Preparation method of high-density Ti-Nb alloy

Abstract

The invention belongs to the technical field of titanium alloy powder preparation, and particularly relates to a preparation method of a high-density Ti-Nb alloy. The preparation method comprises the following steps: firstly, mixing Ti powder and Nb powder, pressing, and then carrying out first vacuum sintering to obtain a Ti-Nb primarily homogenized alloy; then slicing and then carrying out hydrotreating, and carrying out ball milling to obtain hydrogenated Ti-Nb alloy powder; and finally, the hydrogenated Ti-Nb alloy powder is pressed and then subjected to second-time vacuum dehydrogenation sintering, a large number of defects are generated through dehydrogenation, element diffusion and sintering densification are facilitated, the homogenized and high-quality dense Ti-Nb alloy is finally prepared, and the bottleneck that the alloy prepared through a traditional powder metallurgy technology is large in melting point difference and low in density is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy powder preparation, and more specifically, relates to a method for preparing a high-density Ti-Nb alloy. Background Art

[0002] In the development of powder metallurgy technology, Ti-Nb alloys have attracted extensive attention due to their unique mechanical properties and biocompatibility, especially in applications in medical implants and aerospace. However, the difference in melting points between Ti and Nb makes the densification of traditional sintering methods face many challenges during the synthesis process. Specifically, the melting points of Ti and Nb are 1668°C and 2477°C, respectively, which are quite different. Due to its high melting point, Nb often fails to completely dissolve in the Ti matrix, forming undissolved Nb particles. These undissolved Nb particles not only affect the microstructure of the alloy, but also lead to inhomogeneity in mechanical properties, thus limiting its potential for practical application. In addition, undissolved Nb particles will lead to uneven phase distribution of the alloy, thereby affecting properties such as strength, ductility and corrosion resistance. Therefore, solving the melting point difference between Ti and Nb and the resulting densification difficulties is the key to achieving the performance optimization of Ti-Nb alloys. Summary of the invention

[0003] In view of the defects of the prior art, the purpose of the present invention is to provide a method for preparing a high-density Ti-Nb alloy, aiming to solve the technical problem of low density of alloys with large melting point differences prepared by traditional powder metallurgy technology, and is particularly suitable for the preparation of high-density Ti-Nb alloys with high Nb content.

[0004] To achieve the above object, the present invention provides a method for preparing a high-density Ti-Nb alloy, comprising the following steps: (1) Mixing Ti powder and Nb powder under an inert atmosphere, and pressing the mixed powder to obtain a pressed green body; (2) performing a first vacuum sintering on the pressed green body to obtain a Ti-Nb alloy with preliminary homogenization; (3) Slicing the preliminarily homogenized alloy and performing a hydrogenation treatment to obtain a hydrogenated Ti-Nb alloy; (4) Grinding the hydrogenated Ti-Nb alloy to obtain hydrogenated Ti-Nb alloy powder; (5) After the hydrogenated Ti-Nb alloy powder is pressed, it is subjected to a second vacuum dehydrogenation sintering to obtain a densified Ti-Nb alloy.

[0005] Preferably, the Ti-Nb alloy is a Ti-35Nb alloy, a Ti-40Nb alloy or a Ti-45Nb alloy.

[0006] Preferably, the first vacuum sintering in step (2) is performed by evacuating the vacuum to 10 -3 Pa or below, and then heated to the sintering temperature of 1150-1250℃ and kept warm for 3-5 hours.

[0007] Preferably, during the hydrogenation treatment in step (3), the pressure of hydrogen is maintained at -30 to -50 kPa, and the hydrogenation is carried out for 1.5 to 2.5 h.

[0008] Preferably, the second vacuum dehydrogenation sintering in step (5) is performed by evacuating the vacuum to 10 -3 Pa or below, and then heated to the sintering temperature of 1150-1250℃ and kept warm for 3-5 hours.

[0009] Preferably, in the second vacuum dehydrogenation sintering in step (5), a plurality of insulation sections are first set at 400-800°C for dehydrogenation to ensure that the hydrogen in the sample is completely removed; then the temperature is raised to a maximum of 1200°C and maintained at the highest temperature for 3-5h to achieve sintering densification and uniform diffusion of elements, and then the furnace is cooled; during the heating process, the heating rate is set to 4-5°C / min when the temperature is raised to below 1000°C, and the heating rate is set to 2-3°C / min when the temperature is raised to above 1000°C.

