An ordered phase strengthened titanium alloy and a powder metallurgy preparation method thereof

Abstract

This invention discloses an ordered phase-strengthened titanium alloy and its powder metallurgy preparation method, belonging to the field of titanium and titanium alloy processing technology. The preparation method includes the following steps: sponge titanium is sequentially subjected to hydrogenation treatment, mechanical ball milling, dehydrogenation treatment, and mixing with an intermediate alloy to obtain a titanium-based alloyed mixed powder, which is then subjected to cold isostatic pressing to obtain a compact; the compact is placed in a vacuum sintering furnace, first undergoing low-temperature pre-sintering, then switching to an argon protective atmosphere for high-temperature diffusion densification sintering, followed by segmental cooling to room temperature to obtain a sintered compact; the sintered compact is subjected to hot isostatic pressing, then slowly cooled to room temperature, and finally subjected to solution aging treatment to obtain an ordered phase-strengthened titanium alloy. By refining the powder through hydrogenation and milling, controlling the composition and microstructure through two-stage vacuum sintering, and controlling the phase transformation point through hot isostatic pressing, densification and microstructure are synergistically regulated, solving technical problems such as microstructure coarsening, decreased orderliness, cracking, and insufficient mechanical properties during the preparation of ordered phase-strengthened titanium alloy powder metallurgy products.

Description

Technical Field

[0001] This invention belongs to the field of titanium and titanium alloy processing technology, specifically relating to an ordered phase reinforced titanium alloy and its powder metallurgy preparation method. Background Technology

[0002] With the development of aero-engines towards higher thrust-to-weight ratios and lighter weight, powder metallurgy has become an important method for preparing complex high-performance titanium alloy components. Novel titanium alloys reinforced with Ti-Al-Sn ternary ordered phases such as Ti8AlSn and Ti4AlSn2 have become key materials for improving thrust-to-weight ratios due to their excellent high-temperature strength and creep resistance. However, these alloys face a series of technical challenges in powder metallurgy preparation: First, conventional sintering easily leads to coarsening or even re-dissolution of the ordered phase, reducing the strengthening effect; second, impurities such as oxygen and hydrogen adsorbed on the powder surface easily induce local component segregation, leading to abnormal aggregation of the ordered phase and exacerbating material brittleness; third, traditional hot isostatic pressing is usually carried out at temperatures close to or above the β phase transformation point. Although this achieves pore closure, it enhances long-range atomic diffusion, resulting in significant coarsening of grains and ordered phases, thereby weakening mechanical properties.

[0003] Existing methods struggle to achieve an effective balance between densification, microstructure uniformity, and ordered phase stability, leading to cracking or insufficient mechanical properties in the finished products. Therefore, there is an urgent need to develop a method that utilizes powder pretreatment, two-stage sintering, and phase transformation point-controlled hot isostatic pressing to achieve stable preparation of high-performance titanium alloy products. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide an ordered phase reinforced titanium alloy and its powder metallurgy preparation method. By refining the powder through hydrogenation grinding, controlling the composition and microstructure through two-stage vacuum sintering, and controlling the phase transformation point through hot isostatic pressing, densification and microstructure are synergistically regulated, thus solving the technical problems of microstructure coarsening, decreased orderliness, cracking and insufficient mechanical properties in the preparation of ordered phase reinforced titanium alloy powder metallurgy products.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a powder metallurgy method for preparing ordered phase reinforced titanium alloys, comprising the following steps: Titanium sponge is sequentially hydrogenated, mechanically ball-milled, dehydrogenated, and mixed with intermediate alloys to obtain titanium-based alloyed mixed powder, which is then cold isostatically pressed to obtain a compact. The compact is placed in a vacuum sintering furnace, first undergoing low-temperature pre-sintering, then switching to an argon protective atmosphere for high-temperature diffusion densification sintering, and finally cooling to room temperature in stages to obtain the sintered compact. The sintered billet was subjected to hot isostatic pressing at 30-80°C below the β phase transformation point and at a pressure of 140-200 MPa. It was then slowly cooled to room temperature at a rate of 0.5-2°C / min and subjected to solution aging treatment to obtain an ordered phase strengthened titanium alloy.

