A method for improving the superelasticity of β-type titanium alloys and its application

Abstract

This invention provides a method for improving the superelasticity of β-type titanium alloys and its application. The method includes: pre-deformation treatment of a β-type titanium alloy billet, including multi-pass cold deformation of the billet, wherein the deformation per pass is less than or equal to 5%, and no intermediate annealing is performed between passes, to obtain a β-type titanium alloy material with a total deformation reaching a preset deformation amount; solution treatment of the β-type titanium alloy material, including heating and holding the material at that temperature followed by cooling; and aging treatment of the solution-treated β-type titanium alloy material, including heating it to 100-150°C, holding it at that temperature, and then cooling. This method can improve the superelasticity and plasticity of β-type low-modulus titanium alloys, overcoming the brittleness of existing β-type titanium alloy materials. Based on the excellent superelasticity, strength, and plasticity of this β-type titanium alloy, it can meet the requirements for flexible devices under high strain conditions in implantable medical devices.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy material processing technology, specifically relating to a method for improving the superelasticity of β-type titanium alloys and its application. Background Technology

[0002] Metastable β-titanium alloys have low modulus, good biocompatibility, and shape memory effect, and can be used in medical implantable devices such as catheters, orthodontic wires, cardiovascular stents, and guidewires, showing good application prospects.

[0003] The superelasticity of metastable β-titanium alloys is mainly attributed to the reversible martensitic phase transformation between the austenitic parent phase β and stress-induced martensite α” during mechanical stress loading and unloading. Room-temperature superelasticity has been reported in Ti-Nb, Ti-Nb-Zr, Ti-Nb-Ta-Zr, and Ti-Mo materials. However, most superelastic β-titanium alloys exhibit low critical stresses for superelastic deformation due to their low phase transformation strain, which is detrimental to the stability of superelastic deformation. Current methods for increasing the critical stress for superelastic deformation mainly fall into four categories: solution treatment, grain refinement, work hardening, and precipitation strengthening. However, the low plasticity and high springback of β-titanium alloys make their processing and preparation difficult. Furthermore, current precipitation strengthening heat treatments generally use a temperature range of 200-400˚C. Within this range, ω-phase precipitation is a spontaneous process. Higher temperatures and longer aging times increase excessive ω-phase precipitation, leading to the enrichment of the stable ω-phase in the β matrix, thus causing embrittlement of the β-Ti alloy. Summary of the Invention

[0004] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions:

[0005] One objective of this invention is to provide a method for improving the superelasticity of β-type titanium alloys, the method comprising:

[0006] A pre-deformation treatment is performed on a β-type titanium alloy billet. The pre-deformation treatment includes performing multi-pass cold deformation on the β-type titanium alloy billet. The deformation amount of each pass in the multi-pass cold deformation is less than or equal to 5%, and no intermediate annealing treatment is performed between passes, so as to obtain a β-type titanium alloy material with a total deformation amount reaching the preset deformation amount.

[0007] The β-type titanium alloy material is subjected to a solution treatment, which includes heating and holding the β-type titanium alloy material at a certain temperature followed by a first cooling.

[0008] The β-type titanium alloy material that has undergone the solution treatment is subjected to aging treatment, which includes heating it to 100-150°C and holding it at that temperature before a second cooling.

[0009] The multi-pass cold deformation described in this invention refers to the multi-pass deformation of β-type titanium alloy billets at a temperature of 15~25℃.

[0010] The preparation method provided by this invention involves multi-pass cold deformation of β-type titanium alloy billets without intermediate annealing between passes, thus avoiding the precipitation and growth of the ω-phase. Simultaneously, aging treatment at a relatively low temperature (100-150℃) ensures uniform and controllable precipitation of the ω-phase, resulting in a β-type titanium alloy material with excellent superelasticity and plasticity. Furthermore, this method requires lower energy consumption due to the reduced aging temperature. If the deformation per pass is too large (greater than 5%), excessive hardening and decreased plasticity will occur, necessitating intermediate annealing to eliminate hardening before continuing cold deformation. Intermediate annealing eliminates most defects generated during the deformation history, reducing the promoting effect of cold deformation on the solid solution process and inhibiting grain growth. On the other hand, a large deformation amount and intermediate annealing may cause premature precipitation and growth of the ω-phase in localized areas, hindering the control of the precipitate size and distribution. However, within the appropriate deformation range provided by this invention, uniform hardening of the microstructure can be guaranteed, thereby promoting uniform precipitation of the ω-phase during aging.