[0010] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art: 1. The present invention provides a method for preparing a high-density Ti-Nb alloy, which is a powder metallurgy preparation method. The method comprises the following steps: firstly, mixing Ti powder and Nb powder and then pressing the mixed powders, and then performing a first vacuum sintering to obtain a Ti-Nb alloy with preliminary homogenization; then slicing the mixed powders and performing a hydrogenation treatment to obtain a hydrogenated Ti-Nb alloy powder containing a large amount of H after ball milling; finally, the hydrogenated Ti-Nb alloy powder is pressed and then subjected to a second vacuum dehydrogenation sintering, wherein a large number of defects are generated by dehydrogenation, which is beneficial to sintering densification, and finally a densified Ti-Nb alloy is prepared.

[0011] 2. The present invention provides a method for preparing a high-density Ti-Nb alloy, wherein the alloy density reaches more than 99%, and the elements are evenly distributed, which solves the densification difficulties caused by the melting point difference between Ti and Nb, and is the key to optimizing the performance of Ti-Nb alloy. The preparation method is simple and provides an effective solution for preparing high-density and homogenized Ti-Nb alloys, promoting its application in the field of high-performance materials, and bringing new opportunities and development directions to related industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the process of preparing Ti-Nb high-density alloy by powder metallurgy of the present invention; Figure 2 This is the microscopic morphology of the Ti-35Nb alloy prepared by the conventional powder metallurgy method in Comparative Example 1; Figure 3 This is the microscopic morphology of the Ti-10Nb alloy prepared by the conventional powder metallurgy method in Comparative Example 2; Figure 4 This is the microscopic morphology of the Ti-20Nb alloy prepared by the conventional powder metallurgy method in Comparative Example 3; Figure 5 Content (a) and content (b) are the slice photos of Ti-35Nb sintered sample before and after hydrogenation in Example 1, respectively; Figure 6 This is the particle size distribution diagram of hydrogenated and crushed Ti-35Nb powder in Example 1; Figure 7 The SEM and EDS results of the surface and internal cross-section of the hydrogenated and crushed Ti-35Nb powder in Example 1; Figure 8 The XRD diagram of the mixed powder (Ti-35Nb) before sintering in step (1) of comparative example 1, the XRD diagram of the mixed powder (TiH2-35NbH) before sintering in comparative example 6, and the XRD diagram of the alloy powder (Secondary hydrogenation) after hydrogenation and before the second vacuum sintering in step (4) of example 1; Fig. 9 The SEM electron image microstructure and EDS results of the secondary sintered sample of hydrogenated Ti-35Nb alloy powder prepared in Example 1; Fig.10 These are the microscopic morphologies of the Ti-35Nb alloys prepared in Comparative Examples 1, 4, 5 and 6. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0014] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0015] Additionally, references throughout this specification to "one embodiment," "one embodiment," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase "in one embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0016] The melting points of Ti and Nb are 1668°C and 2477°C, respectively, which are quite different. Due to its high melting point, Nb is often not completely dissolved in the Ti matrix, forming undissolved Nb particles. These undissolved Nb particles not only affect the microstructure of the alloy, but also lead to the inhomogeneity of mechanical properties, thereby limiting its potential for practical application. Some literature shows that the above problems can be solved by pre-alloying powder, but pre-alloying powder usually requires multiple smelting. Therefore, it is of great significance to develop a technology for preparing TiNb high-density alloy by low-energy powder metallurgy. The present invention combines pre-alloying, hydrogenation and secondary sintering after hydrogenation to realize the process of preparing high-density and high-homogeneity TiNb alloy by powder metallurgy.

[0017] Specifically, if Figure 1 As shown, the present invention provides a powder metallurgy preparation method of a high-density Ti-Nb alloy, comprising the following steps: (1) Mixing Ti powder and Nb powder under an inert atmosphere, and pressing the mixed powder to obtain a pressed green body; (2) performing a first vacuum sintering on the pressed green body to obtain a Ti-Nb alloy with preliminary homogenization; (3) Slicing the preliminarily homogenized alloy and performing a hydrogenation treatment to obtain a hydrogenated Ti-Nb alloy; (4) Grinding the hydrogenated Ti-Nb alloy to obtain hydrogenated Ti-Nb alloy powder; (5) After the hydrogenated Ti-Nb alloy powder is pressed, it is subjected to a second vacuum dehydrogenation sintering to obtain a densified Ti-Nb alloy.

