Lightweight super-elastic titanium alloy single crystal and preparation method thereof

Abstract

The invention discloses a light-weight super-elastic titanium alloy single crystal and a preparation method thereof, the light-weight super-elastic titanium alloy single crystal comprises the following alloy components in atomic percent: TiaAlbMnc, a is more than or equal to 60 and less than or equal to 85, b is more than or equal to 10 and less than or equal to 30, c is more than or equal to 2 and less than or equal to 15, and a + b + c is equal to 100; the alloy can generate reversible phase change between austenite and martensite under stress induction, the austenite is of a body-centered cubic structure, and the martensite is of an ordered face-centered tetragonal structure. According to the Ti-Al-Mn alloy provided by the invention, by regulating and controlling the atomic proportion of Ti, Al and Mn, the alloy density is remarkably reduced while high superelasticity is realized, and a novel high-performance material with light weight and superelasticity is formed.

Description

Technical Field

[0001] This invention relates to the field of advanced metal structural materials technology, and in particular to a lightweight, superelastic titanium alloy single crystal and its preparation method. Background Technology

[0002] Hyperelastic alloys are advanced functional materials capable of undergoing a reversible martensitic phase transformation during loading / unloading, thereby generating elastic strains far exceeding those of actual metals. Among them, titanium-nickel-based shape memory alloys are currently the most widely used hyperelastic material system, achieving elastic strains of up to 7%. However, this system has a high alloy density (approximately 6.5 g / cm³). 3 This limitation restricts its application in high-end equipment fields such as aerospace where extreme weight reduction is required. Therefore, developing new alloy systems that combine low density and high elasticity has become an important research direction in the field of advanced metallic materials.

[0003] In the development of lightweight hyperelastic alloys, titanium-based alloys have attracted much attention due to their low density and good biocompatibility. However, traditional polycrystalline titanium-based hyperelastic alloys, such as Ti-Nb, Ti-Mo, and Ti-Zr alloy systems, often face the following key challenges: First, grain boundaries within polycrystalline materials are prone to becoming sources of crack initiation and propagation during cyclic phase transformations, significantly deteriorating the fatigue life and hyperelastic stability of the material. Second, while polycrystalline materials are macroscopically isotropic, their hyperelastic properties are affected by the combined effects of randomly oriented grains, preventing them from reaching the theoretically optimal values. Therefore, preparing titanium alloy single crystals is considered an effective way to eliminate the adverse effects of grain boundaries and fully unleash the intrinsic hyperelastic potential of the material.

[0004] However, the preparation of titanium alloy single crystals faces significant challenges. Titanium is chemically extremely reactive and readily reacts with commonly used oxide ceramic crucibles in its molten state at high temperatures, leading to contamination. This makes the process of preparing high-quality, large-size titanium alloy single crystals using traditional melt directional solidification techniques extremely complex, costly, and inefficient, severely hindering its engineering applications. Furthermore, the compositional design of existing titanium-based superelastic alloys still largely focuses on systems containing heavier alloying elements such as Ti-Nb and Ti-Mo, failing to fully explore the lightweight potential of these alloys.

[0005] Therefore, exploring a new method for preparing titanium alloy single crystals that can avoid complex melt processing and has a relatively simple process, and designing a new alloy system that combines lightweight and superelasticity based on reversible martensitic phase transformation, is of urgent scientific significance and engineering value for promoting the practical application of next-generation lightweight superelastic materials. Summary of the Invention

[0006] To address the above problems, the present invention provides a lightweight superelastic titanium alloy single crystal and its preparation method, which solves the technical challenges of high density of shape memory alloy elastic materials, performance degradation caused by polycrystalline structure, and complex single crystal preparation process.

[0007] According to a first aspect of the present invention, a lightweight, superelastic titanium alloy single crystal is provided, wherein the alloy composition, in atomic percentage, is: Ti a Al b Mn c , where 60 ≤ a ≤ 85, 10 ≤ b ≤ 30, 2 ≤ c ≤ 15, and a+b+c=100; The alloy is capable of undergoing a reversible phase transformation between austenite and martensite under stress-induced conditions, wherein the austenite has a body-centered cubic structure and the martensite has an ordered face-centered tetragonal structure.