[0006] In one embodiment, the ordered phase strengthened titanium alloy is composed of the following components by mass percentage: Al 4%~20%, Sn 4%~35%, and small amounts of Nb, W, Si, C, Zr, Mo, and B elements, wherein the content of W is ≤10%, the content of Nb, Si, C, Zr, Mo, and B is ≤4%, and the balance is Ti and unavoidable impurity elements.

[0007] In one embodiment, the hydrogenation treatment is carried out at a temperature of 350~500℃ for 4~8 h; the mechanical ball milling process is carried out at a ball-to-material ratio of 3:1~5:1 for 6~12 h for 80~120 rpm.

[0008] In one embodiment, the dehydrogenation process is carried out at a temperature of 500-700°C for 2-4 hours.

[0009] In one embodiment, the oxygen content of the titanium-based alloyed mixed powder is ≤0.12 wt.%, and the average particle size is 5~15 μm.

[0010] In one embodiment, the cold isostatic pressing process is performed with a pressure of 300-500 MPa and a holding time of 30-60 min.

[0011] In one embodiment, the low-temperature pre-sintering is carried out under a vacuum degree ≤ 5 × 10⁻⁶. -3 The process is carried out under Pa conditions, with the temperature increased to 900-1000℃ at a rate of 2-5℃ / min, and held for 1-2 hours.

[0012] In one embodiment, during the high-temperature diffusion densification sintering, the pressure is maintained at 10~20 kPa, and the temperature is increased to 1350~1450℃ at a rate of 3~6℃ / min, and held for 2~4 h.

[0013] In one embodiment, during the segmented cooling, the temperature is first slowly cooled to 950-1000°C at a rate of 0.5-2°C / min, and then cooled to room temperature at a rate of 2-5°C / min; the heat preservation and pressure holding time for the hot isostatic pressing treatment is 2-3 hours.

[0014] The present invention also provides an ordered phase strengthened titanium alloy prepared by the powder metallurgy preparation method of the ordered phase strengthened titanium alloy described above, wherein the microstructure of the ordered phase strengthened titanium alloy contains a Ti-Al-Sn ternary ordered phase, wherein the Ti-Al-Sn ternary ordered phase is a Ti8AlSn phase and / or a Ti4AlSn2 phase.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a powder metallurgy method for preparing ordered phase-reinforced titanium alloys. Low-oxygen titanium-based alloyed mixed powders are obtained through hydrogenation grinding and dehydrogenation. A two-stage sintering process—low-temperature pre-sintering followed by high-temperature argon-protected sintering—effectively removes residual gases and volatiles, preventing impurities from inducing localized aggregation of the ordered phase. This provides a clean, segregation-free microstructure for the uniform dispersion of a small amount of ordered phase, ensuring the alloy's microstructure uniformity. The hot isostatic pressing temperature is controlled at 30-80°C below the β-phase transformation point, and the pressure is 140-200 °C. The process, using MPa, closes the residual pores from sintering while suppressing the coarsening of the ordered phase through restricted diffusion conditions, and promotes its dispersed precipitation and uniform distribution in the disordered matrix. Combined with slow cooling of 0.5~2℃ / min, it ensures a fine distribution of the ordered phase and maintains the disordered state of the matrix, thereby improving strength while maintaining plasticity and avoiding increased brittleness. Hot isostatic pressing below the phase transformation point achieves the synergistic process of alloy densification and ordered phase control. At the same time, the use of single-stage hot isostatic pressing instead of multi-stage high-temperature treatment, through the coordinated control of temperature, pressure and cooling rate, solves the technical problems of uneven distribution of ordered phase and insufficient plasticity in the preparation of disordered titanium alloy matrix with a small amount of ordered phase strengthening. It achieves an optimized balance between strength and plasticity, and the overall process is simplified and can fully adapt to the material characteristics of ordered phase strengthened titanium alloys.