[0018] In some embodiments of the present invention, Ti powder and Nb powder with a low oxygen content of 0-150 μm are mixed and pressed, and then the first vacuum sintering is performed. The purpose of the first vacuum sintering is to make Ti and Nb form a TiNb alloy with a relatively uniform composition, and the first vacuum sintering has two functions. The first function is to make Ti with HCP structure and Nb with BCC structure form a single β-phase structure alloy. Although there are undissolved Nb particles, most of the alloy has formed a homogeneous TiNb alloy, which can help to obtain hydrogenated powder with uniform element distribution in the subsequent step; the second function is that the block alloy formed by the first sintering has more internal pores, resulting in a large specific surface area, which is easier to hydrogenate than the smelted high-density alloy, and the hydrogen pressure and time in the hydrogenation step are theoretically reduced.

[0019] The alloy obtained by the first vacuum sintering is hydrogenated and crushed to obtain a hydrogenated alloy powder with uniform element distribution, which is then pressed and subjected to a second vacuum sintering. The hydrogenated pre-alloyed powder is very brittle, and after grinding, such as ball milling, the hydrogenated pre-alloyed brittle powder is obtained. It is easy to break and fill pores during pressing, and the pressing density is high; a large number of defects are generated during sintering and dehydrogenation of the hydrogenated pre-alloyed powder, which is conducive to sintering densification; the pre-alloyed powder is already in a state of uniform element distribution, and does not require very high temperature sintering. In some embodiments, the maximum sintering temperature of the second vacuum sintering is 1200°C to achieve densification and homogenization; the sintering results in a TiNb alloy with high quality and density (99.32±0.02%) and uniform element distribution (no segregation and undissolved particles).

[0020] The method for preparing a high-density Ti-Nb alloy by powder metallurgy of the present invention is mainly aimed at Ti-Nb alloys with a high Nb content in the alloy that are prone to segregation, such as Ti-Nb alloys with a Nb mass percentage greater than or equal to 30%. In some embodiments, the Ti-Nb alloy is a Ti-35Nb alloy, a Ti-40Nb alloy or a Ti-45Nb alloy. Step (1) Weigh Ti powder and Nb powder according to the element ratio of the target Ti-Nb alloy, and then mix the powders. In some embodiments, the particle size of the Ti powder and Nb powder in step (1) is less than 200μm, and preferably less than 150μm.

[0021] The inert atmosphere or protective atmosphere of the present invention includes but is not limited to helium, neon or argon, preferably argon.

[0022] In some embodiments, the pressing in step (1) is cold isostatic pressing, the pressure of the cold isostatic pressing is 250-300 MPa, and the pressure is maintained for 1000-1500 seconds. -3Pa or less, and then heated to a sintering temperature of 1150-1250°C and kept warm for 3-5 hours. During the hydrogenation treatment in step (3), the pressure of hydrogen is maintained at -30~-50kPa, and the hydrogenation is performed for 1.5-2.5 hours. In the embodiment of the present invention, the hydrogenation treatment is carried out in a high vacuum sintering furnace to prevent elements such as oxygen and hydrogen from entering the material at high temperature, resulting in a decrease in mechanical properties. The pressure in the sintering furnace is -102kPa in the initial state. Hydrogen is introduced during the hydrogenation treatment to control the pressure at -30~-50kPa for hydrogenation operation.

[0023] In some embodiments, the ball milling in step (4) is performed under a protective atmosphere, the ball milling speed is set to 400-600 RPM, and the ball milling time is 3-8 min. The protective atmosphere is an inert gas such as argon.

[0024] In some embodiments, the pressing in step (5) is cold isostatic pressing, the cold isostatic pressing pressure is 250-300 MPa, and the pressure is maintained for 1000-1500 seconds. -3 Pa or less, and then heated to the sintering temperature of 1150-1250℃ and kept warm for 3-5 hours.