[0008] In the above scheme, the body-centered cubic structure is a BCC structure, and the ordered face-centered tetragonal structure is an L10 structure.

[0009] In the above scheme, the alloy can generate a hyperelastic strain of not less than 6% under uniaxial stress.

[0010] In the above scheme, the density range of the alloy is 3.8-4.8 g / cm3.

[0011] According to a second aspect of the present invention, a method for preparing a lightweight, superelastic titanium alloy single crystal is provided, comprising the following steps: S1: The elemental raw material, expressed as an atomic percentage, is Ti. a Al b Mn c The alloy ingots are prepared by weighing in proportions of 60 ≤ a ≤ 85, 10 ≤ b ≤ 30, 2 ≤ c ≤ 15, and a+b+c=100, and then by arc melting and vacuum casting. S2: Hot rolling the ingot to obtain a sheet metal; S3: Vacuum encapsulate the substrate and then perform cyclic heat treatment to grow it into a single crystal.

[0012] In the above scheme, step S1 uses elemental raw materials with a purity of not less than 99.9%, and is repeatedly melted by electric arc more than 4 times.

[0013] In the above scheme, in step S2, the ingot is hot rolled at a high temperature of 1000-1400°C, and the reduction in each pass is controlled at 10-20%, with a total reduction of not less than 50%.

[0014] In the above scheme, step S3, the cyclic heat treatment process specifically involves: heating the encapsulated alloy to 1100-1600°C and holding it at that temperature for at least 5 minutes; then cooling it to 600-900°C at a rate of at least 2°C / min and holding it at that temperature for at least 5 minutes; then heating it to 1100-1600°C at a rate of at least 2°C / min and holding it at that temperature for at least 5 minutes; repeating this heating and cooling cycle at least 5 times.

[0015] In the above scheme, the alloy has a single-phase austenitic structure in the temperature range of 1100-1600°C, and a two-phase structure of austenite and precipitated second phase in the temperature range of 600-900°C.

[0016] In the above scheme, the single crystal obtained in step S3 is an austenitic phase along the rolling direction. <100> orientation.

[0017] The beneficial effects of this invention are: (1) The Ti-Al-Mn alloy provided by the present invention, by adjusting the atomic ratio of Ti, Al and Mn, significantly reduces the alloy density while achieving high elasticity (strain recovery rate >6%), forming a new type of high-performance material with both lightweight and superelastic properties.

[0018] (2) This invention uses a conventional hot rolling combined with vacuum cyclic heat treatment all-solid-state process to prepare Ti-Al-Mn superelastic alloy single crystals, avoiding the dependence on complex melt directional solidification technology and active crucibles in the preparation of traditional titanium alloy single crystals. This process is simple, highly operable, and can significantly reduce the preparation threshold and production cost of high-quality titanium alloy single crystals.

[0019] (3) The lightweight superelastic single crystal material prepared by this invention completely eliminates grain boundaries, thereby avoiding the adverse effects of grain boundaries on fatigue life and phase transformation stability in polycrystalline materials. This material shows great application potential in aerospace precision mechanisms (such as actuators and connectors) that pursue extreme weight reduction and high reliability, as well as in biomedical implants (such as orthopedic implants and cardiovascular stents) that have extremely high requirements for biocompatibility and fatigue life. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 Ti prepared in Example 164 Al 27 Microstructure of a single crystal of lightweight superelastic titanium alloy Mn8.

[0022] Figure 2 Ti prepared in Example 1 64 Al 27 XRD pattern of Mn8 lightweight superelastic titanium alloy single crystal.

[0023] Figure 3 Ti prepared in Example 1 64 Al 27 EBSD crystal orientation diagram of Mn8 lightweight superelastic titanium alloy single crystal.

[0024] Figure 4 Ti prepared in Example 1 64 Al 27 Stress-strain curves of Mn8 lightweight superelastic titanium alloy single crystals during uniaxial loading-unloading process.

