Low-density superelastic functional titanium alloy and preparation method thereof

Abstract

The invention provides a low-density super-elastic functional titanium alloy and a preparation method thereof. The titanium alloy is prepared from the following elements in percentage by mass: 4.2 to 5.0 percent of Al, 1.6 to 2.2 percent of Cr, 0.8 to 1.2 percent of Fe, 3.0 to 4.2 percent of Mo and the balance of Ti and inevitable impurity elements. The preparation method comprises the steps of alloy cast ingot smelting, forging and rolling deformation machining and annealing treatment. The alloy prepared by the invention has excellent comprehensive properties such as high damping, high work hardening rate, high strength and plasticity, solves the key problems of difficult processing, high cost and large density of the existing superelastic metal material, and has a remarkable application prospect in new-generation advanced equipment such as aerospace, ships and intelligent robots.

Description

Technical Field

[0001] The present invention relates to the technical field of advanced integrated structural and functional metallic materials, and particularly relates to a low-density superelastic functional titanium alloy and a preparation method thereof. Background Art

[0002] Integrated structural and functional metallic materials with special physical, chemical or mechanical properties such as superconductivity, hydrogen storage, superelasticity, shape memory, etc. play key high-value applications in high-tech industrial fields such as aerospace, energy, medical treatment, and electronics through their unique functional characteristics. The research and development of new integrated structural and functional metallic materials and their preparation technologies can significantly promote the development of frontier technologies such as deep space exploration, nuclear fusion, intelligent robots, and hydrogen energy, and is one of the important hot research directions in the field of new materials by domestic and international universities and research institutes.

[0003] As an integrated structural and functional metallic material with superelasticity and shape memory, nickel-titanium alloy has the advantages of high strength, fatigue resistance, corrosion resistance, etc., and is widely used in key components such as medical stents, satellite antennas, and aerospace seals. However, nickel-titanium alloy has material problems such as high density (about 6.5 g / cm 3 ), high cost, difficult processing, and biological toxicity, which limit its application scope in key fields such as medical treatment, electronics, and automobiles. Among them, the alloy contains about 55.8 wt.% of nickel element, which is the root cause of problems such as high density, high cost, and biological toxicity. At present, there is no technical method to fundamentally solve this problem. Therefore, the research and development of nickel-free superelastic functional alloy materials and their preparation technologies have significant application prospects in new equipment in key fields.

[0004] Metastable titanium alloys with martensitic phase transformation behavior also have the characteristics of low density, high specific strength, corrosion resistance, and excellent biocompatibility. Researchers have developed a series of superelastic functional alloy materials with excellent properties through the selection of alloying elements and the regulation of microstructure. Among them, Ti-Nb-Zr series metastable titanium alloys are alloys that domestic researchers focus on due to their comprehensive mechanical properties and functional characteristics such as low modulus, superelasticity, and shape memory, and the maturity of related research is high, and key applications have been achieved in fields such as aerospace, medical treatment, and electronics. However, this series of alloys usually contains a large amount of Nb element (≥15 wt.%, even ≥30 wt.%), and Nb has application defects such as high melting point (2468 °C), high density (8.6 g / cm 3 ), and high price, resulting in problems such as difficult preparation and processing, high density, and high cost of this series of alloys, which hinder their engineering applications in more fields.

[0005] It can be seen that, based on the characteristics of the allotropic transformation between α / β two phases in titanium alloys, by selecting appropriate low-density and low-cost alloying elements or reducing the addition of high-density and precious elements, the existing high-density and high-cost alloying system can be broken through. On this basis, combined with the traditional preparation and processing technology methods of titanium alloys, an easy-to-realize short-process deformation processing technology route is innovatively developed, and it is of great engineering application value to collaboratively iterate from two aspects of composition design and processing preparation to develop a new generation of superelastic functional titanium alloy materials and preparation and processing technologies. Summary of the Invention

[0006] In view of the technical problems existing in the above-mentioned background technology, the present invention proposes a low-density superelastic functional titanium alloy and its preparation method. Its concept is reasonable. Based on the β-phase stability coefficient of titanium alloy and d the electronic titanium alloy design theory, through the selection of alloying elements and short-process preparation and processing technologies, a low-density and low-cost superelastic functional titanium alloy with a recoverable strain exceeding 5% and its preparation method have been successfully developed; at the same time, this alloy has excellent comprehensive properties such as high damping, high work hardening rate, and high strength and plasticity, solving the key problems of difficult processing, high cost, and large density faced by existing superelastic metal materials, and having significant application prospects in new-generation advanced equipment such as aerospace, ships, and intelligent robots.

[0007] To solve the above technical problems, a low-density superelastic functional titanium alloy provided by the present invention is composed of the following elements in mass percentages: Al: 4.2 - 5.0%, Cr: 1.6 - 2.2%, Fe: 0.8 - 1.2%, Mo: 3.0 - 4.2%, and the balance is Ti and inevitable impurity elements.