[0016] Furthermore, this invention synergistically defines the parameter ranges for hydrogenation, mechanical ball milling, dehydrogenation, and cold isostatic pressing. When the hydrogenation temperature or time is below the aforementioned range, the sponge titanium becomes insufficiently embrittled, which is detrimental to subsequent fragmentation and refinement, resulting in powder with a large particle size and uneven distribution. When the hydrogenation temperature or time is above the aforementioned range, it easily leads to excessive hydrogen absorption by the powder and increases the burden on subsequent dehydrogenation. When the ball-to-material ratio, ball milling time, or ball milling speed of mechanical ball milling is below the aforementioned range, the powder refinement is insufficient, making it difficult to obtain titanium-based alloyed mixed powder with an average particle size of 5-15 μm. When it is above the aforementioned range, it easily causes cold welding of the powder, irregular particle morphology, and increased oxygen content. When the dehydrogenation temperature or time is below the aforementioned range, residual hydrogen removal is insufficient, easily causing structural defects during subsequent sintering and heat treatment. When it is above the aforementioned range, it easily causes abnormal powder growth or intensified surface oxidation. When the cold isostatic pressing pressure or holding time is lower than the above range, the compact density is insufficient and the particle contact is poor, which is not conducive to subsequent sintering densification; when it is higher than the above range, it is easy to cause stress concentration or local cracking in the compact, which affects the dimensional stability and microstructure uniformity of the product.

[0017] Furthermore, this invention provides staged control of parameters for the low-temperature pre-sintering, high-temperature diffusion densification sintering, hot isostatic pressing, and cooling processes. When the low-temperature pre-sintering temperature or holding time is below the aforementioned range, residual gases and volatiles are not sufficiently removed; when it is above the aforementioned range, initial microstructure coarsening is easily induced. When the high-temperature diffusion densification sintering temperature or holding time is below the aforementioned range, diffusion is insufficient, pores are difficult to close effectively, and the product's densification degree is low; when it is above the aforementioned range, grain growth, local aggregation of ordered phases, or coarsening are easily caused. When the argon protection pressure is below the aforementioned range, the protective effect is insufficient; when it is above the aforementioned range, it is not conducive to the further removal of residual volatiles during sintering and affects the stability of the sintering environment. When the hot isostatic pressing temperature is above the control window of 30-80°C below the β phase transformation point, long-range atomic diffusion is enhanced, easily causing ordered phase coarsening, increased matrix ordering tendency during slow cooling, and increased brittleness; when it is below this control window, residual pore closure and microstructure homogenization are insufficient. When the hot isostatic pressing pressure is below 140~200 MPa, it is difficult to effectively eliminate residual sintering porosity; above this range, it may exacerbate local stress concentration and induce microstructure instability. When the cooling rate after hot isostatic pressing is above 0.5~2 ℃ / min, it easily inhibits the uniform dispersion precipitation of the ordered phase and leads to microstructure stress accumulation; below this range, it may prolong the high-temperature residence time, increasing the risk of ordered phase coarsening and matrix ordering transformation. Attached Figure Description

[0018] Figure 1 The image shows the microstructure of the original powder prepared in Example 1 using a scanning electron microscope. Figure 2 This is a high-magnification image of the powder metallurgy product prepared in Example 2. Detailed Implementation

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0021] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0022] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0023] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0024] This invention provides an ordered phase reinforced titanium alloy and its powder metallurgy preparation method.