[0025] In some embodiments, in the second vacuum dehydrogenation sintering in step (5), a plurality of insulation sections are first set at 400-800°C for dehydrogenation to ensure that the hydrogen in the sample is completely removed; then the temperature is raised to a maximum of 1200°C and maintained at the highest temperature for 3-5 hours to achieve sintering densification and uniform diffusion of elements, and then the furnace is cooled; during the heating process, the heating rate is set to 4-5°C / min when the temperature is below 1000°C, and the heating rate is set to 2-3°C / min when the temperature is above 1000°C.

[0026] The present invention proposes an improved hydrogenation sintering process, i.e., a method for preparing a high-density and high-uniformity Ti-Nb alloy. In some embodiments, the density of the sintered samples reaches 99.32%, solving the bottleneck of low density of alloys with large melting point differences prepared by traditional powder metallurgy technology.

[0027] The following are comparative examples and embodiments: Comparative Example 1 The traditional metallurgical method for preparing Ti-35Nb alloy is as follows: (1) Ti powder and Nb powder with a particle size of less than 150 μm are loaded into a mixer in a mass ratio of 65:35. After gas washing, argon gas is filled in to prevent the oxygen content from increasing; (2) After mixing the powder, place it in a φ15×80 mm cylindrical rubber bag in a vacuum glove box and vibrate it, followed by cold isostatic pressing; (3) The cold isostatic pressing parameters are 280 MPa and the pressure is maintained for 1200 s to obtain a cylindrical green compact.

[0028] (4) Place the pressed green body into a vacuum sintering furnace and evacuate to 10 -3 Pa and then heated to 1200 °C, kept warm for 4 h, with a heating rate of 5 °C / min below 1000 °C and a heating rate of 3 °C / min above 1000 °C, followed by furnace cooling to obtain a Ti-35Nb once-sintered sample.

[0029] Comparative Example 1 The microstructure of the Ti-35Nb alloy prepared by conventional metallurgical method is as follows Figure 2 shown.

[0030] Comparative Example 2 The other steps are the same as those in Comparative Example 1, except that the prepared Ti-Nb alloy is Ti-10Nb, and in step (1), Ti powder and Nb powder with a particle size of less than 150 μm are charged into the mixer in a mass ratio of 90:10. The micromorphology of the prepared Ti-10Nb alloy is as follows: Figure 3 shown.

[0031] Comparative Example 3 The other steps are the same as those in Comparative Example 1, except that the prepared Ti-Nb alloy is Ti-20Nb, and in step (1), Ti powder and Nb powder with a particle size of less than 150 μm are charged into the mixer in a mass ratio of 80:20. The micromorphology of the prepared Ti-20Nb alloy is as follows: Figure 4 shown.

[0032] By comparing the microscopic morphologies of Ti-35Nb, Ti-10Nb and Ti-20Nb prepared in Examples 1 to 3, it can be found that compared with Ti-35Nb, Ti-10Nb and Ti-20Nb have relatively lower Nb contents and lighter segregation phenomena. Therefore, the secondary hydrogenation sintering improvement of the present invention is mainly aimed at Ti-Nb alloys with higher Nb contents, in order to improve their density and uniformity.

[0033] The following examples and comparative examples take Ti-35Nb with a high Nb content as an example, and propose a method for secondary hydrogenation sintering to solve the problems of low density and segregation of TiNb alloy prepared by powder metallurgy.

[0034] Example 1 The preparation method of the Ti-35Nb alloy with high Nb content and high density is carried out according to the following steps: (1) Ti and Nb powders with a particle size of less than 150 μm are charged into a mixer in a mass ratio of 65:35 for mixing. The mixer is purged before mixing to ensure that the powders are mixed under an argon atmosphere to prevent the oxygen content from increasing. After mixing, the powders are loaded into a φ15×80 mm cylindrical rubber sleeve and vibrated, followed by cold isostatic pressing. The cold isostatic pressing parameters are 280 MPa and the pressure is maintained for 1200 s to obtain a cylindrical compact.

[0035] (2) Place the pressed green body into a vacuum sintering furnace and evacuate to 10 -3 Pa, and then heated to 1200℃ for 4h, and then cooled in the furnace. The Ti-35Nb obtained at this time is a single sintered sample with poor density and uniformity.