[0008] For the low-density superelastic functional titanium alloy, wherein: the alloy in d the electronic titanium alloy design theory of and the parameter ranges are respectively ; the β-phase stability coefficient K β of the alloy has a numerical range of 0.491 ≤ K <> β ≤ 0.695.

[0009] For the low-density superelastic functional titanium alloy, wherein: the density r of the alloy is 4.6 ≤ r ≤ 4.8.

[0010] For the low-density superelastic functional titanium alloy, wherein: the recoverable strain of the alloy is greater than 5%; the damping coefficient of the alloy within 250°C - 400°C is greater than 0.01.

[0011] The low-density superelastic functional titanium alloy, wherein: the storage modulus E' of the alloy ranges from 55 GPa ≤ E' ≤ 85 GPa, and within the temperature range of 25 °C to 400 °C, the storage modulus E' does not show a rapid downward trend with the increase in temperature.

[0012] The low-density superelastic functional titanium alloy, wherein: the tensile strength of the alloy is greater than 1 GPa, the elongation is greater than 10%, and the peak value of the work hardening rate is greater than 5 GPa.

[0013] A preparation method of a low-density superelastic functional titanium alloy mainly includes the following steps: (1) Alloy ingot melting Using titanium sponge, pure aluminum particles, pure chromium flakes, pure iron particles, and aluminum-molybdenum master alloy as raw materials and proportioning them according to the designed alloy mass percentage, then mixing the proportioned raw materials evenly and repeatedly melting them using a vacuum melting furnace to obtain an alloy ingot; (2) Forging and rolling deformation processing Successively heating the alloy ingot prepared in the above step (1) to the target temperature and holding it, then performing forging shaping, medium-temperature and room-temperature rolling deformation treatments, and obtaining alloy rolling sheets; (3) Annealing treatment Putting the alloy rolling sheets obtained in the above step (2) into a heat treatment furnace at a temperature of T4 and holding for a time t4, then taking them out for rapid cooling, and subsequently polishing their surfaces to finally obtain a superelastic titanium alloy material.

[0014] The preparation method of the low-density superelastic functional titanium alloy, wherein: in the above step (1), when preparing an alloy ingot with a weight greater than or equal to 20 kg, the vacuum melting furnace selects a vacuum electron beam melting furnace or a vacuum consumable electrode melting furnace, and the number of melting times of the vacuum electron beam melting furnace is 1 - 2 times; In the above step (1), when preparing an alloy ingot with a weight less than 20 kg, the vacuum melting furnace selects a vacuum levitation melting furnace or a vacuum non-consumable melting furnace. Among them, the number of repeated melting times of the vacuum levitation melting furnace or the vacuum consumable electrode melting furnace is 2 - 4 times, while the number of repeated melting times of the vacuum non-consumable melting is 5 - 8 times, and the vacuum degree is 10 -4 Pa ~ 10 -2 Pa.

[0015] The preparation method of the low-density superelastic functional titanium alloy, wherein: in the above step (1), when repeatedly melting the alloy ingot, it is necessary to invert the ingot melted in the previous time before starting a new melting to reduce segregation and obtain an ingot with uniform composition.

[0016] The preparation method of the low-density superelastic functional titanium alloy, wherein the specific processes of forging shaping, medium-temperature and room-temperature rolling deformation treatments in the above step (2) are: (2.1)Forging and shaping Put the alloy ingot obtained in the step (1) into a heat treatment furnace at temperature T1 and keep it for time t1, then carry out forging processing, and obtain an alloy plate blank after surface grinding treatment; (2.2)Intermediate temperature rolling Put the alloy plate blank obtained in the above step (2.1) into a heat treatment furnace at temperature T2 and keep it for time t2, then carry out rolling at temperature T2, surface treatment and segmentation to obtain a primary alloy plate; (2.3)Room temperature rolling Put the primary alloy plate obtained in the above step (2.2) into a heat treatment furnace at temperature T3 and keep it for time t3, cool it and then carry out room temperature rolling treatment to obtain an alloy rolled plate.

[0017] For the preparation method of the low-density superelastic functional titanium alloy, wherein: in the forging and shaping of the step (2.1), the temperature T1 is 1050 °C to 1200 °C, the time t1 is 4 h to 8 h, and the total deformation amount is greater than or equal to 120%.

[0018] For the preparation method of the low-density superelastic functional titanium alloy, wherein: in the intermediate temperature rolling of the step (2.2), the temperature T2 is 720 °C to 850 °C, the time t2 is 2 h to 4 h, and the total deformation amount is greater than or equal to 50%.

[0019] For the preparation method of the low-density superelastic functional titanium alloy, wherein: in the room temperature rolling of the step (2.3), the temperature T3 is 580 °C to 660 °C, the time t3 is 0.2 h to 1 h. When the room temperature rolling deformation amount is greater than 20%, repeat the heat treatment at temperature T3, and the total deformation amount is greater than or equal to 60%.

[0020] For the preparation method of the low-density superelastic functional titanium alloy, wherein: in the annealing treatment of the step (3), the temperature T4 is 680 °C to 900 °C, and the time t4 is 0.5 h to 4 h.

