials. This can form a certain nanoscale Al2Ce corrosion-resistant phase. The nanoscale grain boundaries of the Al2Ce corrosion-resistant phase can inhibit martensite coarsening and block corrosion channels, thereby further improving the salt spray corrosion resistance of magnesium-lithium-based multi-component shape memory alloy materials.

[0013] Secondly, this application provides a method for preparing the above-mentioned magnesium-lithium-based multi-component shape memory alloy material, the method comprising the following steps: S1. Pure magnesium, pure aluminum and pure cerium are first added to a vacuum melting furnace containing a mixture of SF6 and CO2 and melted at 700~730 ℃. Then Al-Nb master alloy is added and the temperature is raised to 750~780 ℃ for the first refining. Finally, the temperature is lowered to 650~680 ℃ and pure lithium and Mg-Sc master alloy are added for the second refining. S2. After the alloy liquid after the second refining is poured, an ingot is obtained, and then the ingot is homogenized. S3. After homogenization, the ingot is subjected to solution treatment and then cooled. Then, the solution-treated ingot is subjected to aging treatment and cooled to obtain magnesium-lithium-based multi-component shape memory alloy material.

[0014] The above technical solution uses a mixture of SF6 and CO2 as a protective gas. SF6 decomposes into sulfur and fluorine atoms at high temperatures. The fluorine atoms react with magnesium to form a dense MgF2 protective film, blocking oxygen from contacting the melt and effectively inhibiting the combustion of magnesium melt. It provides local protection, especially for highly reactive elements Li and Sc. The synergy of SF6 and CO2 further enhances the density of the MgF2 protective film. A staged melting method is adopted, first melting Mg, Al, and Ce at a specific temperature. Al and Ce preferentially form the Al2Ce corrosion-resistant phase, which serves as the nucleation substrate for subsequent Nb dissolution. Li is added last to prevent volatilization. Sc has a high burn-off rate during the high-temperature refining stage and easily forms a competing reaction with Nb, thus affecting the magnesium-lithium base. The formation of multi-component shape memory alloys involves adding Al-Nb and Mg-Sc intermediate alloys to other raw materials. This improves the dispersion efficiency of the raw materials, thereby enhancing the precision of each component and resulting in a homogeneous ingot. Homogenizing the homogeneous ingot further reduces the component segregation rate, leading to a magnesium-lithium-based multi-component shape memory alloy with a wider superelastic temperature range. Solution treatment of the homogenized ingot eliminates residual micro-segregation after homogenization, ensuring uniform distribution of aging precipitates and broadening the superelastic temperature range of the magnesium-lithium-based multi-component shape memory alloy. Aging treatment of the solution-treated ingot blocks corrosion paths due to precipitates, improving the salt spray corrosion resistance of the magnesium-lithium-based multi-component shape memory alloy while simultaneously increasing its strength.

[0015] In step S1, pure magnesium, pure aluminum, and pure cerium are first added to a vacuum melting furnace containing a mixture of SF6 and CO2. If the melting is carried out at a temperature below 700 °C, the Ce will not dissolve sufficiently and will segregate, making it difficult or difficult for the Al2Ce corrosion-resistant phase to form, thus affecting the corrosion resistance of the magnesium-lithium-based multi-component shape memory alloy material. If the melting is carried out at a temperature above 730 °C, the decomposition rate of the SF6 and CO2 mixture will be greatly increased above 730 °C, deteriorating the protection of MgF2, thus causing the melt to be directly exposed to residual oxygen, triggering microcracks during hot working, resulting in a decrease in overall performance.

[0016] In step S1, an Al-Nb master alloy is added. If the temperature is raised to less than 750 °C for the first refining, insufficient Nb dissolution and diffusion will be hindered. Undissolved Nb will suppress stress-induced martensitic phase transformation and significantly reduce superelasticity. If the temperature is raised to greater than 780 °C for the first refining, the mixed gas of SF6 and CO2 will decompose more rapidly, causing microcracks during hot working.

[0017] In step S1, if the final temperature is lowered to below 650 °C and pure lithium and Mg-Sc master alloy are added for a second refining, the lithium diffusion coefficient decreases, the Li segregation region leads to insufficient β phase (BCC structure) proportion, the stress-induced martensitic phase transformation critical stress shifts, the superelastic temperature range narrows, and the superelastic performance decreases. If the final temperature is lowered to above 680 °C and pure lithium and Mg-Sc master alloy are added for a second refining, the lithium volatilization rate increases, insufficient Li causes the α phase proportion to exceed 30%, the phase transformation driving force decreases, the superelastic recovery rate decreases, and the superelastic performance is significantly reduced.