[0025] Figure 5 Ti prepared in Example 2 71 Al 15 Mn 15 Microstructure of a lightweight, superelastic titanium alloy single crystal.

[0026] Figure 6 Ti prepared in Example 2 71 Al 15 Mn 15 XRD pattern of lightweight superelastic titanium alloy single crystal.

[0027] Figure 7 Ti prepared in Example 2 71 Al 15 Mn 15 Pole diagram of the {100} crystal plane of a lightweight, superelastic titanium alloy single crystal.

[0028] Figure 8 Ti prepared in Example 2 71 Al 15 Mn 15 Stress-strain curves of lightweight, superelastic titanium alloy single crystals during uniaxial loading-unloading process.

[0029] Figure 9 Ti prepared in Example 3 83 Al 13 Microstructure of a single crystal of lightweight superelastic titanium alloy Mn4.

[0030] Figure 10 Ti prepared in Example 3 83 Al 13 XRD pattern of Mn4 lightweight superelastic titanium alloy single crystal.

[0031] Figure 11 Ti prepared in Example 3 83 Al 13 Pole diagram of the {100} crystal plane of a single crystal of lightweight superelastic titanium alloy Mn4.

[0032] Figure 12 The stress-strain curve of the lightweight hyperelastic titanium alloy single crystal prepared in Example 3 during the uniaxial loading-unloading process.

[0033] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0034] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0035] The terms "first," "second," etc., used in this disclosure are for distinguishing similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented, for example, in orders other than those illustrated or described herein.

[0036] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0037] Multiple, including two or more.

[0038] And / or, it should be understood that, for the purposes of this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0039] According to a first aspect of the present invention, a lightweight, superelastic titanium alloy single crystal is provided, wherein the alloy composition, by atomic percentage, is: Ti a Al b Mn c, where 60 ≤ a ≤ 85, 10 ≤ b ≤ 30, 2 ≤ c ≤ 15, and a+b+c=100.

[0040] In titanium alloys and the theory of martensitic phase transformation, the valence electron concentration (e / a, i.e., the average number of valence electrons per atom) is a key parameter determining the relative stability of austenite (BCC) and martensite (L10) and the martensitic phase transformation initiation temperature (Ms point). Since Ti, Al, and Mn have different valence electron numbers (Ti = 4, Al = 3, Mn = 7), and the e / a values ​​for Ti (60-85), Al (10-30), and Mn (2-15) precisely lock the e / a value of the alloy system within a specific range (typically between 4.0 and 4.3). This range is precisely the critical interval within which the BCC structure can undergo stress-induced shear transformation into an ordered L10 structure. If e / a is too low, the driving force for martensitic phase transformation is insufficient, making it difficult to induce superelasticity; if e / a is too high, the martensite is too stable and cannot revert back to austenite after unloading (i.e., it lacks thermoelasticity).

[0041] Furthermore, the ratio of Al to Mn content directly determines the tetragonality (c / a axis ratio) of L10 martensite. Only when the Al and Mn ratio makes the c / a axis ratio of the L10 structure approach a specific value (usually close to or slightly less than 1) does the lattice distortion energy generated by the phase transformation be minimized, and a fully coherent or semi-coherent interface is formed with the BCC parent phase under specific orientations (such as KS or NW relationships). When the c / a axis ratio is within this range, the volume change before and after the phase transformation is minimal (close to zero volume change), which is the geometric essence of good thermoelasticity. If the Mn content is too low, the tetragonality is insufficient, and the martensite is unstable; if the Mn content is too high, the tetragonality is too large, and interface movement will produce a large number of irreversible defects. Therefore, the composition range of Al and Mn is to pursue the geometric condition of "lattice-invariant plane strain," which is the geometric basis of the reversible phase transformation of martensite. Furthermore, controlling the Al content at 10-30% ensures that an ordered L10 structure can be formed after the austenite transforms into martensite. The emergence of an ordered structure significantly increases the critical shear stress (CRSS) for dislocation slip. Mn, as a β-stabilizing element, is dissolved in the matrix, further strengthening the parent phase and suppressing irreversible plastic deformation. This results in a phase transformation critical stress much lower than the dislocation slip critical stress. This means that under uniaxial tension / compression, the material preferentially generates strain greater than 6% through reversible phase transformations, rather than through slip that creates permanent defects. If the composition deviates, for example, if Al is too low, a stable ordered structure cannot be formed, dislocation slip will occur before the phase transformation, and hyperelasticity will disappear. Furthermore, the addition of Mn is not only for adjusting electron concentration but also for controlling stacking fault energy, reducing interfacial frictional work during the phase transformation process. This makes the loading and unloading curves almost coincide, achieving a completely reversible phase transformation. This is a key kinetic guarantee for achieving ultra-high fatigue life. If the Mn content is too low, the energy reduction is not significant; if the Mn content is too high, it may introduce a brittle second phase or reduce thermal hysteresis performance.