[0011] In some preferred embodiments, the deformation amount per pass of the multi-pass cold deformation is 3-5%.

[0012] In some embodiments, the multi-pass cold deformation results in a total deformation of the β-type titanium alloy material of more than 50%, preferably more than 70%.

[0013] In some embodiments, the solution treatment specifically includes: heating the β-type titanium alloy material to 630-700°C, holding it at that temperature, and then cooling it.

[0014] In some embodiments, the heat treatment time is 20-30 minutes.

[0015] In some embodiments, the solution treatment is performed at a heating rate of 15-20°C / min. For example, the temperature is raised to 630-700°C at a heating rate of 15-20°C / min and held for 20-30 minutes before cooling.

[0016] In some embodiments, the solution treatment is performed under an inert atmosphere or vacuum conditions.

[0017] In some embodiments, the heat preservation time for the aging treatment is 12~48h.

[0018] In some embodiments, the aging treatment is performed at a heating rate of 3-5°C / min. For example, the temperature is raised to 100-150°C at a rate of 3-5°C / min and held for 12-48 hours before cooling.

[0019] In some embodiments, the aging process is performed under inert atmosphere, air, or vacuum conditions.

[0020] In some embodiments, the first cooling method includes water cooling.

[0021] In some embodiments, the second cooling method includes water cooling and / or air cooling.

[0022] In some embodiments, the β-type titanium alloy material is a metastable β-titanium alloy.

[0023] In some embodiments, the β-type titanium alloy material includes Ti, Nb, Ta, and Zr elements, or includes Ti, Nb, and Zr elements.

[0024] In some embodiments, the β-type titanium alloy material comprises 22-36% Nb, 6-16% Ta, and 3-7% Zr, with the remainder comprising Ti.

[0025] In some embodiments, the β-type titanium alloy blank includes a β-type titanium alloy bar blank, and the β-type titanium alloy material obtained by the pre-deformation treatment is a bar, wire, filament, or sheet / strip.

[0026] A second objective of this invention is to provide a β-type titanium alloy, which is obtained by processing the method described in any one of the present invention.

[0027] In some embodiments, the recoverable strain of the β-type titanium alloy at room temperature is 1.7% or more; the stress required for the first loading to induce martensitic phase transformation of the β-type titanium alloy is 155 MPa or more; and the maximum stress of the β-type titanium alloy under 4.5% strain is 507 MPa or more.

[0028] A third objective of this invention is to provide the use of the aforementioned β-type titanium alloy in the manufacture of medical devices.

[0029] In some embodiments, the medical device includes an implantable medical device.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] (1) The method provided by the present invention improves the strength of β titanium alloy by multi-pass cold deformation and pre-deformation treatment with a deformation amount of less than or equal to 5% per pass, and there is no intermediate annealing between the passes to avoid the precipitation and growth of ω phase; at the same time, low temperature aging treatment is combined to achieve uniform and controllable precipitation of ω phase, thereby obtaining β titanium alloy material with good superelasticity and good plasticity, solving the disadvantage of the titanium alloy material obtained by the prior art being relatively brittle;

[0032] (2) The recoverable strain of the titanium alloy material provided by the present invention is more than 1.7% at room temperature, and more than 2.2% in some preferred embodiments; the stress required for the first loading to induce martensitic phase transformation is more than 155 MPa, and more than 280 MPa in some preferred embodiments; and its maximum stress under 4.5% strain conditions can reach more than 507 MPa, and more than 510 MPa in some preferred embodiments; the excellent superelasticity, strength and plasticity of the titanium alloy material can well meet the requirements for the use of flexible devices under large strain conditions of implantable medical devices;

[0033] (3) The aging treatment temperature (100-150℃) used in the method provided by the present invention is lower than the aging treatment temperature (200-400℃) of the prior art, which can reduce processing energy consumption and help improve energy saving and efficiency in alloy manufacturing engineering. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application 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 recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 These are the hyperelastic performance curves of the titanium alloy materials prepared in Examples 2, 3 and Comparative Example 1 of the present invention. The horizontal axis Strain represents strain (%) and the vertical axis Stress represents stress (MPa).