[0018] Optionally, in step S2, the homogenization treatment temperature is 680~750℃, specifically, for example, the temperature can be 680℃, 700℃, 720℃ or 750℃, and the time is 12~20 h, specifically, for example, the time can be 12 h, 14 h, 16 h, 18 h or 20 h. In a preferred embodiment, the homogenization treatment temperature is 700~720℃, and the time is 16~18 h.

[0019] By controlling the homogenization temperature at 680~750 ℃ ​​through the above technical solution, elements such as Nb, Li, and Sc can be homogenized. Homogenization of each element can reduce the critical stress fluctuation of stress-induced martensitic phase transformation and extend the temperature range to -60℃~60 ℃. At the same time, cerium diffuses fully, promoting the continuous network distribution of Al2Ce phase and improving the corrosion resistance of magnesium-lithium-based multi-component shape memory alloy materials.

[0020] Optionally, in step S1, the temperature is raised to 750~780 ℃ for the first refining, wherein the heating rate is 3~5 ℃ / min. Specifically, for example, the heating rate can be 3 ℃ / min, 4 ℃ / min or 5 ℃ / min.

[0021] By controlling the heating rate to 3~5 ℃ / min, the internal temperature gradient of the melt can be reduced, avoiding local overheating or overcooling, ensuring sufficient dissolution and diffusion of Nb, thereby stabilizing the β phase matrix, widening the superelastic temperature range, reducing the decomposition rate of the SF6 and CO2 mixed gas, reducing Nb and Sc oxidation losses, maintaining the integrity of the passivation film, and improving salt spray corrosion resistance.

[0022] Optionally, in step S3, the specific method for cooling the homogenized ingot after solution treatment is as follows: the homogenized ingot is kept at 420~440 ℃ under a protective atmosphere for 4~6 h, and then water-quenched to room temperature. The water quenching rate is 40~60 ℃ / s, wherein the protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 150~180:1.

[0023] Through the above technical solutions, the homogenized ingot can be treated at 420~440 ℃ to fully dissolve strengthening elements such as Sc and Nb, avoiding the coarsening phase from hindering the martensitic phase transformation. When the gas flow ratio of Ar to SF6 is less than 150:1, the excessive SF6 will result in an excessively thick film layer, which will peel off during cold rolling. When the gas flow ratio of Ar to SF6 is greater than 180:1, the protection will be insufficient, and oxidation will increase the weight.

[0024] Optionally, in step S3, the specific method for aging and cooling the solution-treated ingot is as follows: the solution-treated and cooled ingot is kept at 180~200 ℃ under a protective atmosphere for 12~16 h, and then air-cooled to room temperature, wherein the protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 150~180:1.

[0025] Through the above technical solutions, the solution-treated ingot can be treated at 180~200 ℃ to activate the diffusion of elements such as Sc and Nb, and precipitate Mg3Sc and Li3Nb phases, thereby broadening the superelastic temperature range. Air cooling can suppress the formation of coarsening phases. The mixed gas of Ar and SF6 can be regarded as a secondary passivation protective film. Imbalance in the gas flow ratio of the protective gas will lead to the destruction of the film continuity, thereby reducing the salt spray corrosion resistance.

[0026] Thirdly, this application provides an application of the magnesium-lithium-based multi-component shape memory alloy material described above in the field of shipbuilding.