[0021] For the preparation method of the low-density superelastic functional titanium alloy, wherein the mass percentages of the alloy ingot obtained in the step (1) are: Al: 4.2 to 5.0%, Cr: 1.6 to 2.2%, Fe: 0.8 to 1.2%, Mo: 3.0 to 4.2%, and the balance is Ti and inevitable impurity elements.

[0022] Adopting the above technical solution, the present invention has the following beneficial effects: The concept of the present invention is reasonable. When developing low-density superelastic functional titanium alloys, aiming at the close correlation between martensitic (α' and α") phase transformation and superelasticity in titanium alloys, factors such as the critical shear stress of stress-induced martensitic transformation, the start temperature and end temperature of martensitic transformation, and the start temperature and end temperature of austenitic transformation in titanium alloy systems with different stabilities were systematically analyzed. The quantitative relationship between the β-phase stability coefficient of titanium alloys and them was focused on, and the ideal numerical range of the β-phase stability coefficient for titanium alloys to undergo stress-induced martensite (especially reversible thermoelastic martensite) was summarized. At the same time, the plastic deformation mode of metastable titanium alloys is also closely related to the alloy stability, and can be predicted by d in the electronic titanium alloy design theory Md and Bo parameters. The applicant summarized the parameter value ranges of titanium alloys with stress-induced martensitic transformation effect and . Based on the β-phase stability coefficient of titanium alloys and d the electronic titanium alloy design theory, the applicant conducted exploratory research on the composition design of superelastic functional titanium alloys, combined with experimental verification of titanium alloy processing and preparation, and carried out multiple iterations of the theoretical design method. Finally, a superelastic functional titanium alloy with a recoverable strain exceeding 5% was successfully developed.

[0023] Regarding the selection of alloying elements for low-density superelastic functional titanium alloys, the applicant stepped out of the relatively mature superelastic Ti-Nb-Zr titanium alloy system, avoided high-cost, high-density, and low-β-stability Nb and Zr elements, and chose low-density α-phase stable Al elements, as well as high-β-stability Cr, Fe, and Mo elements in a different way, so as to reduce the degree of alloying of titanium alloys and further reduce the density of titanium alloys. Regarding the determination of the addition amount of alloying elements, one is based on the ideal numerical range of the β-phase stability coefficient and and parameter value ranges in the superelastic titanium alloy composition design theory; the second is that the combined addition of Cr and Fe elements is to control the precipitation of athermal ω phase, reduce the critical shear stress of stress-induced martensitic transformation, and at the same time improve the yield strength of the alloy; the third is to preferentially increase the content of Al alloying elements under the same conditions. Thus, the alloying composition of the low-density superelastic functional titanium alloy in the present invention was finally determined, that is, Al: 4.2~5.0%, Cr: 1.6~2.2%, Fe: 0.8~1.2%, Mo: 3.0~4.2%, and the balance is Ti and unavoidable impurity elements.

[0024] The low-density superelastic functional titanium alloy of the present invention, from the perspective of alloying element composition, compared with nickel-titanium alloy, the density of the present invention has decreased by more than 30%, and the cost of alloying elements has also decreased by more than 30%; compared with the commonly used titanium alloy TC4 in aviation, the density of the alloy of the present invention has increased by about 5%, but the alloying cost has decreased by 40%; compared with Ti-Nb-Zr series titanium alloys, both the density and alloying cost of the alloy of the present invention have been significantly reduced. Thus, from the perspective of alloying, the superelastic titanium alloy of the present invention with a recoverable strain exceeding 5% has great advantages in terms of density and cost.

[0025] In the preparation method of the present invention, a three-step deformation processing route is adopted. The overall idea is to, on the basis of the traditional titanium alloy processing and preparation method, by adjusting parameters such as heating temperature, holding time, and deformation amount, significantly improve the alloy deformation processing ability, obtain an ideal titanium alloy microstructure, ensure uniform deformation of the titanium alloy material, and shorten the preparation and processing process, reduce the preparation cost of the superelastic titanium alloy material in the preparation and processing, solve the key problems of difficult processing, high cost, and large density faced by existing superelastic metal materials, and have significant application prospects in new-generation advanced equipment such as aerospace, ships, and intelligent robots.

[0026] In the preparation method of the present invention, the selection of the forging shaping heating temperature and holding time is based on the processes of traditional titanium alloy homogenization treatment and cogging forging. The selection of this temperature and time ensures uniform heating of the core and surface of the alloy ingot, and the longer holding time is for the full diffusion of alloying elements to eliminate the interdendritic segregation formed during the alloy solidification process, so as to obtain a more uniform microstructure. In addition, the larger total deformation amount in this step is to reduce the deformation difference between the core and surface of the alloy ingot, so as to obtain a rectangular plate blank with uniform internal and external structures.