[0036] Figure 2 These are the curves showing the changes in recoverable strain and applied strain of titanium alloy materials prepared under different aging time conditions at 100℃ in Examples 1-4 and Comparative Example 1 of the present invention.

[0037] Figure 3a These are metallographic images of the titanium alloy material prepared in Example 3 of this invention;

[0038] Figure 3b These are TEM images of the nano-precipitated phases of the titanium alloy material prepared in Example 3 of this invention;

[0039] Figure 4 The XRD spectra of titanium alloy materials prepared under different aging time conditions at 100℃ in Examples 1-3 of this invention are shown. Detailed Implementation

[0040] The technical solutions of the present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention. The specific functional details disclosed herein should not be construed as limiting, but are merely intended to form the basis of the claims and to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0041] In addition, unless otherwise specified, all raw materials used in the following embodiments can be purchased from the market or other sources, and all production and testing equipment used are known in the art.

[0042] Example 1

[0043] This embodiment provides a method for improving the superelasticity of β-titanium alloys through low-temperature heat treatment, specifically including the following steps:

[0044] (1) A β titanium alloy bar with a diameter of 3.5 mm (the material is Ti-29Nb-11Ta-5Zr (TNTZ) alloy) was cold-drawn in multiple passes. The cold drawing deformation rate of each pass was 5%. There was no intermediate annealing during the cold drawing process. The cold drawing yielded a β titanium alloy wire with a diameter of 1 mm. Its metallographic structure was a single-phase equiaxed grain structure with no obvious precipitates.

[0045] (2) The β titanium alloy wire obtained above is subjected to solid solution treatment, specifically including: heating to 700°C at a heating rate of 20°C / min under argon protective atmosphere, holding at 700°C for 30min, and then water cooling. Its metallographic structure consists of single-phase equiaxed grains β and part of martensite α”.

[0046] (3) The β titanium alloy wire that has undergone the above solution treatment is subjected to aging treatment, specifically including: heating to 100°C at a heating rate of 5°C / min under argon protective atmosphere, holding at 100°C for 12 h, and then water cooling to obtain superelastic titanium alloy wire, whose structure consists of single-phase equiaxed grains β and nano-precipitated phase ω.

[0047] The diameter of the superelastic titanium alloy wire obtained in this embodiment is 0.9 mm. This titanium alloy wire has superelastic properties. The tensile test method (GB / T 228.1-2010) shows that its room temperature recoverable strain is 1.7%, the stress required to induce martensite under the first loading is 155 MPa, and the maximum stress at 4.5% strain is 507 MPa.

[0048] Example 2

[0049] This embodiment provides a method for improving the superelasticity of β-titanium alloys through low-temperature heat treatment, specifically including the following steps:

[0050] (1) A β titanium alloy bar with a diameter of 3.5 mm (the material is Ti-29Nb-11Ta-5Zr (TNTZ) alloy) was cold-drawn in multiple passes. The cold drawing deformation rate of each pass was 3.5%. There was no intermediate annealing during the cold drawing process. The cold drawing yielded a β titanium alloy wire with a diameter of 1 mm. Its metallographic structure was a single-phase equiaxed grain structure with no obvious precipitates.

[0051] (2) The β titanium alloy wire obtained above is subjected to solid solution treatment, specifically including: heating to 700°C at a heating rate of 15°C / min under argon protective atmosphere, holding at 700°C for 30min, and then water cooling. Its metallographic structure consists of single-phase equiaxed grains β and part of martensite α”.