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. The magnesium-lithium-based multi-component shape memory alloy material described in this application first uses a certain amount of magnesium and lithium as the matrix to achieve lightweighting and BCC structure. A certain proportion of niobium and scandium are then used for multi-element doping. Through multi-element doping strategy, the phase transition temperature is controlled, dislocation slip is suppressed, and phase boundary matching is strengthened, thereby widening the superelastic temperature window. At the same time, a certain amount of aluminum and cerium are compounded to form the Al2Ce corrosion-resistant phase, which can improve the salt spray corrosion resistance of the magnesium-lithium-based multi-component shape memory alloy material. Niobium and aluminum form a high-modulus NbAl3 phase, which works synergistically with the magnesium and lithium matrix to enhance the precipitation strengthening effect. Meanwhile, cerium helps stabilize the precipitated phase and improves the stability of the shape memory effect. As a result, the magnesium-lithium-based multi-component shape memory alloy material can achieve high strength, high superelasticity, and corrosion resistance while maintaining a low density. 2. The preparation method described in this application first adopts a staged melting process to obtain an ingot with uniform composition and high compositional accuracy. Then, a homogenization treatment is performed to further reduce the compositional segregation rate, thereby broadening the superelastic temperature range. Finally, solution treatment and aging treatment are performed in sequence to further broaden the superelastic temperature range of the magnesium-lithium-based multi-component shape memory alloy material, as well as improve its salt spray corrosion resistance and strength. 3. In preferred cases, by limiting the mass ratio of niobium to scandium, the superelastic temperature range of magnesium-lithium-based multi-component shape memory alloy materials can be further improved, and the temperature range can be broadened to -80 ℃~70 ℃; by limiting the particle size and mass ratio of aluminum and cerium, the salt spray corrosion resistance of magnesium-lithium-based multi-component shape memory alloy materials can be further improved. Detailed Implementation

[0028] The present application will be further described in detail below with reference to specific embodiments.

[0029] The following examples further illustrate the magnesium-lithium-based multi-component shape memory alloy material, its preparation method, and its application as described in this application. The examples are implemented based on the technical solution of this application, providing detailed implementation methods and specific operating procedures; however, the scope of protection of this application is not limited to the following examples.

[0030] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0031] Magnesium ingots: purchased from Suzhou Xinhanyuan Semiconductor Materials Co., Ltd., purity 99.99%; Aluminum powder: purchased from Shanghai Yanbei New Materials Technology Co., Ltd., specification 325 mesh; Cerium powder: purchased from Shanghai Yanbei New Materials Technology Co., Ltd., specification 100~200 mesh; Aluminum blocks: purchased from Shanghai Yanbei New Materials Technology Co., Ltd., specification 10~30mm, purity 99.99%; Cerium particles: purchased from Shanghai Yanbei New Materials Technology Co., Ltd., specification 1~10 mm; Lithium particles: purchased from Shanghai Yanbei New Materials Technology Co., Ltd., specification 3~10 mm; Al-Nb master alloy: purchased from Yanbang New Materials; Mg-Sc master alloy: purchased from Hunan Rare Earth Metal Materials Research Institute Co., Ltd. Example 1

[0032] A method for preparing a magnesium-lithium-based multi-component shape memory alloy material, the method comprising the following steps: S1. The medium-frequency induction vacuum melting furnace is powered on, and a mixture of SF6 and CO2 (SF6 to CO2 flow rate ratio of 0.05) is introduced. After 10 minutes, magnesium ingots, aluminum powder, and cerium powder are added to the medium-frequency induction vacuum melting furnace, with a vacuum degree of 3×10⁻⁶. -3 Pa was heated to 710℃ at 5℃ / min and smelted for 30 min. Then, Al-Nb master alloy was added, and the temperature was increased to 780℃ at 5℃ / min and refined for 10 min (first refining). Finally, the temperature was decreased to 680℃ at 8℃ / min, and lithium particles and Mg-Sc master alloy were added and refined for 10 min (second refining). Before casting, the alloy composition was tested. According to the mass percentage, the alloy liquid after the second refining consisted of the following: 52 wt% magnesium, 18 wt% lithium, 12 wt% aluminum, 3 wt% cerium, 9 wt% niobium, and 6 wt% scandium (the mass ratio of aluminum to cerium was 4.0:1, and the mass ratio of niobium to scandium was 1.5:1). S2. The alloy liquid after the second refining is poured to obtain an ingot, and then the ingot is homogenized at a temperature of 720°C for 18 hours. S3. The homogenized ingot is kept at 430 ℃ under a protective atmosphere for 5 h, and then water-quenched to room temperature. The water quenching rate is 50 ℃ / s. The protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 160:1. The ingot, cooled to room temperature, was held at 200 °C under a protective atmosphere for 14 h, and then air-cooled to room temperature. The protective atmosphere was a mixture of Ar and SF6 with a gas flow ratio of 180:1, to obtain a magnesium-lithium-based multi-component shape memory alloy material. Example 2