[0025] The provided method for preparing ordered phase reinforced titanium alloys using powder metallurgy includes the following steps: Step 1, Powder preparation and forming: Sponge titanium is hydrogenated, mechanically ball-milled, dehydrogenated, and mixed with intermediate alloy to obtain titanium-based alloyed mixed powder, which is then cold isostatically pressed to obtain a compact. Step 2, two-stage vacuum sintering: The compact is placed in a vacuum sintering furnace, firstly for low-temperature pre-sintering to remove residual gas, and then switched to a high-purity argon protective atmosphere for high-temperature diffusion densification sintering. After sintering, it is cooled to room temperature in stages to obtain the sintered compact. Step 3, Phase transformation point controlled hot isostatic pressing and post-treatment: The sintered billet is subjected to hot isostatic pressing below the β phase transformation point, then slowly cooled to room temperature, and then subjected to solution aging treatment to obtain the product.

[0026] The ordered phase-strengthened titanium alloy, by mass percentage, comprises the following components: Al 4%~20%, Sn 4%~35%, and trace amounts of Nb, W, Si, C, Zr, Mo, and B, wherein the content of W is ≤10%, and the contents of Nb, Si, C, Zr, Mo, and B are all ≤4%, with the balance being Ti and unavoidable impurity elements. The microstructure of the ordered phase-strengthened titanium alloy contains a Ti-Al-Sn ternary ordered phase, which is a Ti8AlSn phase and / or a Ti4AlSn2 phase.

[0027] In step one, the hydrogenation temperature is 350~500℃, and the hydrogenation time is 4~8 h; the ball-to-material ratio of mechanical ball milling is 3:1~5:1, the ball milling time is 6~12 h, and the ball milling speed is 80~120 rpm; the dehydrogenation temperature is 500~700℃, and the dehydrogenation time is 2~4 h; the oxygen content of the obtained titanium-based alloyed mixed powder is ≤0.12 wt.%, and the average particle size is 5~15 μm; the cold isostatic pressing pressure is 300~500 MPa, and the holding time is 30~60 min.

[0028] In step two, low-temperature pre-sintering is performed under a vacuum degree ≤5×10 -3 The process is carried out under Pa conditions, with the temperature increased to 900-1000℃ at 2-5℃ / min and held for 1-2 h; then the process is switched to high-purity argon protection, with the pressure maintained at 10-20 kPa, and the temperature is increased to 1350-1450℃ at 3-6℃ / min and held for 2-4 h; after sintering, the temperature is first slowly cooled to 950-1000℃ at 0.5-2℃ / min, and then cooled to room temperature at 2-5℃ / min.

[0029] In step three, the hot isostatic pressing temperature is 30~80℃ below the β phase transition point, the pressure is 140~200 MPa, and the holding time is 2~3 h; then it is slowly cooled to room temperature at a cooling rate of 0.5~2 ℃ / min.

[0030] A powder metallurgical preparation method for an ordered phase-reinforced titanium alloy, provided in one embodiment, includes the following steps: Step 1: Powder Preparation and Shaping Sponge titanium is hydrogenated at 350-500℃ for 4-8 hours in a hydrogen atmosphere, then mechanically ball-milled (ball-to-material ratio 3:1-5:1, 6-12 hours, 80-120 rpm) and dehydrogenated at 500-700℃ for 2-4 hours. After mixing with intermediate alloy powder, a titanium-based alloyed mixed powder with an oxygen content ≤0.12 wt.% and a particle size of 5-15 μm is obtained. The powder is then cold isostatically pressed at 300-500 MPa to obtain a compact.

[0031] Step 2: Two-stage vacuum sintering The compact is pressed under a vacuum degree ≤5×10 -3 Low-temperature pre-sintering is performed by heating at 2-5℃ / min to 900-1000℃ and holding for 1-2 hours; then switching to high-purity argon protection (10-20 kPa), heating is continued at 3-6℃ / min to 1350-1450℃ and held for 2-4 hours; then slowly cooling at 0.5-2℃ / min to 950-1000℃, and then cooling to room temperature at 2-5℃ / min to obtain the sintered blank.