[0042] In this invention, the alloy can undergo a reversible phase transformation between austenite and martensite under stress-induced conditions, wherein the austenite has a body-centered cubic structure and the martensite has an ordered face-centered tetragonal structure.

[0043] Specifically, the body-centered cubic (BCC) structure and the ordered face-centered tetragonal (FCT) structure are both L10 structures. The phase transition in the L10 structure, due to the ordered atomic arrangement and tight packing, is often accompanied by small volume changes, resulting in good thermoelasticity during the phase transition. This means that the phase transition can be completely reversed back to austenite upon cooling or unloading, thus achieving fully reversible hyperelasticity. The BCC and L10 structures exhibit good lattice matching under specific orientations, making the interface movement during the phase transition reversible and stable, reducing lattice defects generated in each cycle. For single-crystal materials, this translates to extremely high fatigue life.

[0044] The alloy can exhibit hyperelastic strain of no less than 6% under uniaxial stress. This is because the alloy undergoes a reversible phase transformation between austenite and martensite under stress-induced stress. The single-crystal structure eliminates the obstacle of grain boundaries to the phase transformation, fully utilizing the material's intrinsic deformation capacity. Therefore, it exhibits hyperelastic strain.

[0045] The density of the alloy ranges from 3.8 to 4.8 g / cm³. 3 Compared to traditional NiTi-based hyperelastic alloys (density ≈ 6.5 g / cm³), 3 This alloy has a density reduction of approximately 30-40%, which offers significant advantages in weight-sensitive applications such as aerospace and medical devices.

[0046] According to a second aspect of the present invention, a method for preparing a lightweight, superelastic titanium alloy single crystal is provided, comprising the following steps: S1: The elemental raw material, expressed as an atomic percentage, is Ti. a Al b Mn c The alloy ingots are prepared by weighing in proportions of 60 ≤ a ≤ 85, 10 ≤ b ≤ 30, 2 ≤ c ≤ 15, and a+b+c=100, and then by arc melting and vacuum casting. S2: Hot rolling the ingot to obtain a sheet metal; S3: Vacuum encapsulate the substrate and then perform cyclic heat treatment to grow it into a single crystal.

[0047] In step S1, a pure elemental raw material with a purity of not less than 99.9% is used and the material is repeatedly melted by electric arc more than 4 times.

[0048] In step S2, the ingot is hot-rolled at a high temperature of 1000–1400°C, with each pass's reduction controlled at 10–20%, and the total reduction not less than 50%. Hot rolling within this temperature range avoids the risk of uneven deformation or cracking due to biphasic deformation. The BCC structure exhibits excellent plasticity at high temperatures, and temperatures above 1000°C significantly reduce the material's deformation resistance, making large reduction rolling possible while reducing mill load and die wear. Furthermore, the upper limit is controlled at 1400°C to prevent excessively high temperatures from causing grain boundary melting (overheating) or severe oxidation and peeling, ensuring the alloy's purity and machinability. Controlling the reduction per pass effectively introduces sufficient dislocation density, inducing dynamic recrystallization during high-temperature deformation. Dynamic recrystallization can refine grains and homogenize the microstructure, while releasing some internal stress. This prevents the plate from cracking due to stress concentration and ensures that deformation penetrates evenly from the surface to the core, avoiding the texture gradient difference of "large surface deformation and small core deformation". This lays the foundation for obtaining uniform single crystal orientation in the future.