[0033] A method for preparing a magnesium-lithium-based multi-component shape memory alloy material, differing from Example 1 in that the content of the raw material components is different, and the preparation method includes the following steps: S1. The medium-frequency induction vacuum melting furnace is powered on, and a mixture of SF6 and CO2 (SF6 to CO2 flow rate ratio of 0.05) is introduced. After 10 minutes, magnesium ingots, aluminum powder, and cerium powder are added to the medium-frequency induction vacuum melting furnace, with a vacuum degree of 3×10⁻⁶. -3 Pa was heated to 710℃ at 5℃ / min and smelted for 30 min. Then, Al-Nb master alloy was added, and the temperature was increased to 780℃ at 5℃ / min and refined for 10 min (first refining). Finally, the temperature was decreased to 680℃ at 8℃ / min, and lithium particles and Mg-Sc master alloy were added and refined for 10 min (second refining). Before casting, the alloy composition was tested. According to the mass percentage, the alloy liquid after the second refining consisted of the following: 50 wt% magnesium, 18 wt% lithium, 12 wt% aluminum, 3 wt% cerium, 10 wt% niobium, and 7 wt% scandium (the mass ratio of aluminum to cerium is 4.0:1, and the mass ratio of niobium to scandium is 1.4:1). S2. The alloy liquid after the second refining is poured to obtain an ingot, and then the ingot is homogenized at a temperature of 720°C for 18 hours. S3. The homogenized ingot is kept at 430 ℃ under a protective atmosphere for 5 h, and then water-quenched to room temperature. The water quenching rate is 50 ℃ / s. The protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 160:1. The ingot, cooled to room temperature, was held at 200 °C under a protective atmosphere for 14 h, and then air-cooled to room temperature. The protective atmosphere was a mixture of Ar and SF6 with a gas flow ratio of 180:1, to obtain a magnesium-lithium-based multi-component shape memory alloy material. Example 3

[0034] A method for preparing a magnesium-lithium-based multi-component shape memory alloy material, differing from Example 1 in that the content of the raw material components is different, and the preparation method includes the following steps: S1. The medium-frequency induction vacuum melting furnace is powered on, and a mixture of SF6 and CO2 (SF6 to CO2 flow rate ratio of 0.05) is introduced. After 10 minutes, magnesium ingots, aluminum powder, and cerium powder are added to the medium-frequency induction vacuum melting furnace, with a vacuum degree of 3×10⁻⁶. -3Pa was heated to 710℃ at 5℃ / min and smelted for 30 min. Then, Al-Nb master alloy was added, and the temperature was increased to 780℃ at 5℃ / min and refined for 10 min (first refining). Finally, the temperature was decreased to 680℃ at 8℃ / min, and lithium particles and Mg-Sc master alloy were added and refined for 10 min (second refining). Before casting, the alloy composition was tested. According to the mass percentage, the alloy liquid after the second refining consisted of the following: 55 wt% magnesium, 17 wt% lithium, 12 wt% aluminum, 2 wt% cerium, 9 wt% niobium, and 5 wt% scandium (the mass ratio of aluminum to cerium is 6.0:1, and the mass ratio of niobium to scandium is 1.8:1). S2. The alloy liquid after the second refining is poured to obtain an ingot, and then the ingot is homogenized at a temperature of 720°C for 18 hours. S3. The homogenized ingot is kept at 430 ℃ under a protective atmosphere for 5 h, and then water-quenched to room temperature. The water quenching rate is 50 ℃ / s. The protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 160:1. The ingot, cooled to room temperature, was held at 200 °C under a protective atmosphere for 14 h, and then air-cooled to room temperature. The protective atmosphere was a mixture of Ar and SF6 with a gas flow ratio of 180:1, to obtain a magnesium-lithium-based multi-component shape memory alloy material. Example 4