[0032] Step 3: Phase change point controlled hot isostatic pressing and post-processing The sintered billet is hot isostatically pressed at 140~200MPa and 30~80℃ below the β phase transformation point for 2~3h, then slowly cooled to room temperature at 0.5~2℃ / min; finally, solution aging treatment is performed to obtain the product.

[0033] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0034] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0035] Example 1 The chemical composition of the material used in this embodiment, by mass percentage, is: Ti-5.5Al-4.5Sn-2.5W-0.5Si-0.05C, and its β phase transformation point, as measured by metallographic method, is 1050℃.

[0036] Step 1: Powder Preparation and Shaping Sponge titanium was hydrogenated at 450℃ for 6 hours in a hydrogen atmosphere, followed by mechanical ball milling (ball-to-material ratio 4:1, milling for 9 hours at 100 rpm) and dehydrogenation at 600℃ for 3 hours. After mixing with intermediate alloy powder, a titanium-based alloyed mixed powder with an oxygen content of 0.10 wt.% and an average particle size of 10 μm was obtained. The powder was then cold isostatically pressed at 400 MPa and held for 45 min to obtain a compact.

[0037] Step 2: Two-stage vacuum sintering The compact is pressed under a vacuum degree ≤5×10 -3 The temperature was increased to 950℃ at 3℃ / min and held for 1.5h for low-temperature pre-sintering; then the temperature was switched to high-purity argon protection (pressure 15 kPa), and the temperature was increased to 1400℃ at 4℃ / min and held for 3h; then the temperature was slowly cooled to 980℃ at 1.5℃ / min, and then cooled to room temperature at 3℃ / min to obtain the sintered blank.

[0038] Step 3: Phase change point controlled hot isostatic pressing and post-processing The sintered billet was hot isostatically pressed for 2.5 h at 180 MPa and 50 °C (i.e., 1000 °C) below the β phase transformation point, and then slowly cooled to room temperature at 1 °C / min. Finally, it was subjected to solution aging treatment (solution temperature β-20 °C, aging temperature 600 °C, time 12 h) to obtain the product.

[0039] The final obtained titanium alloy raw powder scanning electron microscope morphology is as follows: Figure 1 As shown, the powder has a wide particle size distribution with an average particle size of about 10 μm and no obvious large non-metallic impurities, providing a good technological foundation for subsequent forming and densification processes. The mechanical properties of the powder metallurgy products prepared based on this high-quality powder are shown in Table 1: the tensile strength of the products at room temperature is about 1060 MPa, and the yield strength is about 960 MPa; at a high temperature of 650 ℃, the products still maintain a good strength level, and the elongation can reach 34%~37%, and the reduction of area is 59%~66%, showing excellent high-temperature plasticity; at the same time, the performance indicators of the samples taken from the outside and inside of the products are very similar, indicating that the overall density and microstructure of the products are good.

[0040] Table 1 Tensile properties of powder metallurgy products in Example 1

[0041] Example 2 The chemical composition of the material used in this embodiment, by mass percentage, is: Ti-5.5Al-8.5Sn-1W-0.3Si-0.045C, and its β phase transformation point, measured by metallographic method, is 1065℃.

[0042] Step 1: Powder Preparation and Shaping Sponge titanium was hydrogenated at 400℃ for 7 h in a hydrogen atmosphere, followed by mechanical ball milling (ball-to-material ratio 5:1, milling for 10 h at 90 rpm) and dehydrogenation at 550℃ for 3.5 h. After mixing with intermediate alloy powder, a titanium-based alloyed mixed powder with an oxygen content of 0.08 wt.% and an average particle size of 8 μm was obtained. The powder was then cold isostatically pressed at 350 MPa and held for 50 min to obtain a compact.

