Method for improving superelasticity of beta titanium alloy by preparing submicron grains

Abstract

The invention discloses a method for improving the superelasticity of beta titanium alloy by preparing submicron grains, which comprises the following steps: firstly, obtaining a beta titanium alloy cast ingot by a vacuum argon arc melting method, and carrying out homogenization solution treatment on the beta titanium alloy cast ingot to ensure that a single beta phase structure is obtained; the method comprises the following steps: firstly, treating a beta titanium alloy ingot, then, carrying out large-deformation cold rolling treatment on the treated beta titanium alloy ingot with the cold rolling deformation being greater than 94%, and finally, carrying out low-temperature short-time solution treatment on the alloy plate subjected to large-deformation cold rolling treatment with the solution treatment temperature being 50-100 DEG C higher than the beta transformation temperature for 150-200s, so as to obtain the beta titanium alloy with submicron grains. According to the beta titanium alloy subjected to large-deformation cold rolling and low-temperature short-time solution treatment, the grain size reaches the submicron level, the minimum grain size is 0.3 micron, and the total recovery strain reaches up to 4.85%; according to the method, beta titanium alloy grains are refined to the submicron level through large-deformation cold rolling and low-temperature short-time solution treatment, so that the hyperelasticity of the beta titanium alloy grains is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy, and in particular relates to a method for improving the superelasticity of beta titanium alloy by preparing submicron grains. Technical Background

[0002] β-titanium alloy has good biocompatibility and is the main load-bearing biological implant material. It is often used in dentistry, hip joints, stents, joints, bone plates, intramedullary nails, spine, etc. For β-titanium alloy, when external stress is applied, α" (martensite) phase transformation can occur above the martensite transformation temperature. When the external stress is eliminated, the shape of the α" reverse phase transformation returns to its original state. This phenomenon is called superelasticity. Superelasticity is widely used. On the one hand, it can play a buffering role when used as a human implant. On the other hand, superelasticity can also be used for orthodontic treatment of teeth. Ti-Ni-based alloys have good superelasticity, but because Ni + It is easy to cause allergic reactions, so it is urgent to develop a nickel-free β-titanium alloy. At present, the developed Ti-Nb-based alloys have low yield strength, and twins and dislocation slips are easy to open. These crystal defects hinder the α" phase transformation and its reverse transformation, resulting in superelasticity weakening. Improving the superelasticity of β-titanium alloys is an urgent problem to be solved.

[0003] Grain refinement strengthening is a strengthening method that can achieve a simultaneous improvement in strength and superelasticity. Too large a grain size will lead to uneven stress distribution in the grains, making it easier for dislocations to slip, reducing the strength of the material and weakening its superelasticity. Grain refinement can hinder dislocation movement, making it difficult for dislocations to slip, and increasing the difficulty of plastic deformation of the material. At the same time, grain refinement also reduces the size of α", which is beneficial to the α" phase transformation and its reverse transformation, significantly improving the superelasticity of β titanium alloys. Therefore, how to improve the superelasticity of β titanium alloys by grain refinement is a problem that needs to be solved at present. Summary of the invention

[0004] In order to solve the above technical problems, the object of the present invention is to provide a method for improving the superelasticity of β titanium alloy by preparing submicron grains.

[0005] The technical solution adopted by the present invention is:

[0006] A method for improving the superelasticity of β titanium alloy by preparing submicron grains, specifically comprising the following steps:

[0007] Step 1, obtaining a β-titanium alloy ingot by a vacuum argon arc melting method, and performing a homogenization solid solution treatment on the obtained β-titanium alloy ingot to ensure that a single β-phase structure is obtained, which is convenient for subsequent large deformation cold rolling treatment;

[0008] Step 2, performing large deformation cold rolling on the alloy ingot processed in step 1 to form fine grains to obtain an alloy plate;

[0009] Step 3: performing a low-temperature short-time solution treatment on the alloy plate to control the growth of rolled grains to obtain a β-titanium alloy with submicron grains.

[0010] Furthermore, in step 1, the alloy elements are vacuum argon arc melted according to the proportions. To ensure uniform alloy composition, the β-titanium alloy ingot is turned over and remelted to obtain a β-titanium alloy ingot with uniform composition.

[0011] Furthermore, the homogenization solution treatment in step 1 is carried out at a vacuum degree of less than 4×10 -3 Pa, heat treated at 950-1050℃, which is much higher than the β phase transition temperature, for 2h, and then water-cooled to room temperature.