[0035] A method for preparing a magnesium-lithium-based multi-component shape memory alloy material differs from Example 1 in that the content of the raw material components is different, and all aluminum powder is replaced with aluminum blocks, and all cerium powder is replaced with cerium particles. The preparation method includes the following steps: S1. The medium-frequency induction vacuum melting furnace is powered on, and a mixture of SF6 and CO2 (SF6 to CO2 flow rate ratio of 0.05) is introduced. After 10 minutes, magnesium ingots, aluminum blocks, and cerium particles are added to the medium-frequency induction vacuum melting furnace, with a vacuum degree of 3×10⁻⁶. -3 Pa was heated to 710℃ at 5℃ / min and smelted for 30 min. Then, Al-Nb master alloy was added, and the temperature was increased to 780℃ at 5℃ / min and refined for 10 min (first refining). Finally, the temperature was decreased to 680℃ at 8℃ / min, and lithium particles and Mg-Sc master alloy were added and refined for 10 min (second refining). Before casting, the alloy composition was tested. According to the mass percentage, the alloy liquid after the second refining consisted of the following: 55 wt% magnesium, 16 wt% lithium, 12 wt% aluminum, 2 wt% cerium, 10 wt% niobium, and 5 wt% scandium (the mass ratio of aluminum to cerium was 6.0:1, and the mass ratio of niobium to scandium was 2.0:1). S2. The alloy liquid after the second refining is poured to obtain an ingot, and then the ingot is homogenized at a temperature of 720°C for 18 hours. S3. The homogenized ingot is kept at 430 ℃ under a protective atmosphere for 5 h, and then water-quenched to room temperature. The water quenching rate is 50 ℃ / s. The protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 160:1. The ingot, cooled to room temperature, was held at 200 °C under a protective atmosphere for 14 h, and then air-cooled to room temperature. The protective atmosphere was a mixture of Ar and SF6 with a gas flow ratio of 180:1, to obtain a magnesium-lithium-based multi-component shape memory alloy material. Example 5

[0036] A method for preparing a magnesium-lithium-based multi-component shape memory alloy material differs from Example 1 in that the melting and refining conditions in step S1 are different. The preparation method includes the following steps: S1. The medium-frequency induction vacuum melting furnace is powered on, and a mixture of SF6 and CO2 (SF6 to CO2 flow rate ratio of 0.05) is introduced. After 10 minutes, magnesium ingots, aluminum powder, and cerium powder are added to the medium-frequency induction vacuum melting furnace, with a vacuum degree of 3×10⁻⁶. -3 Pa was heated to 730℃ at 5℃ / min and smelted for 20 min. Then, Al-Nb master alloy was added, and the temperature was increased to 760℃ at 3℃ / min and refined for 15 min (first refining). Finally, the temperature was decreased to 650℃ at 5℃ / min, and lithium particles and Mg-Sc master alloy were added and refined for 20 min (second refining). Before casting, the alloy composition was tested. According to the mass percentage, the alloy liquid after the second refining consisted of the following: 52 wt% magnesium, 18 wt% lithium, 12 wt% aluminum, 3 wt% cerium, 9 wt% niobium, and 6 wt% scandium (the mass ratio of aluminum to cerium was 4.0:1, and the mass ratio of niobium to scandium was 1.5:1). S2. The alloy liquid after the second refining is poured to obtain an ingot, and then the ingot is homogenized at a temperature of 720°C for 18 hours. S3. The homogenized ingot is kept at 430 ℃ under a protective atmosphere for 5 h, and then water-quenched to room temperature. The water quenching rate is 50 ℃ / s. The protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 160:1. The ingot, cooled to room temperature, was held at 200 °C under a protective atmosphere for 14 h, and then air-cooled to room temperature. The protective atmosphere was a mixture of Ar and SF6 with a gas flow ratio of 180:1, to obtain a magnesium-lithium-based multi-component shape memory alloy material. Example 6

[0037] The method is implemented in accordance with Example 1, except that in step S2, the ingot is homogenized at a temperature of 630 °C for 28 h. Example 7

[0038] The method is implemented in accordance with Example 1, except that in step S2, the ingot is homogenized at a temperature of 800 °C for 10 h. Example 8

[0039] The method is implemented in accordance with Example 1, except that in step S3, during the solution treatment and aging treatment, the mixture of Ar and SF6 with a gas flow ratio of 160:1 is replaced with a mixture of CO2 and SF6 with a gas flow ratio of 160:1. Example 9

[0040] The method is implemented in accordance with Example 1, except that in step S3, the homogenized ingot is kept at 480°C under a protective atmosphere for 4 hours, and then water-quenched to room temperature. The water quenching rate is 70°C / s, and the protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 200:1. Example 10

[0041] The method is implemented in accordance with Example 1, except that in step S3, the ingot cooled to room temperature is kept at 200°C under a protective atmosphere for 14 hours, and then air-cooled to room temperature. The protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 200:1. Example 11

[0042] The method is implemented in accordance with Example 1, except that in step S3, the ingot cooled to room temperature is kept at 200°C under a protective atmosphere for 14 hours, and then air-cooled to room temperature. The protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 120:1.