[0043] Step 2: Two-stage vacuum sintering The compact is pressed under a vacuum degree ≤5×10 -3 The temperature was increased to 920℃ at 2.5℃ / min and held for 1.8h for low-temperature pre-sintering; then the temperature was switched to high-purity argon protection (pressure 12 kPa), and the temperature was increased to 1370℃ at 3.5℃ / min and held for 3.5h; then the temperature was slowly cooled to 960℃ at 0.8℃ / min, and then cooled to room temperature at 2.5℃ / min to obtain the sintered blank.

[0044] Step 3: Phase change point controlled hot isostatic pressing and post-processing The sintered billet was hot isostatically pressed for 3 hours at 150 MPa and 70°C (995°C) below the β phase transformation point, and then slowly cooled to room temperature at 0.6°C / min. Finally, it was subjected to solution aging treatment (solution temperature β-25°C, aging temperature 580°C, time 14 hours) to obtain the product.

[0045] The final microstructure of the titanium alloy powder metallurgy products is as follows: Figure 2 As shown, the product exhibits a relatively uniform α+β structure, with the α phase / β transformation structure having a scale of approximately 15-25 μm and clear grain boundaries. The matrix contains a small amount of fine silicide and carbide precipitates and trace amounts of residual pores, resulting in high overall density and good structural uniformity, which provides the microstructure basis for the product's excellent mechanical properties.

[0046] The tensile properties of the product are shown in Table 2: the tensile strength at room temperature is about 1100 MPa and the yield strength is about 990 MPa; the tensile strength at 650℃ is about 610 MPa and the yield strength is about 480 MPa, which also maintains a high level of high-temperature strength; at the same time, the performance indicators of the samples taken from the outside and inside of the product are very similar, indicating that the overall quality of the product is uniform and stable.

[0047] Table 2 Tensile properties of powder metallurgy products in Example 2

[0048] Example 3 The chemical composition of the material used in this embodiment, by mass percentage, is: Ti-5.0Al-4.0Sn-0.5W-0.4Si-0.04C, and its β phase transformation point, as measured by metallographic method, is 1040℃.

[0049] Step 1: Powder Preparation and Shaping Sponge titanium was hydrogenated at 450℃ for 6 hours in a hydrogen atmosphere, followed by mechanical ball milling at a ball-to-material ratio of 4:1 for 9 hours at 100 rpm. Subsequently, it was dehydrogenated at 600℃ for 3 hours. After mixing with intermediate alloy powder, a titanium-based alloyed mixed powder with an oxygen content of 0.09 wt.% and an average particle size of approximately 10 μm was obtained. The powder was then cold isostatically pressed at 400 MPa and held for 45 minutes to obtain a compact.

[0050] Step 2: Two-stage vacuum sintering The compact is pressed under a vacuum degree ≤5×10 -3 Under Pa conditions, the temperature was increased to 950℃ at 3℃ / min and held for 1.5h for low-temperature pre-sintering; then, the temperature was switched to high-purity argon protection, the pressure was maintained at 15 kPa, and the temperature was increased to 1400℃ at 4℃ / min and held for 3h; after sintering, the temperature was slowly cooled to 980℃ at 1℃ / min and then cooled to room temperature at 3℃ / min to obtain the sintered blank.

[0051] Step 3: Hot isostatic pressing verification near the lower limit of the phase transition point The sintered blank was hot isostatically pressed for 2.5 hours at 960°C (80°C below the β phase transformation point) and 170 MPa. It was then slowly cooled to room temperature at a rate of 1°C / min. Finally, a solution aging treatment was performed at a solution temperature of 20°C below the β phase transformation point, i.e., a solution temperature of 1020°C before aging, an aging temperature of 600°C, and a time of 12 hours to obtain the finished product.

[0052] The tensile properties of the final powder metallurgy products are shown in Table 3. The resulting products still have high density and good strength and plasticity, indicating that pore closure and microstructure homogenization can still be achieved near the lower HIP temperature boundary by matching appropriate pressure and cooling rate.