[0027] In the medium-temperature rolling and room-temperature rolling in the preparation method of the present invention, two rolling deformation processing methods are combined. In view of the stress-induced phase transformation characteristic of this alloy, that is, there is a mechanism of dynamic grain refinement strengthening during the deformation process, which can well shorten the preparation and processing process. Medium-temperature rolling is to reduce the plastic deformation resistance of the alloy and obtain a microstructure with a specific orientation texture; room-temperature rolling is to use more severe cold deformation of the alloy to more efficiently refine the alloy microstructure and shorten the deformation processing time. Among them, the selection of the medium-temperature rolling heating temperature takes into account the regulation of the microstructure and the function of stress relief annealing.

[0028] By using the low-density superelastic functional titanium alloy of the present invention and its preparation method, not only a superelastic material with low density and recoverable deformation exceeding 5% is obtained, but also this alloy has high tensile strength (greater than 1 GPa), good plasticity (elongation rate greater than 10%), excellent work-hardening rate (characteristic peak exceeding 5 GPa), and good damping characteristics. Thus, it can be seen that the low-density superelastic functional titanium alloy provided by the present invention has both good comprehensive mechanical properties and excellent functional characteristics, and has significant application prospects in new-generation advanced equipment such as aerospace, ships, and intelligent robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a schematic flow chart of the preparation method of the low-density superelastic functional titanium alloy of the present invention; Figure 2 It is a graph of the relationship between stress and strain of the low-density superelastic functional titanium alloy under tension-unloading in the embodiment of the present invention; Figure 3 It is a graph of the relationship between stress and strain of the low-density superelastic functional titanium alloy under room temperature tension in the embodiment of the present invention; Figure 4 It is a work-hardening curve graph of the low-density superelastic functional titanium alloy in the embodiment of the present invention; Figure 5 It is a temperature-loss factor graph of the low-density superelastic functional titanium alloy in the embodiment of the present invention; Figure 6 It is a temperature-loss modulus graph of the low-density superelastic functional titanium alloy in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The following will clearly and completely describe the technical solutions of the present invention with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0032] The following further explains the present invention in combination with specific embodiments.

[0033] A low-density superelastic functional titanium alloy provided in this embodiment is composed of the following elements in mass percentages: Al: 4.2 - 5.0%, Cr: 1.6 - 2.2%, Fe: 0.8 - 1.2%, Mo: 3.0 - 4.2%, and the balance is Ti and inevitable impurity elements.

[0034] A low-density superelastic functional titanium alloy provided by the present invention is d in the electronic titanium alloy design theory and the parameter range is ; the β-phase stability coefficient of the alloy K β The numerical range is 0.491 ≤ K β ≤ 0.695.

[0035] The density r of a low-density superelastic functional titanium alloy provided by the present invention is calculated to be 4.6 ≤ r ≤ 4.8; the recoverable strain of the alloy is greater than or equal to 5%; the damping coefficient of the alloy within 250°C - 400°C is greater than 0.01; the numerical range of the storage modulus E' of the alloy is 55 GPa ≤ E' ≤ 85 GPa, and E' does not show a rapid downward change trend with the increase of temperature within 25°C - 400°C. In addition, the tensile strength of the alloy is greater than or equal to 1 GPa, the elongation is greater than 10%, and the characteristic peak value of the work hardening rate is greater than or equal to 5 GPa. It can be seen that the low-density superelastic functional titanium alloy provided by the present invention has both excellent functional characteristics and good comprehensive mechanical properties, and has significant application prospects in new-generation advanced equipment such as aerospace, ships, and intelligent robots.

[0036] As Figure 1 shown, the preparation method of the low-density superelastic functional titanium alloy provided by the present invention mainly includes the following steps: (1) Melting and casting ingots Using titanium sponge, pure aluminum particles, pure chromium flakes, pure iron particles, and aluminum-molybdenum master alloy as raw materials, proportioning according to the designed mass percentages of the alloy, and then mixing the proportioned raw materials evenly and melting them using a vacuum melting furnace to obtain an alloy ingot, with the vacuum degree being 10 -4 Pa ~ 10 -2Pa. Regarding the selection of the melting furnace, when preparing alloy ingots with a weight of 20 kg or more, a vacuum electron beam melting furnace or a vacuum consumable electrode melting furnace can be selected. The number of melting times of the vacuum electron beam melting furnace is 1 - 2 times; when preparing alloy ingots with a weight less than 20 kg, a vacuum levitation melting furnace or a vacuum non-consumable melting furnace can be selected; among them, the number of repeated melting times n of the vacuum levitation melting furnace or the vacuum consumable electrode melting furnace is 2 - 4 times, while the number of repeated melting times n of the vacuum non-consumable melting is 5 - 8 times. When repeatedly melting alloy ingots, the ingot from the previous melting needs to be inverted to start a new melting in order to reduce segregation and obtain an ingot with uniform composition; (2) Deformation processing This step can be split into three parts. After heating the alloy material to the target temperature and holding it, forging and shaping, intermediate temperature and room temperature rolling deformation treatments are carried out in sequence, and rolled sheets are obtained. Their specific technical routes are introduced as follows: (2.1) Forging and shaping Put the alloy ingot in step (1) into a heat treatment furnace with a temperature T1 of 1050°C - 1200°C and hold it for a time t1 of 4 h - 8 h, and then carry out forging processing (which is a common forging process for titanium alloys, namely upsetting and drawing out), with the total deformation in the length, width, and height directions being greater than or equal to 120%. After surface grinding treatment, alloy sheet blanks with a square or other shape are obtained; (2.2) Intermediate temperature rolling Put the alloy sheet blank in step (2.1) into a heat treatment furnace with a temperature T2 of 720°C - 850°C and hold it for a time t2 of 2 h - 4 h, and then carry out rolling at temperature T2, with the total deformation in the thickness direction being greater than or equal to 50%. After surface treatment (referring to processing such as mechanical grinding of the surface of the rolled sheet, cutting of the edges, and removal of the oxide layer) and splitting, alloy primary sheets are obtained; (2.3) Room temperature rolling Put the alloy primary sheet in step (2.2) into a heat treatment furnace with a temperature T3 of 580°C - 660°C and hold it for a time t3 of 0.2 h - 1 h. After cooling, carry out room temperature (usually referring to 0 - 30°C) rolling treatment. When the room temperature rolling deformation is greater than 20%, repeat the heat treatment at temperature T3, with the total deformation in the thickness direction being greater than or equal to 60%, and alloy rolled sheets are obtained; (3) Annealing treatment Put the alloy rolled sheet in step (2.3) into a heat treatment furnace with a temperature T4 of 680°C - 900°C and hold it for a time t4 of 0.5 h - 4 h, take it out and carry out rapid cooling (the sample is quickly put into water for cooling), and then polish its surface to finally obtain superelastic titanium alloy materials.