[0043] Comparative Example 1 The process was carried out in accordance with Example 1, except that the alloy composition was tested before casting, and the alloy liquid after the second refining was calculated by mass percentage as follows: 45 wt% magnesium, 22 wt% lithium, 20 wt% aluminum, 5 wt% cerium, 5 wt% niobium and 3 wt% scandium (the mass ratio of aluminum to cerium is 4.0:1, and the mass ratio of niobium to scandium is 1.7:1).

[0044] Comparative Example 2 The process was carried out in accordance with Example 1, except that the alloy composition was tested before casting, and the alloy liquid after the second refining was calculated by mass percentage as follows: 60 wt% magnesium, 10 wt% lithium, 8 wt% aluminum, 1 wt% cerium, 12 wt% niobium and 9 wt% scandium (the mass ratio of aluminum to cerium is 8.0:1, and the mass ratio of niobium to scandium is 1.3:1).

[0045] Comparative Example 3 The process was carried out in accordance with Example 1, except that all lithium was replaced with magnesium. Specifically, the alloy liquid after the second refining was composed of the following by mass percentage: 70% magnesium, 12% aluminum, 3% cerium, 9% niobium and 6% scandium (the mass ratio of aluminum to cerium was 4.0:1 and the mass ratio of niobium to scandium was 1.5:1).

[0046] Comparative Example 4 The process was carried out in accordance with Example 1, except that all aluminum was replaced with cerium. Specifically, the alloy liquid after the second refining was composed of the following by mass percentage: 52% magnesium, 18% lithium, 15% cerium, 9% niobium and 6% scandium (the mass ratio of niobium to scandium was 1.5:1).

[0047] Comparative Example 5 The process was carried out in accordance with Example 1, except that all cerium was replaced with aluminum. Specifically, the alloy liquid after the second refining was composed of the following by mass percentage: 52% magnesium, 18% lithium, 15% aluminum, 9% niobium and 6% scandium (the mass ratio of niobium to scandium was 1.5:1).

[0048] Comparative Example 6 The process was carried out in accordance with Example 1, except that all niobium was replaced with scandium. Specifically, the alloy liquid after the second refining was composed of the following by mass percentage: 52% magnesium, 18% lithium, 12% aluminum, 3% cerium, and 15% scandium (the mass ratio of aluminum to cerium was 4.0:1).

[0049] Comparative Example 7 The process was carried out in accordance with Example 1, except that all scandium was replaced with niobium. Specifically, the alloy liquid after the second refining was composed of the following by mass percentage: 52% magnesium, 18% lithium, 12% aluminum, 3% cerium, and 15% niobium (the mass ratio of aluminum to cerium was 4.0:1).

[0050] Comparative Example 8 The process was carried out in accordance with Example 1, except that in step S1, the temperature was increased to 680°C at a rate of 5°C / min, and the melting was carried out for 40 min.

[0051] Comparative Example 9 The process was carried out in accordance with Example 1, except that in step S1, the temperature was increased to 750°C at a rate of 5°C / min, and the melting was carried out for 20 min.

[0052] Comparative Example 10 The process was carried out in accordance with Example 1, except that in step S1, the temperature was increased to 730°C at a rate of 5°C / min and refined for 20 min (first refining).

[0053] Comparative Example 11 The process was carried out in accordance with Example 1, except that in step S1, the temperature was increased to 800°C at a rate of 5°C / min and refined for 10 min (first refining).

[0054] Comparative Example 12 The process was carried out in accordance with Example 1, except that in step S1, the temperature was finally lowered to 630°C at 8°C / min, and lithium particles and Mg-Sc master alloy were added for refining for 30 min (second refining).

[0055] Comparative Example 13 The process was carried out in accordance with Example 1, except that in step S1, the temperature was finally lowered to 700°C at 8°C / min, and lithium particles and Mg-Sc master alloy were added for refining for 10 min (second refining).