[0049] A total reduction of at least 50% signifies that the alloy has undergone intense plastic deformation, accumulating a high density of crystal defects such as dislocations and vacancies. These defects store a significant amount of deformation energy, which is the core driving force for grain growth and abnormal grain development during subsequent cyclic heat treatment. If the total reduction is too low, the deformation energy is insufficient, resulting in slow grain boundary migration during subsequent heat treatment, making it difficult to break through the critical nucleus size, ultimately leading to a fine-grained structure rather than single crystal growth. Furthermore, ingots obtained from arc melting and suction casting often exhibit coarse columnar or dendritic segregation. A large deformation of 50% or more can effectively break up these as-cast structures, eliminate compositional segregation, and make the alloy elements more uniformly distributed, providing a compositional basis for the uniform growth of subsequent single crystals.

[0050] In step S3, the cyclic heat treatment process is as follows: the encapsulated alloy is heated to 1100-1600°C and held for at least 5 minutes; then cooled to 600-900°C at a rate of at least 2°C / min and held for at least 5 minutes; then heated to 1100-1600°C at a rate of at least 2°C / min and held for at least 5 minutes; this heating and cooling cycle is repeated at least 5 times.

[0051] The alloy has a single-phase austenitic structure in the temperature range of 1100-1600°C, and a two-phase structure of austenite and precipitated second phase in the temperature range of 600-900°C.

[0052] This invention completely bypasses the melt treatment stage. It induces grain growth in the solid state through hot rolling and heat treatment, fundamentally eliminating the possibility of contamination caused by the reaction of the high-temperature melt with the crucible. This eliminates the reliance on expensive special crucibles or complex directional solidification equipment, significantly lowering the technical threshold and production costs. During this repeated heating and cooling cycle, when heated from a low temperature to a high temperature again, the precipitated second phase undergoes re-dissolution. This process is equivalent to "cleaning" and "activating" the grain boundaries. Each cycle eliminates grains unfavorable to growth, allowing a grain with a dominant orientation to "grown abnormally," ultimately engulfing all other grains to form a single crystal.

[0053] The single crystal obtained in step S3 is austenitic along the rolling direction. <100> Orientation. In the BCC structure, <100> The direction is the edge direction of the unit cell. When BCC austenite transforms into L10 martensite, the crystal lattice undergoes specific distortions (such as elongation or shortening of crystal axes). For Ti-Al-Mn alloys, the maximum lattice deformation (i.e., theoretical transformation strain) corresponding to this phase transformation often occurs precisely during... <100> In the direction. When the stress is along <100> When oriented, the direction of the work done by the external force is completely aligned with the direction of lattice shear in the crystal, thus inducing martensitic phase transformation with the highest efficiency and achieving the maximum macroscopic recoverable strain. This is the fundamental reason for the ultra-high elasticity of titanium alloys. If the orientation deviates... <100> If the phase transition strain is wasted on the geometric projection inside the crystal, the macroscopically exhibited hyperelasticity will be greatly reduced.

[0054] This embodiment provides a component of Ti 64 Al 27 Lightweight superelastic titanium alloy single crystal of Mn8 (atomic percentage) and its preparation method.

[0055] The specific steps are as follows: Use elemental Ti, Al, and Mn raw materials with a purity of not less than 99.9%, and according to the atomic percentage of Ti... a Al b Mn c The raw materials are weighed in a ratio where 60 ≤ a ≤ 85, 10 ≤ b ≤ 30, 2 ≤ c ≤ 15, and a+b+c=100. The raw materials are repeatedly melted more than four times using electric arc melting, and then vacuum casting is used to prepare materials with dimensions of 15×15×100mm. 3 Alloy ingot; hot rolling the ingot at 1000°C, with each pass reducing the amount by 10% and the total reduction by 75%, to obtain a sheet; vacuum sealing the sheet, followed by cyclic heat treatment to grow it into a single crystal.