[0052] (3) The β-titanium alloy wire that has undergone the above solution treatment is subjected to aging treatment, specifically including: aging at 5°C under an argon protective atmosphere. o Heating was carried out at a rate of C / min to 100℃, held at 100℃ for 24 h, and then water-cooled to obtain a superelastic titanium alloy wire. Its metallographic structure consists of single-phase equiaxed grains β and nano-precipitated phase ω.

[0053] The diameter of the superelastic titanium alloy wire obtained in this embodiment is 1.1 mm. This titanium alloy wire has superelastic properties. It was tested using the same method as in Example 1. The room temperature recoverable strain is 1.8%, the stress required to induce martensite under the first loading is 220 MPa, and the maximum stress at 4.5% strain is 511 MPa.

[0054] Example 3

[0055] This embodiment provides a method for improving the superelasticity of β-titanium alloys through low-temperature heat treatment, specifically including the following steps:

[0056] (1) A β titanium alloy bar with a diameter of 3.5 mm (the material is Ti-29Nb-11Ta-5Zr (TNTZ) alloy) was cold-drawn in multiple passes. The cold drawing deformation rate of each pass was 3%. There was no intermediate annealing during the cold drawing process. The β titanium alloy wire with a diameter of 1 mm obtained by cold drawing had a single-phase equiaxed grain structure and no obvious precipitates.

[0057] (2) The β-titanium alloy wire obtained above is subjected to solution treatment, specifically including: under an argon protective atmosphere, at 18 o The temperature was increased to 700℃ at a heating rate of C / min, held at 700℃ for 30 min, and then water-cooled. Its metallographic structure consists of single-phase equiaxed grains β and part of martensite α”.

[0058] (3) The β-titanium alloy wire that has undergone the above solution treatment is subjected to aging treatment, specifically including: aging at 3°C ​​under an argon protective atmosphere. oHeating was carried out at a rate of C / min to 100℃, held at 100℃ for 48 h, and then water-cooled to obtain a superelastic titanium alloy wire, whose microstructure consists of single-phase equiaxed grains β and nano-precipitated phase ω.

[0059] The diameter of the superelastic titanium alloy wire obtained in this embodiment is 1 mm. This titanium alloy wire has superelastic properties. It was tested using the same method as in Example 1. The room temperature recoverable strain is 2.3%, the stress required to induce martensite under the first loading is 280 MPa, and the maximum stress at 4.5% strain is 514 MPa.

[0060] Figure 3a This is a metallographic photograph of the β-titanium alloy wire prepared in this embodiment. Figure 3b This is a TEM image of nanoprecipitated phases. (Source: [Insert Source Here]) Figure 3a and Figure 3b It can be seen that the microstructure of the β titanium alloy wire prepared in this embodiment consists of equiaxed β grains with a grain size of about 10 μm and nano-precipitated ω phase within the grains.

[0061] Figure 4 The XRD spectra of titanium alloy materials prepared under different aging time conditions at 100℃ in Examples 1-3 of this invention are shown.

[0062] Example 4

[0063] This embodiment provides a method for improving the superelasticity of β-titanium alloys through low-temperature heat treatment, specifically including the following steps:

[0064] (1) A β titanium alloy bar with a diameter of 3.5 mm (the material is Ti-29Nb-11Ta-5Zr (TNTZ) alloy) was cold-drawn in multiple passes. The cold drawing deformation rate of each pass was 3%. There was no intermediate annealing during the cold drawing process. The β titanium alloy wire with a diameter of 1 mm obtained by cold drawing had a single-phase equiaxed grain structure and no obvious precipitates.

[0065] (2) The β-titanium alloy wire obtained above is subjected to solution treatment, specifically including: under an argon protective atmosphere, at 20 o The temperature was increased to 700℃ at a heating rate of C / min, held at 700℃ for 30 min, and then water-cooled. Its metallographic structure consists of single-phase equiaxed grains β and part of martensite α”.

[0066] (3) The β-titanium alloy wire that has undergone the above solution treatment is subjected to aging treatment, specifically including: aging at 5°C under an argon protective atmosphere. o Heating was carried out at a rate of C / min to 100℃, held at 100℃ for 36 h, and then water-cooled to obtain a superelastic titanium alloy wire. Its metallographic structure consists of single-phase equiaxed grains β and nano-precipitated phase ω.