[0036] (3) Cut the primary sintered sample into 3 mm discs using a cutting machine. Figure 5 Content (a), use sandpaper to remove the oxide layer on the surface, put it into ethanol solution for ultrasonic cleaning. Then put it into the sintering furnace for hydrogenation, first evacuate to 10 -3 Pa, heating was started, vacuum was maintained, the temperature was raised to 800℃, and then the temperature was lowered to 600℃. Hydrogen was filled in at 600℃, the pressure was maintained in the range of -30~-50kPa, and hydrogenation was carried out for 2h. Then, a saturated hydrogenated Ti-35Nb disc which was very easy to break was obtained, such as Figure 5 Content (b).

[0037] (4) Then Figure 5 The hydrogenated sample of content (b) was placed in a vacuum ball mill, filled with argon gas for protection, with a ball-to-material ratio of 5:1 and a rotation speed of 500RPM. After ball milling for 5 minutes, the sample was sieved through a 100-mesh sieve to obtain a Ti-35Nb alloy powder with uniform element distribution. The particle size distribution of the alloy powder is shown in Figure 2. Figure 6 As shown in Figure 1, the powder particle size is between 0 and 150 μm. The surface and internal cross-section of the powder particles were analyzed by EDS element scanning. The results are shown in Figure 1. Figure 7 Content (a), content (b), content (c), content (d), content (e) and content (f) show that the hydrogenated alloy powder achieves uniform distribution of Ti-35Nb alloy. Figure 8 As shown, the sample Secondaryhydrogenation is the XRD diagram of the Ti-35Nb alloy powder after ball milling in this step, indicating that the alloy powder is a single δ phase.

[0038] (5) The hydrogenated and crushed Ti-35Nb alloy powder was placed in a ∅15*80mm cylindrical rubber bag in a vacuum glove box and vibrated, followed by cold isostatic pressing; the cold isostatic pressing parameters were 280MPa and the pressure was maintained for 1200s to obtain a cylindrical green compact. The pressed green compact was placed in a vacuum sintering furnace and evacuated to 10 -3Pa, heating; heating to 450℃ and keeping for 1h, then heating to 600℃ and keeping for 1h, and finally heating to 800℃ and keeping for 1h, setting multiple insulation sections for dehydrogenation to ensure that the hydrogen in the sample is completely removed; then continue heating to 1200℃, keep for 4h, and then cool with the furnace. The heating rate is 5℃ / min below 1000℃ and 3℃ / min above 1000℃, and the Ti-35Nb secondary sintered sample is obtained.

[0039] Compared with the method of preparing pre-alloyed powder by multiple smelting, the above method significantly reduces the process steps and energy consumption. In addition, the density of the Ti-35Nb secondary sintered sample obtained by the above method reached 99.32% by the Archimedes drainage method (specifically: the density of the sintered sample ρ1 (g / cm 3 ), and then measure the density ρ2 (g / cm 3 ), the arc-melted alloy has no pores. The density of such a sample is usually regarded as the ideal density, and then ρ1 / ρ2=99.32% is calculated). The microstructure and element distribution results of the sintered sample are shown in Fig. 9 As shown in content (a), content (b) and content (c), it is not difficult to see that the elements are evenly distributed and the sintered density is high, which solves the bottleneck of low density of alloys with large melting point differences prepared by traditional powder metallurgy technology.

[0040] During the experiment, the conventional powder metallurgy method of Comparative Example 1 was also tried, but different Ti sources and Nb sources were replaced at the same time to prepare the Ti-35Nb alloy.

[0041] Comparative Example 4 The other steps are the same as those of Comparative Example 1, except that in step (1), TiH2 powder and Nb powder with a particle size of less than 150 μm are loaded into a mixer for subsequent steps, wherein the mass ratio of Ti to Nb elements is 65:35. The microstructure of the prepared Ti-35Nb alloy is as follows: Fig.10 As shown, the density is measured by the Archimedes drainage method and is 93.09%.

[0042] Comparative Example 5 The other steps are the same as those of Comparative Example 1, except that in step (1), Ti powder and NbH powder with a particle size of less than 150 μm are loaded into a mixer for subsequent steps, wherein the mass ratio of Ti to Nb elements is 65:35. The microstructure of the prepared Ti-35Nb alloy is as follows: Fig.10 As shown, the density is measured by Archimedes drainage method and is 91.78%.