[0056] The specific cyclic heat treatment process used is as follows: the encapsulated alloy is heated to 1100°C and held for 10 minutes; then cooled to 600°C at a rate of 2°C / min and held for 5 minutes; then heated to 1100°C at a rate of 2°C / min and held for 5 minutes; this heating and cooling cycle is repeated 10 times.

[0057] Metallographic features of the prepared samples Figure 1 As shown, the prepared sample exhibits a single-phase composition, and no grain boundaries were observed, indicating that a single crystal was successfully obtained. The sample XRD pattern is shown below. Figure 2 As shown, this single crystal is an austenitic phase with a BCC structure at room temperature. The sample exhibits EBSD along the rolling direction as follows: Figure 3 As shown, the phase along the rolling direction is austenitic. <100> Orientation. For example... Figure 4The uniaxial loading-unloading stress-strain curves shown indicate that the alloy single crystal produced a fully recoverable strain of no less than 7.6% under stress, exhibiting excellent superelasticity.

[0058] Example 2: This embodiment provides a component of Ti 71 Al 15 Mn 15 Lightweight superelastic titanium alloy single crystals (atomic percentage) and their preparation methods.

[0059] The specific steps are as follows: Using elemental Ti, Al, and Mn raw materials with a purity of not less than 99.9%, weigh them according to the atomic ratio of Example 1; repeatedly melt the raw materials more than 4 times using electric arc melting, and then prepare materials with dimensions of 15×15×100mm using vacuum casting. 3 Alloy ingot; the ingot is hot rolled at 1300°C, with each pass reducing the amount by 20% and the total reduction by 80%, to obtain a sheet; the sheet is vacuum-sealed and then subjected to cyclic heat treatment to grow it into a single crystal.

[0060] The specific cyclic heat treatment process used is as follows: the encapsulated alloy is heated to 1300°C and held for 10 min; then cooled to 700°C at a rate of 5°C / min and held for 10 min; then heated to 1300°C at a rate of 5°C / min and held for 10 min; this heating and cooling cycle is repeated 8 times.

[0061] Metallographic features of the prepared samples Figure 5 As shown, the prepared sample exhibits a single-phase composition, and no grain boundaries were observed, indicating that a single crystal was successfully obtained. The sample XRD pattern is shown below. Figure 6 As shown, this single crystal is an austenitic phase with a BCC structure at room temperature. Pole diagram analysis of the sample ( Figure 7 The results show that the {100} crystal plane poles exhibit a sharp, non-dispersive, symmetrical distribution, which directly proves that the material has a single crystallographic orientation, i.e., a single crystal has been successfully prepared, and the austenite phase of this single crystal is along the rolling direction. <100> Orientation. For example... Figure 8 The uniaxial loading-unloading stress-strain curves shown indicate that the alloy single crystal produced a fully recoverable strain of no less than 6.4% under stress, exhibiting excellent superelasticity.

[0062] Example 3: This embodiment provides a component of Ti 83 Al 13 Lightweight superelastic titanium alloy single crystal of Mn4 (atomic percentage) and its preparation method.

[0063] The specific steps are as follows: Using elemental Ti, Al, and Mn raw materials with a purity of not less than 99.9%, weigh them according to the atomic ratio of Example 1; repeatedly melt the raw materials more than 4 times using electric arc melting, and then prepare materials with dimensions of 15×15×100mm using vacuum casting. 3 Alloy ingot; the ingot is hot rolled at 1350°C, with each pass reducing the amount by 20% and the total reduction by 80%, to obtain a sheet; the sheet is vacuum-sealed and then subjected to cyclic heat treatment to grow it into a single crystal.

[0064] The specific cyclic heat treatment process used is as follows: the encapsulated alloy is heated to 1600°C and held for 30 min; then cooled to 900°C at a rate of 10°C / min and held for 30 min; then heated to 1600°C at a rate of 10°C / min and held for 30 min; this heating and cooling cycle is repeated 5 times.