[0053] Table 3 Tensile properties of powder metallurgy products in Example 3

[0054] Example 4 The chemical composition of the material used in this embodiment, by mass percentage, is: Ti-6.5Al-6.5Sn-1.5W-0.3Si-0.05C, and its β phase transformation point, measured by metallographic method, is 1080℃.

[0055] Step 1: Powder Preparation and Shaping Sponge titanium was hydrogenated at 450℃ for 6 hours in a hydrogen atmosphere, followed by mechanical ball milling at a ball-to-material ratio of 4:1 for 9 hours at 100 rpm. Subsequently, it was dehydrogenated at 600℃ for 3 hours. After mixing with intermediate alloy powder, a titanium-based alloyed mixed powder with an oxygen content of 0.10 wt.% and an average particle size of approximately 9 μm was obtained. The powder was then cold isostatically pressed at 400 MPa and held for 45 minutes to obtain a compact.

[0056] Step 2: Two-stage vacuum sintering The compact is pressed under a vacuum degree ≤5×10 -3 Under Pa conditions, the temperature was increased to 950℃ at 3℃ / min and held for 1.5h for low-temperature pre-sintering; then, the temperature was switched to high-purity argon protection, the pressure was maintained at 15 kPa, and the temperature was increased to 1400℃ at 4℃ / min and held for 3h; after sintering, the temperature was slowly cooled to 980℃ at 1℃ / min and then cooled to room temperature at 3℃ / min to obtain the sintered blank.

[0057] Step 3: Phase change point controlled hot isostatic pressing and post-processing The sintered billet was hot isostatically pressed for 2.5 hours at 1050°C (30°C below the β phase transformation point) and 170 MPa. It was then slowly cooled to room temperature at a rate of 1°C / min. Finally, it underwent solution aging treatment at 1060°C (20°C below the β phase transformation point) and 600°C for 12 hours to obtain the finished product.

[0058] The tensile properties of the final powder metallurgy products are shown in Table 4: due to the higher temperature, densification and diffusion homogenization are more complete, and the room temperature and high temperature strengths are slightly higher; however, due to the higher Al and Sn content and the enhanced tendency of ordered phase precipitation, the plasticity is slightly lower, but still within a reasonable range.

[0059] Table 4 Tensile properties of powder metallurgy products in Example 4

[0060] Comparative Example 1: HIP pressure exceeds the upper limit The comparative example uses the same chemical composition as Example 1 (Ti-5.5Al-4.5Sn-2.5W-0.5Si-0.05C), with a β phase transition point of 1050℃.

[0061] Except for the hot isostatic pressing pressure, the other steps are the same as in Example 1. The hot isostatic pressing conditions are: temperature 1000℃, i.e. 50℃ below the β phase transition point, pressure 240 MPa, heat and pressure holding for 2.5h, followed by slow cooling to room temperature at 1℃ / min, and then the same solution aging treatment.

[0062] The tensile properties of the final powder metallurgy products are shown in Table 5. Although the pore closure ability is enhanced after the pressure exceeds 200 MPa, excessively high HIP pressure may exacerbate the strain unevenness in the local closed-pore collapse zone, promote the aggregation of precipitates or the evolution of micro-defects near the grain boundary, and lead to a decrease in plasticity.

[0063] Table 5 Tensile properties of powder metallurgy products in Comparative Example 1

[0064] Comparative Example 2: Excessive cooling rate after HIP The comparative example uses the same chemical composition as Example 1 (Ti-5.5Al-4.5Sn-2.5W-0.5Si-0.05C), with a β phase transition point of 1050℃.

[0065] Except for the cooling rate after hot isostatic pressing, the other steps are the same as in Example 1. The hot isostatic pressing conditions are: temperature 1000℃, i.e. 50℃ below the β phase transition point, pressure 180 MPa, and holding at the temperature and pressure for 2.5h; then cooling to room temperature at 5℃ / min, and then performing the same solution aging treatment.