[0037] The density ρ of a low-density superelastic functional titanium alloy provided by the present invention is calculated to be 4.6 ≤ ρ ≤ 4.8; the recoverable strain of the alloy is greater than or equal to 5%; within the range of 250 °C to 400 °C, the damping coefficient of the alloy is greater than or equal to 0.01; the value range of the storage modulus E' of the alloy is 55 GPa ≤ E' ≤ 85 GPa, and within the range of 25 °C to 400 °C, E' does not show a rapid downward change trend with the increase of temperature. In addition, the tensile strength of the alloy is greater than or equal to 1 GPa, the elongation is greater than 10%, and the characteristic peak value of the work hardening rate is greater than or equal to 5 GPa. It can be seen that the low-density superelastic functional titanium alloy provided by the present invention has both excellent functional characteristics and good comprehensive mechanical properties, and has significant application prospects in new-generation advanced equipment such as aerospace, ships, and intelligent robots.

[0038] Example 1:

[0039] In Example 1 of the present invention, the low-density superelastic functional titanium alloy is composed of the following elements by mass percentage: Al is 4.8%, Cr is 2.0%, Fe is 1.0%, Mo is 3.2%, and the balance is Ti and inevitable impurity elements.

[0040] The low-density superelastic functional titanium alloy provided in Example 1 of the present invention, in d the electronic titanium alloy design theory, its and parameters are 2.389 and 2.762 respectively, the β-phase stability coefficient K β value is 0.584, and its density ρ is calculated to be 4. .69.

[0041] Combined with Figure 1 the schematic process diagram of the preparation method of a low-density superelastic functional titanium alloy of the present invention shown, the predetermined mass of the melting ingot is 2 kg, and the following steps can be specifically included: (1) Melting the ingot Using titanium sponge, pure aluminum particles, pure chromium flakes, pure iron particles and aluminum-molybdenum master alloy as raw materials, proportioning according to the designed mass percentage of the alloy, mixing the raw materials evenly, and then using a vacuum levitation melting furnace to melt the alloy ingot 3 times repeatedly, the vacuum degree is 10 -3 Pa, and when melting the alloy ingot repeatedly, the head and tail of the ingot are inverted and then a new melting is started.

[0042] (2) Deformation processing This step can be split into 3 parts. After heating the alloy material to the target temperature and holding it, forging shaping, medium-temperature and room-temperature rolling deformation treatments are carried out in sequence, and rolled sheets are obtained. The specific technical routes are introduced as follows: (2.1) Forging shaping Put the alloy ingot in step (1) into a heat treatment furnace at a temperature T1 of 1150 °C and keep it for a holding time t1 of 4 h, then perform forging processing with a total deformation in the length, height, and width directions greater than 150%. After surface grinding treatment, a square alloy plate blank is obtained; (2.2) Medium-temperature rolling Put the alloy plate blank in step (2.1) into a heat treatment furnace at a temperature T2 of 750 °C and keep it for a holding time t2 of 2 h, then perform medium-temperature rolling with a total deformation in the thickness direction of 58%. After surface treatment and segmentation, an alloy primary plate is obtained; (2.3) Room-temperature rolling Put the alloy primary plate in step (2.2) into a heat treatment furnace at a temperature T3 of 600 °C and keep it for a holding time t3 of 0.5 h. After cooling, perform room-temperature rolling treatment. When the room-temperature rolling deformation is greater than 20%, repeat the heat treatment at temperature T3. The total deformation in the thickness direction is 82% to obtain an alloy rolled plate; (3) Annealing treatment Put the alloy rolled plate in step (2.3) into a heat treatment furnace at a temperature T4 of 830 °C and keep it for a holding time t4 of 1 h. Take it out and perform rapid cooling, and then polish its surface to finally obtain a superelastic titanium alloy material.