[0067] The diameter of the superelastic titanium alloy wire obtained in this embodiment is 1.05 mm. This titanium alloy wire has superelastic properties. It was tested using the same method as in Example 1. The room temperature recoverable strain is 2.08%, the stress required to induce martensite under the first loading is 251 MPa, and the maximum stress at 4.5% strain is 522 MPa.

[0068] Example 5

[0069] This embodiment provides a method for preparing β-titanium alloy with improved superelasticity through low-temperature heat treatment, specifically including the following steps:

[0070] (1) A β titanium alloy bar with a diameter of 3.5 mm (the material is Ti-29Nb-11Ta-5Zr (TNTZ) alloy) is cold-drawn in multiple passes. The cold drawing deformation rate of each pass is 3.5%. There is no intermediate annealing during the cold drawing process. A β titanium alloy wire with a diameter of 1 mm is obtained by cold drawing.

[0071] (2) The β-titanium alloy wire obtained above is subjected to solution treatment, specifically including: under an argon protective atmosphere, at 15 o The temperature was increased to 630℃ at a heating rate of C / min, held at 630℃ for 20 min, and then water-cooled.

[0072] (3) The β-titanium alloy wire that has undergone the above solution treatment is subjected to aging treatment, specifically including: aging at 3°C ​​under an argon protective atmosphere. o Heating was carried out at a rate of C / min to 100℃, held at 100℃ for 48 h, and then water-cooled to obtain superelastic titanium alloy wire.

[0073] The diameter of the superelastic titanium alloy wire obtained in this embodiment is 1 mm. This titanium alloy wire has superelastic properties and was tested using the same method as in Example 1. Its room temperature recoverable strain is 1.9%, the stress required to induce martensite under the first loading is 210 MPa, and the maximum stress at 4.5% strain is 510 MPa.

[0074] Example 6

[0075] The only difference between Example 6 and Example 3 is that the solution treatment temperature in Example 6 is 660°C. The rest of the process is the same as in Example 1, and will not be repeated here.

[0076] The same method as in Example 3 was used for testing, and the room temperature recoverable strain was measured to be 1.97%, the stress required for the first loading to induce martensite was 235 MPa, and the maximum stress at 4.5% strain was 512 MPa.

[0077] Example 7

[0078] The only difference between Example 7 and Example 3 is that the aging treatment temperature in Example 7 is 150°C. The rest of the implementation is the same as in Example 3, and will not be repeated here.

[0079] The same method as in Example 3 was used for testing, and the room temperature recoverable strain was measured to be 2.08%, the stress required for the first loading to induce martensite was 233 MPa, and the maximum stress at 4.5% strain was 518 MPa.

[0080] Example 8

[0081] The only difference between Example 8 and Example 3 is that the aging treatment temperature in Example 8 is 125°C. The rest of the implementation is the same as in Example 3, and will not be repeated here.

[0082] The same method as in Example 3 was used for testing, and the room temperature recoverable strain was measured to be 2.06%, the stress required for the first loading to induce martensite was 208 MPa, and the maximum stress at 4.5% strain was 517 MPa.

[0083] Comparative Example 1

[0084] The preparation method of the titanium alloy in Comparative Example 1 specifically includes the following steps:

[0085] (1) A β titanium alloy bar with a diameter of 3.5 mm (the material is Ti-29Nb-11Ta-5Zr (TNTZ) alloy) is cold-drawn in multiple passes. The cold drawing deformation rate of each pass is 3%. There is no intermediate annealing during the cold drawing process. The β titanium alloy wire with a diameter of 1 mm is obtained by cold drawing.

[0086] (2) The β-titanium alloy wire obtained above is subjected to solution treatment, specifically including: under an argon protective atmosphere, at 18 o The temperature was increased to 700℃ at a heating rate of C / min, held at 700℃ for 30 min, and then water-cooled.