[0056] Test case Hyperelasticity test at different temperatures: Magnesium-lithium based multi-component shape memory alloy material with a length of 30 mm, a width of 1.5 mm, and a thickness of 1 mm was cut as a hyperelasticity test sample. In an environmental chamber, a SANS CMT5504 universal testing machine was used to conduct variable temperature tensile tests at temperatures of -80℃, -50℃, -20℃, 0℃, room temperature, 50℃, and 70℃. The material was stretched to a pre-strain of 5% or 6%, then unloaded, and the recovery strain after unloading was measured, which is the hyperelastic strain. The cycle was repeated twice, and the tensile rate was 0.5 mm / min. Mechanical property testing: A sample with a length of 30 mm, a width of 1.5 mm, and a thickness of 1 mm was cut as a mechanical property test sample. The mechanical property test was carried out at room temperature using a SANS CMT5504 universal testing machine. The mechanical properties were tensile strength and yield strength. Salt spray corrosion resistance: A neutral salt spray test was conducted according to GB / T 10125-2021, using a 5wt% sodium chloride solution, with a salt spray settling velocity of 80 cm. 2At a rate of 2 mL / h in terms of area, the temperature inside the salt spray chamber is 35 °C, the humidity is 95% RH, the pH value of the solution is 6.8, the total test time is 1800 h. After the test, the surface corrosion condition is rated according to GB / T 6461-2002. Five specimens are tested in each group, and the lowest grade is recorded. Among them, A represents the percentage of the total area occupied by metal corrosion. Grade 10 means no corrosion, grade 9 means 0 < A ≤ 0.1, grade 8 means 0.1 < A ≤ 0.25, grade 7 means 0.25 < A ≤ 0.5, grade 6 means 0.5 < A ≤ 1.0, grade 5 means 1.0 < A ≤ 2.5, grade 4 means 2.5 < A ≤ 5.0, grade 3 means 5.0 < A ≤ 10, grade 2 means 10 < A ≤ 25, grade 1 means 25 < A ≤ 50, grade 0 means 50 < A.

[0057] The superelasticity properties of the multi-component magnesium-lithium-based memory alloy materials prepared in Examples 1 to 3 were tested at different temperatures respectively. The test results are shown in Table 1. The data in Table 1 are superelasticity (%). Table 1

[0058] According to the results in Table 1, it can be seen that the superelasticity of the multi-component magnesium-lithium-based memory alloy material described in the present invention has the characteristic of a wide temperature range from -80 °C to 70 °C. Among them, in Example 3, by controlling the mass ratio of niobium to scandium to be 1.8:1, its superelasticity at room temperature reaches 5.05%, and the superelasticity is the largest at 50 °C, reaching 5.21%.

[0059] The multi-component magnesium-lithium-based memory alloy materials prepared in Examples 1 to 11 and the alloy materials prepared in Comparative Examples 1 to 13 were respectively tested for density, superelasticity at room temperature, mechanical properties and salt spray corrosion resistance. The test results are shown in Table 2. Table 2

[0060] From the results in Table 2, it can be seen that the multi-component magnesium-lithium-based memory alloy material prepared according to the specific components and contents, and the specific preparation method in this application not only has the excellent properties of light weight and certain strength, but also has high superelasticity and relatively excellent salt spray corrosion resistance; In Comparative Example 1, the content of magnesium is less than 50% by weight, and the content of lithium is greater than 18% by weight. The salt spray corrosion resistance of the prepared alloy material is significantly reduced; In Comparative Example 2, the content of magnesium is greater than 55% by weight, and the content of lithium is less than 15% by weight. The superelasticity performance of the prepared alloy material is reduced; In Comparative Examples 3 and 4, the matrix is only magnesium or lithium, and it is difficult to form a stable BCC structure. The mechanical properties of the prepared alloy materials are significantly reduced; In Comparative Example 5, cerium was replaced with aluminum, which could not form the Al2Ce corrosion-resistant phase, and the salt spray corrosion resistance of the prepared alloy material was significantly reduced. Comparative Examples 6 and 7 replaced scandium and niobium, respectively. When only scandium or niobium was doped, the ability to suppress dislocation slip and enhance austenite stability was significantly reduced, and the superelastic properties of the prepared alloy materials were significantly reduced.