[0043] As Figures 2 - 6 shown ( Figures 2 - 6 the curve 1 in it represents the test analysis curve of Example 1), for the low-density superelastic functional titanium alloy in Example 1 of the present invention, mechanical properties and functional characteristics are tested and analyzed. The test results show that the recoverable strain of the alloy is greater than 5%, the tensile strength is 1070 MPa, the elongation is greater than 10%, and the characteristic peak value of the work hardening rate is 15.2 GPa; within 25 °C to 400 °C, the damping coefficient of the alloy is greater than 0.01 and the storage modulus E' increases slowly with the increase of temperature and slightly decreases at 380 °C. Thus, it can be seen that the low-density superelastic functional titanium alloy provided in Example 1 of the present invention has both good comprehensive mechanical properties and excellent functional characteristics.

[0044] Example 2:

[0045] The low-density superelastic functional titanium alloy in Example 2 of the present invention is composed of the following elements by mass percentage: Al is 4.2%, Cr is 1.8%, Fe is 1.0%, Mo is 4.0%, and the balance is Ti and inevitable impurity elements.

[0046] The low-density superelastic functional titanium alloy provided in Example 2 of the present invention, in d the electronic titanium alloy design theory, its and (4) The parameters are 2.391 and 2.767 respectively, and the β-phase stability coefficientK β The numerical value is 0.602, and its density r is calculated to be 4.74.

[0047] Combined Figure 1 As shown in the schematic process diagram of the preparation method of a low-density superelastic functional titanium alloy of the present invention, the mass of the predetermined smelting ingot is 5 kg, and the following steps can be specifically included: (1) Smelting the ingot Using titanium sponge, pure aluminum particles, pure chromium flakes, pure iron particles and aluminum-molybdenum master alloy as raw materials, the composition ratio is carried out according to the designed alloy mass percentage. After mixing the raw materials evenly, the alloy ingot is obtained by repeating smelting 3 times using a vacuum levitation melting furnace, and the vacuum degree is 10 -3 Pa, and when repeating the smelting of the alloy ingot, the head and tail of the ingot are inverted and then a new smelting is started.

[0048] (2) Deformation processing This step can be split into 3 parts. After heating the alloy material to the target temperature and holding it, forging shaping, medium-temperature and room-temperature rolling deformation treatments are carried out in sequence, and a rolled sheet is obtained. The specific technical routes are introduced as follows: (2.1) Forging shaping Put the alloy ingot in step (1) into a heat treatment furnace with a temperature T1 of 1160 °C and hold it for a time t1 of 4.5 h, then carry out forging processing. The total deformation in the length, height and width directions is greater than 120%. After surface grinding treatment, a square alloy sheet blank is obtained; (2.2) Medium-temperature rolling Put the alloy sheet blank in step (2.1) into a heat treatment furnace with a temperature T2 of 720 °C and hold it for a time t2 of 2 h, then carry out medium-temperature rolling. The total deformation in the thickness direction is 65%. After surface treatment and segmentation, a primary alloy sheet is obtained; (2.3) Room-temperature rolling Put the primary alloy sheet in step (2.2) into a heat treatment furnace with a temperature T3 of 620 °C and hold it for a time t3 of 0.75 h. After cooling, carry out room-temperature rolling treatment. When the room-temperature rolling deformation is greater than 20%, repeat the heat treatment at temperature T3. The total deformation in the thickness direction is 86%, and a rolled alloy sheet is obtained; (3) Annealing treatment Put the rolled alloy sheet in step (2.3) into a heat treatment furnace with a temperature T4 of 820 °C and hold it for a time t4 of 0.5 h, take it out and carry out rapid cooling, and then polish its surface to finally obtain a superelastic titanium alloy material.

[0049] As Figures 2 - 6 shown ( Figures 2 - 6The curve 2 therein represents the test curve of Example 2. For the low-density superelastic functional titanium alloy in Example 2 of the present invention, mechanical properties and functional characteristics were tested and analyzed. The test results show that the recoverable strain of this alloy is greater than 5%, the tensile strength is 1078 MPa, the elongation is greater than 10%, and the peak value of the work hardening rate characteristic is 7.3 GPa; within the range of 180 °C to 400 °C, the damping coefficient of the alloy is greater than 0.01 and the storage modulus E' increases slowly with the increase of temperature, and there is a slight decrease at 375 °C. Thus, it can be seen that the low-density superelastic functional titanium alloy provided in Example 2 of the present invention has both good comprehensive mechanical properties and excellent functional characteristics.

[0050] Example 3: The low-density superelastic functional titanium alloy in Example 3 of the present invention is composed of the following elements by mass percentage: Al is 4.5%, Cr is 2%, Fe is 1.0%, Mo is 3.5%, and the balance is Ti and inevitable impurity elements.