[0012] Furthermore, the large deformation rolling and cold rolling in step 2 is carried out by multiple rolling passes at room temperature, and the deformation amount is greater than 94%.

[0013] Furthermore, the low-temperature short-time solution treatment in step 3 is performed under argon protection at a temperature 50 to 100° C. higher than the β phase transformation temperature for 150 to 200 seconds, and then water-cooled to room temperature.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] This design scheme ensures that a single β phase structure is obtained by subjecting the ingot to a homogenized solution treatment at 950-1050℃, which is much higher than the β transformation temperature, after smelting, to facilitate the subsequent large deformation cold rolling treatment. After that, large deformation rolling is carried out to introduce a large number of dislocations and large deformation energy storage in the alloy plate, providing a driving force for recrystallization for the subsequent low-temperature short-time solution treatment and forming fine grains. The temperature of the low-temperature short-time solution treatment is designed to be 50-100℃ higher than the β transformation temperature to control the growth of the rolled grains, and finally obtain submicron grains to significantly improve the superelasticity of the β titanium alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The phase diagram of the β titanium alloy obtained by the method for improving the superelasticity of the β titanium alloy by preparing submicron grains in Example 1 of the present invention;

[0017] Figure 2 This is a microscopic morphology of a β titanium alloy obtained by preparing submicron grains to improve the superelasticity of a β titanium alloy according to Example 1 of the present invention;

[0018] Figure 3 is a grain size diagram of the β titanium alloy obtained by the method for improving the superelasticity of the β titanium alloy by preparing submicron grains in Example 1 of the present invention;

[0019] Figure 4The cyclic tensile curve of the β titanium alloy obtained by the method for improving the superelasticity of the β titanium alloy by preparing submicron grains in Example 1 of the present invention;

[0020] Figure 5 This is a microscopic morphology of the alloy after deformation of the β-titanium alloy of Comparative Example 1 of the present invention;

[0021] Figure 6 is a grain size diagram of the β titanium alloy of Comparative Example 1 of the present invention;

[0022] Figure 7 It is the cyclic tensile curve of the β titanium alloy of comparative example 1 of the present invention. DETAILED DESCRIPTION

[0023] The following is a detailed description through specific embodiments in conjunction with the accompanying drawings.

[0024] A method for improving the superelasticity of β titanium alloy by preparing submicron grains, specifically comprising the following steps:

[0025] Step 1, obtaining a β-titanium alloy ingot by a vacuum argon arc melting method, and subjecting the obtained β-titanium alloy ingot to a homogenization solution treatment at 950-1050° C. to ensure that a single β-phase structure is obtained, so as to facilitate subsequent large deformation cold rolling treatment;

[0026] Step 2, performing large deformation cold rolling on the β-titanium alloy ingot processed in step 1 to form fine grains to obtain an alloy plate;

[0027] Step 3: Under argon protection, the alloy plate is subjected to a short-time solution treatment at a temperature 50 to 100° C. higher than the phase transition temperature, the solution treatment time is 150 to 200 seconds, and then water-cooled to room temperature to obtain a β-titanium alloy with submicron grains.

[0028] Step 4: Perform a cyclic loading tensile test with an interval of 1% on the sample after solution treatment.

[0029] Example 1

[0030] The β titanium alloy used is a TiZrNbSn alloy, and the alloy composition consists of the following components in atomic percentage: 30% Zr, 10% Nb, 1% Sn, and the balance is Ti and inevitable impurities.

[0031] Step 1: Select raw materials according to the composition, and perform vacuum argon arc melting on Ti, Zr, Nb and Sn according to the proportion. To ensure the uniform composition of the TiZrNbSn alloy ingot, turn the TiZrNbSn alloy ingot over and remelt it for 7 times to obtain a TiZrNbSn alloy ingot with uniform composition. -3Pa, a homogenization solution treatment is carried out for 2 hours at 980-1020℃, which is much higher than the β phase region of the TiZrNbSn alloy ingot, to ensure that a single β phase structure is obtained, which is convenient for large deformation cold rolling treatment.

[0032] Step 2, cold rolling the TiZrNbSn alloy ingot processed in step 1 into a plate, wherein the cold rolling process is a multi-pass rolling at room temperature until the deformation amount is 96%.