[0061] The melting temperature of Comparative Example 8 was below 700 ℃, and the salt spray corrosion resistance of the alloy material prepared by it was significantly reduced. The melting temperature of Comparative Example 9 was above 730 ℃, and the superelasticity, mechanical properties and corrosion resistance of the alloy material prepared by it were all reduced. The first refining temperature of Comparative Example 10 was below 750 ℃, and the superelasticity of the alloy material prepared by it was significantly reduced. The first refining temperature of Comparative Example 11 was above 780 ℃, and the comprehensive properties of the alloy material prepared by it were significantly reduced. The second refining temperature of Comparative Example 12 was below 650 ℃, resulting in a decrease in the ultra-temperature elastic properties of the alloy material prepared therefrom. The second refining temperature of Comparative Example 13 was above 680 ℃, resulting in a significant decrease in the ultra-temperature elastic properties of the alloy material prepared therefrom.

[0062] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A magnesium-lithium based multi-component shape memory alloy material, characterized in that, Based on the total mass of the raw material components of the magnesium-lithium-based multi-component memory alloy material as 100% by weight, the raw material components of the magnesium-lithium-based multi-component memory alloy material include: magnesium: 50-55% by weight, lithium: 15-18% by weight, aluminum: 10-12% by weight, cerium: 2-3% by weight, niobium: 8-10% by weight, and scandium: 5-7% by weight.

2. The magnesium-lithium based multi-component shape memory alloy material according to claim 1, characterized in that, Based on the total mass of the raw material components of the magnesium-lithium-based multi-component memory alloy material as 100% by weight, the raw material components of the magnesium-lithium-based multi-component memory alloy material include: magnesium: 52-53% by weight, lithium: 17-18% by weight, aluminum: 12% by weight, cerium: 3% by weight, niobium: 8-10% by weight, and scandium: 6-7% by weight.

3. The magnesium-lithium based multi-component shape memory alloy material according to claim 1, characterized in that, The mass ratio of niobium to scandium is 1.5~1.8:

1.

4. The magnesium-lithium based multi-component shape memory alloy material according to claim 1, characterized in that, The mass ratio of aluminum to cerium is 4.0:1, and the average particle size of both aluminum and cerium is 100~400 mesh.

5. A method for preparing the magnesium-lithium-based multi-component shape memory alloy material according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: S1. Pure magnesium, pure aluminum and pure cerium are first added to a vacuum melting furnace containing a mixture of SF6 and CO2 and melted at 700~730℃. Then Al-Nb master alloy is added and the temperature is raised to 750~780℃ for the first refining. Finally, the temperature is lowered to 650~680℃ and pure lithium and Mg-Sc master alloy are added for the second refining. S2. The alloy liquid after the second refining is poured to obtain an ingot, and then the ingot is homogenized. S3. After homogenization, the ingot is subjected to solution treatment and then cooled. Then, the solution-treated ingot is subjected to aging treatment and cooled to obtain magnesium-lithium-based multi-component shape memory alloy material.

6. The method for preparing the magnesium-lithium-based multi-component shape memory alloy material according to claim 5, characterized in that, In step S2, the homogenization treatment is carried out at a temperature of 680~750 ℃ ​​for 12~20 h.

7. The method for preparing the magnesium-lithium-based multi-component shape memory alloy material according to claim 5, characterized in that, In step S1, the temperature is raised to 750~780 ℃ for the first refining, wherein the heating rate is 3~5 ℃ / min.

8. The method for preparing the magnesium-lithium-based multi-component shape memory alloy material according to claim 5, characterized in that, In step S3, the specific method for cooling the homogenized ingot after solution treatment is as follows: the homogenized ingot is kept at 420~440 ℃ under a protective atmosphere for 4~6 h, and then water-quenched to room temperature. The water quenching rate is 40~60℃ / s, and the protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 150~180:

1.

9. The method for preparing the magnesium-lithium-based multi-component shape memory alloy material according to claim 5, characterized in that, In step S3, the specific method for aging and cooling the solution-treated ingot is as follows: the solution-treated and cooled ingot is kept at 180~200 ℃ under a protective atmosphere for 12~16 h, and then air-cooled to room temperature, wherein the protective atmosphere is a mixture of Ar and SF6 with a gas flow ratio of 150~180:

1.

10. The application of the magnesium-lithium-based multi-component shape memory alloy material according to any one of claims 1 to 4 in the field of shipbuilding.

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