[0043] Comparative Example 6 The other steps are the same as those of Comparative Example 1, except that in step (1), TiH2 powder and NbH powder with a particle size of less than 150 μm are loaded into a mixer for subsequent steps, wherein the mass ratio of Ti to Nb elements is 65:35. The microstructure of the prepared Ti-35Nb alloy is as follows: Fig.10 As shown, the density is measured by Archimedes drainage method and is 92.26%.

[0044] from Fig.10 It can be seen that the density of the Ti-35Nb alloy prepared by the traditional powder metallurgy method of one-time sintering is low, even if TiH2 powder is directly used instead of Ti powder, or NbH powder is directly used instead of Nb powder as in Comparative Examples 4 to 6, which is significantly lower than the density of the Ti-35Nb alloy obtained by two sinterings in Example 1.

[0045] Figure 8 Samples Ti-35Nb and TiH2-35NbH represent the XRD patterns of the raw material mixed powders obtained by mixing in step (1) of Comparative Example 1 and Comparative Example 6, respectively. It can be seen that the physical phase of the initial powder before densification sintering in Example 1 (single δ phase) is completely different from the physical phase of the initial mixed powder by conventional powder metallurgy method in Comparative Example 1 and Comparative Example 6.

[0046] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high-density Ti-Nb alloy, characterized in that: The steps include: (1) Mixing Ti powder and Nb powder under an inert atmosphere, and pressing the mixed powder to obtain a pressed green body; (2) performing a first vacuum sintering on the pressed green body to obtain a Ti-Nb alloy with preliminary homogenization; (3) Slicing the preliminarily homogenized alloy and performing a hydrogenation treatment to obtain a hydrogenated Ti-Nb alloy; (4) Grinding the hydrogenated Ti-Nb alloy to obtain hydrogenated Ti-Nb alloy powder; (5) After the hydrogenated Ti-Nb alloy powder is pressed, it is subjected to a second vacuum dehydrogenation sintering to obtain a densified Ti-Nb alloy.

2. The preparation method according to claim 1, characterized in that The Ti-Nb alloy is a Ti-35Nb alloy, a Ti-40Nb alloy or a Ti-45Nb alloy.

3. The preparation method according to claim 1, characterized in that: The particle sizes of the Ti powder and Nb powder in step (1) are both less than 200 μm.

4. The preparation method according to claim 1, characterized in that: The pressing in step (1) is cold isostatic pressing, the pressure of cold isostatic pressing is 250-300 MPa, and the pressure is maintained for 1000-1500 seconds.

5. The preparation method according to claim 1, characterized in that: The first vacuum sintering in step (2) is performed by evacuating the vacuum to 10 -3 Pa or below, and then heated to the sintering temperature of 1150-1250℃ and kept warm for 3-5 hours.

6. The preparation method according to claim 1, characterized in that: During the hydrogenation treatment in step (3), the pressure of hydrogen is maintained at -30 to -50 kPa, and the hydrogenation is carried out for 1.5 to 2.5 hours.

7. The preparation method according to claim 1, characterized in that: Step (4) ball milling is performed under a protective atmosphere, the ball milling speed is set to 400-600 RPM, and the ball milling time is 3-8 min.

8. The preparation method according to claim 1, characterized in that: The pressing in step (5) is cold isostatic pressing, the cold isostatic pressing pressure is 250-300 MPa, and the pressure is maintained for 1000-1500 seconds.

9. The preparation method according to claim 1, characterized in that: The second vacuum dehydrogenation sintering in step (5) is performed by evacuating the vacuum to 10 -3 Pa or below, and then heated to the sintering temperature of 1150-1250℃ and kept warm for 3-5 hours.

10. The preparation method according to claim 1, characterized in that: In the second vacuum dehydrogenation sintering in step (5), multiple insulation sections are first set at 400-800°C for dehydrogenation to ensure that the hydrogen in the sample is completely removed; then the temperature is raised to a maximum of 1200°C and maintained at the highest temperature for 3-5 hours to achieve sintering densification and uniform diffusion of elements, and then cooled with the furnace; During the heating process, the heating rate is set to 4-5°C / min when the temperature is below 1000°C, and the heating rate is set to 2-3°C / min when the temperature is above 1000°C.

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