[0065] Metallographic features of the prepared samples Figure 9 As shown, the prepared sample exhibits a single-phase composition, and no grain boundaries were observed, indicating that a single crystal was successfully obtained. The sample XRD pattern is shown below. Figure 10 As shown, this single crystal is an austenitic phase with a BCC structure at room temperature. Pole diagram analysis of the sample ( Figure 11 The results show that the {100} crystal plane poles exhibit a sharp, non-dispersive, symmetrical distribution, which directly proves that the material has a single crystallographic orientation, i.e., a single crystal has been successfully prepared, and the austenite phase of this single crystal is along the rolling direction. <100> Orientation. For example... Figure 12 The uniaxial loading-unloading stress-strain curves shown indicate that the alloy single crystal produced a fully recoverable strain of no less than 9.9% under stress, exhibiting excellent superelasticity.

[0066] The above embodiments demonstrate that by using the composition range and the "hot rolling + cyclic heat treatment" method provided by the present invention, lightweight titanium alloy single crystals with different compositions can be successfully prepared, and all single crystals exhibit superelasticity of not less than 6%, verifying the effectiveness of the technical solution and the feasibility of the composition range of the present invention.

[0067] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0068] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0069] Through the above description of the embodiments, those skilled in the art can clearly understand that the above implementation methods can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0070] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A lightweight, superelastic titanium alloy single crystal, characterized in that, The alloy composition, expressed as an atomic percentage, is: Ti a Al b Mn c , where 60 ≤ a ≤ 85, 10 ≤ b ≤ 30, 2 ≤ c ≤ 15, and a+b+c=100; The alloy is capable of undergoing a reversible phase transformation between austenite and martensite under stress-induced conditions, wherein the austenite has a body-centered cubic structure and the martensite has an ordered face-centered tetragonal structure.

2. The lightweight, superelastic titanium alloy single crystal according to claim 1, characterized in that, The body-centered cubic structure is a BCC structure, and the ordered face-centered tetragonal structure is an L10 structure.

3. The lightweight, superelastic titanium alloy single crystal according to claim 1, characterized in that, The alloy can produce a hyperelastic strain of not less than 6% under uniaxial stress.

4. The lightweight, superelastic titanium alloy single crystal according to claim 1, characterized in that, The density of the alloy ranges from 3.8 to 4.8 g / cm³. 3 .

5. A method for preparing a lightweight, hyperelastic titanium alloy single crystal as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: The elemental raw material, expressed as an atomic percentage, is Ti. a Al b Mn c The alloy ingots are prepared by weighing in proportions of 60 ≤ a ≤ 85, 10 ≤ b ≤ 30, 2 ≤ c ≤ 15, and a+b+c=100, and then by arc melting and vacuum casting. S2: Hot rolling the ingot to obtain a sheet metal; S3: Vacuum encapsulate the substrate and then perform cyclic heat treatment to grow it into a single crystal.

6. The method for preparing lightweight superelastic titanium alloy single crystals according to claim 5, characterized in that, In step S1, a pure elemental raw material with a purity of not less than 99.9% is used and repeatedly melted by electric arc more than 4 times.

7. The method for preparing lightweight hyperelastic titanium alloy single crystals according to claim 5, characterized in that, In step S2, the ingot is hot rolled at a high temperature of 1000-1400°C, with the reduction per pass controlled at 10-20% and the total reduction not less than 50%.

8. The method for preparing lightweight hyperelastic titanium alloy single crystals according to claim 5, characterized in that, In step S3, the cyclic heat treatment process specifically involves: heating the encapsulated alloy to 1100-1600°C and holding it at that temperature for at least 5 minutes; then cooling it to 600-900°C at a rate of at least 2°C / min and holding it at that temperature for at least 5 minutes; then heating it to 1100-1600°C at a rate of at least 2°C / min and holding it at that temperature for at least 5 minutes; repeating this heating and cooling cycle at least 5 times.

9. The method for preparing lightweight superelastic titanium alloy single crystals according to claim 8, characterized in that, The alloy has a single-phase austenitic structure in the temperature range of 1100-1600°C and a two-phase structure of austenite and precipitated second phase in the temperature range of 600-900°C.

10. The method for preparing lightweight superelastic titanium alloy single crystals according to claim 5, characterized in that, The single crystal obtained in step S3 is austenitic along the rolling direction. <100> orientation.

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