[0033] Step 3, such as Figure 1 As shown in the phase diagram, the β transition temperature (T βtrans ) is 530-550°C, which is 50-100°C higher than the β transformation temperature. Therefore, the alloy sheet obtained in step 2 is subjected to a 580-620°C solid solution treatment under argon protection, kept warm for 180s, and then water-cooled to room temperature, and finally a submicron β titanium alloy is obtained. After the low-temperature short-time solid solution treatment, Figure 2 As shown, submicron-sized grains are formed. Figure 3 For the statistical grain size diagram, the average grain size of the alloy is 0.6μm and the minimum grain size is 0.3μm.

[0034] Step 4, performing a cyclic loading tensile test with an interval of 1% on the β titanium alloy sample after the solution treatment in step 3. Figure 4 The cyclic tensile curve of the alloy has a yield strength of 350 MPa. As the strain increases, when the strain is 5%, the total recovery strain (ε r ) is 4.85% at most. From the above performance indicators, it can be seen that the superelasticity is significantly improved by refining the β titanium alloy grains to submicron level through large deformation rolling and low temperature short time solution treatment.

[0035] Comparative Example 1

[0036] The β titanium alloy used is TiZrNbSn alloy, and the alloy composition is consistent with the alloy composition of Example 1.

[0037] Step 1: Select raw materials according to the composition, and perform vacuum argon arc melting on Ti, Zr, Nb and Sn according to the composition. To ensure the uniformity of the alloy composition, turn the ingot over and remelt it. Melt it 7 times to obtain a β-titanium alloy ingot with uniform composition. -3 Pa, a homogenization solution treatment is carried out for 2 hours at 980-1020℃, which is much higher than the β phase region of the alloy, to ensure that a single β phase structure is obtained, which is convenient for large deformation cold rolling treatment.

[0038] Step 2, cold rolling the β-titanium alloy ingot processed in step 1 into a plate, wherein the cold rolling process is a multi-pass rolling at room temperature until the deformation amount is 96%.

[0039] Step 3, subjecting the β-titanium alloy sheet obtained in step 2 to a solution treatment at 880-920°C under argon protection, keeping the temperature for 180 seconds, and then cooling to room temperature with water. Figure 5 As shown, the alloy formed larger grains. Figure 6 For the statistical grain size diagram, the average grain size of β titanium alloy is 26μm and the minimum grain size is 10μm.

[0040] Step 4, performing a cyclic loading tensile test with an interval of 1% on the sample after the solution treatment in step 3. Figure 7 The cyclic tensile curve of β titanium alloy, the yield strength of the alloy is 195MPa, indicating that the increase of grain size reduces the resistance to plastic deformation. When the strain reaches 5%, the total recovery strain (ε r ) is only 2.3%. It can be seen that a larger grain size will reduce the superelasticity of β titanium alloy.

[0041] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for improving the superelasticity of β titanium alloy by preparing submicron grains, characterized in that: The specific steps include: Step 1, obtaining a β-titanium alloy ingot by a vacuum argon arc melting method, and performing a homogenization solid solution treatment on the obtained β-titanium alloy ingot to ensure that a single β-phase structure is obtained, which is convenient for subsequent large deformation cold rolling treatment; Step 2, performing large deformation cold rolling on the β-titanium alloy ingot processed in step 1 to form fine grains, thereby obtaining an alloy plate; Step 3: performing a low-temperature short-time solution treatment on the alloy plate to control the growth of rolled grains to obtain a β-titanium alloy with submicron grains.

2. The method for improving superelasticity of β titanium alloy by preparing submicron grains according to claim 1, characterized in that: In step 1, the alloy elements are vacuum argon arc melted according to the proportions. To ensure uniform alloy composition, the β-titanium alloy ingot is turned over and re-melted to obtain a β-titanium alloy ingot with uniform composition.

3. The method for improving superelasticity of β titanium alloy by preparing submicron grains according to claim 1, characterized in that: In step 1, the homogenization solution treatment is carried out in a vacuum degree of less than 4×10 -3 Pa, heat treatment at 950-1050℃ for 2h, and then water-cooling to room temperature.

4. The method for improving superelasticity of β titanium alloy by preparing submicron grains according to claim 1, characterized in that: The cold rolling process in step 2 is a multi-pass rolling at room temperature until the deformation is greater than 94%.

5. The method for improving superelasticity of β titanium alloy by preparing submicron grains according to claim 1, characterized in that: The low-temperature short-time solution treatment in step 3 is carried out under argon protection, the solution treatment temperature is 50-100° C. higher than the β phase transformation temperature, the solution treatment time is 150-200 seconds, and then water-cooled to room temperature.

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