[0087] The titanium alloy wire obtained in this comparative example has a diameter of 1 mm. It was tested using the same method as in Example 1. The room temperature recoverable strain was 1.1%, the stress required for the first loading to induce martensite was 120 MPa, and the maximum stress at 4.5% strain was 491 MPa.

[0088] Figure 1 These are the hyperelastic property curves of the titanium alloy materials prepared in Examples 2 (700W / O + Aged at 100℃ for 24h), 3 (700W / O + Aged at 100℃ for 48h), and Comparative Example 1 (700W / O) of the present invention. The horizontal axis represents strain (%), and the vertical axis represents stress (MPa). According to... Figure 1It can be seen that, compared with Comparative Example 1, the hyperelasticity of the titanium alloy materials in Examples 2 and 3 is significantly better than that in Comparative Example 1.

[0089] Figure 2 These are the curves showing the change in recoverable strain versus applied strain of titanium alloy materials prepared under different aging time conditions at 100℃ in Examples 1-4 and Comparative Example 1 of this invention. According to... Figure 2 It can be seen that, compared with Comparative Example 1, the recoverable strain of Examples 1-4 is significantly higher than that of Comparative Example 1.

[0090] Comparative Example 2

[0091] The preparation method of the titanium alloy in Comparative Example 2 specifically includes the following steps:

[0092] (1) A β titanium alloy bar with a diameter of 3.5 mm (the material is Ti-29Nb-11Ta-5Zr (TNTZ) alloy) is cold-drawn in multiple passes. The cold drawing deformation rate of each pass is 3.5%. There is no intermediate annealing during the cold drawing process. The β titanium alloy wire with a diameter of 1 mm is obtained by cold drawing.

[0093] (2) The β-titanium alloy wire obtained above is subjected to solution treatment, specifically including: under an argon protective atmosphere, at 15 o The temperature was increased to 630℃ at a heating rate of C / min, held at 630℃ for 20 min, and then water-cooled.

[0094] The titanium alloy wire obtained in this comparative example has a diameter of 1 mm. It was tested using the same method as in Example 1. The room temperature recoverable strain was 1.0%, the stress required for the first loading to induce martensite was 150 MPa, and the maximum stress at 4.5% strain was 501 MPa.

[0095] Comparative Example 3

[0096] The only difference between Comparative Example 3 and Example 3 is that Comparative Example 3 performs intermediate annealing between multiple cold drawing deformations. The specific method of Comparative Example 3 is as follows:

[0097] A β-titanium alloy bar with a diameter of 3.5 mm (material is Ti-29Nb-11Ta-5Zr (TNTZ) alloy) was cold-drawn in 4 passes, with cold deformation rates of 40%, 30%, 24% and 10% for each pass, and intermediate annealing was carried out between the deformation passes. The intermediate annealing treatment was carried out by holding at 600℃ for 30 min under argon protective atmosphere and then furnace cooling.

[0098] After cold drawing, the filaments underwent the same solution treatment and aging treatment as in Example 3, ultimately yielding filaments with a diameter of 1 mm.

[0099] The same method as in Example 1 was used for testing. The room temperature recoverable strain was 1.67%, the stress required for the first loading to induce martensite was 127 MPa, and the maximum stress at 4.5% strain was 452 MPa.

[0100] Comparing Example 3 and Comparative Example 3, it can be seen that a higher variable amount and intermediate annealing treatment will lead to a reduction in the effective deformation that promotes phase transformation, less martensite α” after solution treatment, and ultimately a lower martensitic phase transformation conversion rate and weaker superelasticity during the superelastic process.

[0101] Comparative Example 4

[0102] The only difference between Comparative Example 4 and Example 3 is that the aging treatment in Comparative Example 4 is carried out under an argon protective atmosphere at 15°C. o The temperature was increased to 550°C at a heating rate of C / min, held at 550°C for 1 hour, and then water-cooled to obtain a filament with a diameter of 1 mm. The rest of the procedure was the same as in Example 3 and will not be repeated here.