[0051] The low-density superelastic functional titanium alloy provided in Example 3 of the present invention, in d the electronic titanium alloy design theory, its and parameters are 2.389 and 2.765 respectively, the β-phase stability coefficient K β value is 0.602, and its density r is calculated to be 4.71.

[0052] Combined with Figure 1 the schematic flow chart of the preparation method of a low-density superelastic functional titanium alloy of the present invention shown, the predetermined mass of the melted and cast ingot is 200 kg, and the following steps can be specifically included: (1) Melting and casting the ingot Using sponge titanium, pure aluminum particles, pure chromium flakes, pure iron particles and aluminum-molybdenum master alloy as raw materials, proportioning according to the designed alloy mass percentage, mixing the raw materials evenly to prepare an electrode, and obtaining an alloy ingot after repeating melting 3 times with a vacuum consumable melting furnace. The vacuum degree is 10 -3 Pa, and when repeating melting the alloy ingot, the head and tail of the ingot are inverted and then a new melting is started.

[0053] (2) Deformation processing This step can be split into 3 parts for implementation. After heating the alloy material to the target temperature and holding it, forging and shaping, intermediate temperature and room temperature rolling deformation treatments are carried out in sequence, and rolled sheets are obtained. The specific technical routes are introduced as follows: (2.1) Forging and shaping Put the alloy ingot in step (1) into a heat treatment furnace at a temperature T1 of 1150 °C and hold for a time t1 of 6 h, then perform forging processing with a total deformation in the length, width, and height directions greater than 180%. After surface grinding treatment, a square alloy plate blank is obtained; (2.2) Medium-temperature rolling Put the alloy plate blank in step (2.1) into a heat treatment furnace at a temperature T2 of 760 °C and hold for a time t2 of 4 h, then perform medium-temperature rolling with a total deformation in the thickness direction of 90%. After surface treatment and segmentation, an alloy primary plate is obtained; (2.3) Room-temperature rolling Put the alloy primary plate in step (2.2) into a heat treatment furnace at a temperature T3 of 600 °C and hold for a time t3 of 1 h. After cooling, perform room-temperature rolling treatment. When the room-temperature rolling deformation is greater than 20%, repeat the heat treatment at temperature T3 with a total deformation in the thickness direction of 81% to obtain an alloy rolled plate; (3) Annealing treatment [[ID=,12]]Put the alloy rolled plate in step (2.3) into a heat treatment furnace at a temperature T4 of 850 °C and hold for a time t4 of 0.5 h, take it out and perform rapid cooling, and then polish its surface to finally obtain a superelastic titanium alloy material.

[0054] As Figures 2 - 6 shown ( Figures 2 - 6 the curve 3 in it represents the test analysis curve of Example 3), for the low-density superelastic functional titanium alloy in Example 3 of the present invention, mechanical properties and functional characteristics are tested and analyzed. The test results show that the recoverable strain of this alloy is greater than 5%, the tensile strength is 1115 MPa, the elongation is greater than 10%, and the characteristic peak value of the work hardening rate is 11.8 GPa; within 225 °C to 400 °C, the damping coefficient of the alloy is greater than 0.01. Thus, it can be seen that the low-density superelastic functional titanium alloy provided in Example 3 of the present invention has both good comprehensive mechanical properties and excellent functional characteristics.

[0055] The concept of the present invention is reasonable. Based on the β-phase stability coefficient of titanium alloy and d the electron titanium alloy design theory, by optimizing alloying elements and short-process preparation and processing technologies, a low-density and low-cost superelastic functional titanium alloy with a recoverable strain exceeding 5% and its preparation method are successfully developed. At the same time, this alloy has excellent comprehensive properties such as high damping, high work hardening rate, and high strength and plasticity, solving the key problems of difficult processing, high cost, and large density faced by existing superelastic metal materials, and having significant application prospects in new-generation advanced equipment such as aerospace, ships, and intelligent robots.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A low-density superelastic functional titanium alloy, characterized in that, It consists of elements in the following mass percentages: Al: 4.2 - 5.0%, Cr: 1.6 - 2.2%, Fe: 0.8 - 1.2%, Mo: 3.0 - 4.2%, and the balance is Ti and inevitable impurity elements.

2. The low-density superelastic functional titanium alloy according to claim 1, wherein: The alloy is within d in the and parameter ranges of the electronic titanium alloy design theory respectively; the β-phase stability coefficient K β of the alloy has a numerical range of 0.491 ≤ K β ≤ 0.

695.

3. The low-density superelastic functional titanium alloy according to claim 1, characterized in that: The density r of the alloy is 4.6 ≤ r ≤ 4.

8.

4. The low-density superelastic functional titanium alloy according to claim 1, characterized in that: The recoverable strain of the alloy is greater than 5%; the damping coefficient of the alloy is greater than 0.01 within the range of 250 °C - 400 °C.