[0103] The same method as in Example 1 was used for testing. The room temperature recoverable strain was 2.01%, the stress required for the first loading to induce martensite was 113 MPa, and the maximum stress at 4.5% strain was 452 MPa.

[0104] Comparing Example 1 and Comparative Example 4, it can be seen that the stabilizing effect of the ω phase relative to the β phase obtained by high-temperature aging is weaker than that obtained by low-temperature aging. The room-temperature recoverable strain and the stress required to induce martensite are both less than those obtained by low-temperature aging.

[0105] In summary, to improve the superelasticity, especially the critical stress, of β-titanium alloys, this invention employs a multi-pass cold deformation process on the basis of low elastic recovery and good plasticity to avoid excessive plastic strain that could lead to material failure. Simultaneously, there is no intermediate annealing between deformation passes to prevent the precipitation and growth of the ω-phase. Furthermore, low-temperature aging treatment ensures uniform and controllable precipitation of the ω-phase, thereby increasing the critical stress for superelastic deformation while preventing excessive ω-phase precipitation. This results in a β-titanium alloy material with excellent combined superelasticity, strength, and plasticity.

[0106] All aspects, embodiments, features, and examples of this invention are to be regarded as illustrative in all respects and are not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0107] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0108] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method for improving the superelasticity of β-type titanium alloys, characterized in that, include: Pre-deformation treatment of β-type titanium alloy billet includes multi-pass cold deformation of the β-type titanium alloy billet, wherein the deformation amount of each pass of the multi-pass cold deformation is less than or equal to 5%, and no intermediate annealing is performed between passes, and the total deformation amount of the β-type titanium alloy billet is greater than 50% by the multi-pass cold deformation, thereby obtaining β-type titanium alloy material. The β-type titanium alloy material is subjected to solution treatment, which includes heating and holding the β-type titanium alloy material at a certain temperature followed by a first cooling. The β-type titanium alloy material that has undergone the solution treatment is subjected to aging treatment, which includes heating it to 100-150°C and holding it at that temperature before a second cooling.

2. The method according to claim 1, characterized in that: The deformation amount per pass in the multi-pass cold deformation is 3-5%.

3. The method according to claim 1, characterized in that: The solution treatment specifically includes: heating the β-type titanium alloy material to 630-700℃ and holding it at that temperature before cooling; and / or, the holding time of the solution treatment is 20-30 min; and / or, the heating rate of the solution treatment is 15-20℃ / min; and / or, the solution treatment is carried out under an inert atmosphere or vacuum conditions.

4. The method according to claim 1, characterized in that: The holding time for the aging treatment is 12~48h; and / or the heating rate for the aging treatment is 3~5℃ / min; and / or the aging treatment is carried out under inert atmosphere, air or vacuum conditions.

5. The method according to claim 1, characterized in that: The first cooling method includes water cooling.

6. The method according to claim 1, characterized in that: The second cooling method includes water cooling and / or air cooling.

7. The method according to claim 1, characterized in that: The β-type titanium alloy material is a metastable β-titanium alloy.

8. The method according to claim 1, characterized in that: The β-type titanium alloy material includes Ti, Nb, Ta and Zr elements or includes Ti, Nb and Zr elements.

9. The method according to claim 8, characterized in that: The β-type titanium alloy material comprises 22-36 wt% Nb, 6-16 wt% Ta and 3-7 wt% Zr, with the remainder being Ti.

10. The method according to claim 1, characterized in that: The β-type titanium alloy billet includes β-type titanium alloy bar billet, and the β-type titanium alloy material obtained by the pre-deformation treatment is bar, wire, filament or sheet / strip.

11. A β-type titanium alloy, characterized in that: It is processed by the method according to any one of claims 1-10.

12. The β-type titanium alloy according to claim 11, characterized in that: The β-type titanium alloy has a recoverable strain of more than 1.7% at room temperature, a stress of more than 155 MPa required for the first loading to induce martensitic phase transformation, and a maximum stress of more than 507 MPa under a strain of 4.5%.

13. Use of a β-type titanium alloy processed by any one of claims 1-10 in the manufacture of medical devices, said medical devices including implantable medical devices.

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