5. The low-density superelastic functional titanium alloy according to claim 1, wherein: The numerical range of the storage modulus E' of the alloy is 55 GPa ≤ E' ≤ 85 GPa, and the storage modulus E' does not show a rapid downward trend with the increase of temperature within the range of 25 °C - 400 °C.

6. The low-density superelastic functional titanium alloy according to claim 1, wherein: The tensile strength of the alloy is greater than 1 GPa, the elongation is greater than 10%, and the characteristic peak value of the work hardening rate is greater than 5 GPa.

7. A preparation method of a low-density superelastic functional titanium alloy, characterized in that, It mainly includes the following steps: (1)Melting of alloy ingot Using sponge titanium, pure aluminum particles, pure chromium flakes, pure iron particles, and aluminum-molybdenum master alloy as raw materials and proportioning them according to the designed mass percentages of the alloy, then mixing the proportioned raw materials evenly and repeatedly melting them using a vacuum melting furnace to obtain an alloy ingot; (2)Forging and rolling deformation processing Successively heating the alloy ingot obtained in the above step (1) to the target temperature and holding it, then performing forging shaping, medium-temperature and room-temperature rolling deformation treatments, and obtaining alloy rolling sheets; (3)Annealing treatment Putting the alloy rolling sheets obtained in the above step (2) into a heat treatment furnace at a temperature of T4 and holding for a time t4, then taking them out for rapid cooling, and subsequently polishing their surfaces to finally obtain a superelastic titanium alloy material.

8. The preparation method of the low-density superelastic functional titanium alloy according to claim 7, characterized in that: In the above step (1), when preparing an alloy ingot with a weight of greater than or equal to 20 kg, a vacuum electron beam melting furnace or a vacuum consumable electrode melting furnace is selected for the vacuum melting furnace, and the number of melting times of the vacuum electron beam melting furnace is 1 - 2 times; In step (1), when preparing alloy ingots weighing less than 20 kg, a vacuum levitation melting furnace or a vacuum non-consumable melting furnace is selected as the vacuum melting furnace. The number of repeated melting times for the vacuum levitation melting furnace or the vacuum consumable melting furnace is 2 - 4 times, while the number of repeated melting times for the vacuum non-consumable melting is 5 - 8 times, and the vacuum degree is 10 -4 Pa~10 -2 Pa.

9. The preparation method of the low-density superelastic functional titanium alloy according to claim 7, characterized in that: In the above step (1), when repeatedly melting the alloy ingot, the ingot melted in the previous time needs to be inverted before starting a new melting to reduce segregation and obtain an ingot with uniform composition.

10. The preparation method of the low-density superelastic functional titanium alloy according to claim 7, characterized in that , In the above step (2), the specific processes of forging shaping, medium-temperature and room-temperature rolling deformation treatments are as follows: (2.1)Forging shaping Putting the alloy ingot obtained in the above step (1) into a heat treatment furnace at a temperature of T1 and holding for a time t1, then performing forging processing, and obtaining an alloy plate blank after surface grinding treatment; (2.2)Medium-temperature rolling Putting the alloy plate blank obtained in the above step (2.1) into a heat treatment furnace at a temperature of T2 and holding for a time t2, then performing rolling at a temperature of T2, surface treatment, and segmentation to obtain alloy primary plates; (2.3)Room-temperature rolling Putting the alloy primary plates obtained in the above step (2.2) into a heat treatment furnace at a temperature of T3 and holding for a time t3, cooling and then performing room-temperature rolling treatment to obtain alloy rolling sheets.

11. The preparation method of the low-density superelastic functional titanium alloy according to claim 10, characterized in that: The temperature T in the forging shaping in the above step (2.1) 1 is 1050 °C - 1200 °C, the time t1 is 4 h - 8 h, and the total deformation amount is greater than or equal to 120%.

12. The preparation method of the low-density superelastic functional titanium alloy according to claim 10, wherein: The temperature T2 in the medium-temperature rolling in the above step (2.2) is 720 °C - 850 °C, the time t2 is 2 h - 4 h, and the total deformation amount is greater than or equal to 50%.

13. The preparation method of the low-density superelastic functional titanium alloy according to claim 7, characterized in that: The temperature T3 in the room-temperature rolling in step (2.3) is 580 °C to 660 °C, the time t3 is 0.2 h to 1 h. When the room-temperature rolling deformation amount is greater than 20%, the heat treatment at temperature T3 is repeated, and the total deformation amount is greater than or equal to 60%.

14. The preparation method of the low-density superelastic functional titanium alloy according to claim 7, characterized in that: The temperature T4 in the annealing treatment in step (3) is 680 °C to 900 °C, and the time t4 is 0.5 h to 4 h.

15. The preparation method of the low-density superelastic functional titanium alloy according to claim 7, characterized in that, The mass percentages of the alloy ingot obtained in step (1) are as follows: Al: 4.2 to 5.0%, Cr: 1.6 to 2.2%, Fe: 0.8 to 1.2%, Mo: 3.0 to 4.2%, and the balance is Ti and inevitable impurity elements.

Images