[0066] Due to the rapid cooling rate, localized cracking occurred in the material, reducing the yield. The tensile properties of the final powder metallurgy products are shown in Table 6: when the cooling rate exceeds 2℃ / min, rapid cooling induces residual stress, microcracks, or pore / interface defects, leading to a decrease in plasticity and high-temperature tensile properties.

[0067] Table 6 Tensile properties of powder metallurgy products in Comparative Example 2

[0068] In summary, this invention provides a powder metallurgy preparation method for ordered phase-reinforced titanium alloys. The method includes: hydrogenating sponge titanium, mechanically ball milling and dehydrogenating it, then mixing it with intermediate alloy powder to obtain a low-oxygen titanium-based alloyed mixed powder, followed by cold isostatic pressing; subjecting the pressed billet to two-stage vacuum sintering, i.e., firstly, low-temperature pre-sintering to remove residual gases, then switching to high-purity argon protection for high-temperature diffusion densification sintering, followed by segmented cooling to obtain a sintered billet; subjecting the sintered billet to hot isostatic pressing below the β-phase transformation point, then slowly cooling to room temperature, and finally solution aging to obtain the finished product. This invention effectively solves problems such as ordered phase coarsening, impurity-induced brittleness, and insufficient plasticity by using hydrogenation and milling to refine the powder, two-stage sintering to control microstructure uniformity, and hot isostatic pressing below the β-phase transformation point to achieve synergistic control of densification and ordered phase dispersion precipitation, thus obtaining high-performance powder metallurgy products with a good balance of strength and plasticity.

[0069] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A powder metallurgy preparation method for ordered phase reinforced titanium alloys, characterized in that, Includes the following steps: Titanium sponge is sequentially hydrogenated, mechanically ball-milled, dehydrogenated, and mixed with intermediate alloys to obtain titanium-based alloyed mixed powder, which is then cold isostatically pressed to obtain a compact. The compact is placed in a vacuum sintering furnace, first undergoing low-temperature pre-sintering, then switching to an argon protective atmosphere for high-temperature diffusion densification sintering, and finally cooling to room temperature in stages to obtain the sintered compact. The sintered billet was subjected to hot isostatic pressing at 30-80°C below the β phase transformation point and at a pressure of 140-200 MPa. It was then slowly cooled to room temperature at a rate of 0.5-2°C / min and subjected to solution aging treatment to obtain an ordered phase strengthened titanium alloy.

2. The powder metallurgy preparation method of an ordered phase-reinforced titanium alloy according to claim 1, characterized in that, The ordered phase strengthened titanium alloy is composed of the following components by mass percentage: Al 4%~20%, Sn 4%~35%, and small amounts of Nb, W, Si, C, Zr, Mo, and B elements, wherein the content of W is ≤10%, and the contents of Nb, Si, C, Zr, Mo, and B are all ≤4%, with the balance being Ti and unavoidable impurity elements.

3. The powder metallurgy preparation method of an ordered phase reinforced titanium alloy according to claim 1, characterized in that, In the hydrogenation treatment, the temperature is 350~500℃ and the hydrogenation time is 4~8 h; in the mechanical ball milling, the ball-to-material ratio is 3:1~5:1, the ball milling time is 6~12 h, and the ball milling speed is 80~120 rpm.

4. The powder metallurgy preparation method of an ordered phase-reinforced titanium alloy according to claim 1, characterized in that, In the dehydrogenation process, the temperature is 500~700℃ and the time is 2~4 h.

5. The powder metallurgy preparation method of an ordered phase-reinforced titanium alloy according to claim 1, characterized in that, The oxygen content of the titanium-based alloyed mixed powder is ≤0.12 wt.%, and the average particle size is 5~15 μm.

6. The powder metallurgy preparation method of an ordered phase-reinforced titanium alloy according to claim 1, characterized in that, In the cold isostatic pressing process, the pressure is 300~500 MPa and the holding time is 30~60 min.

7. The powder metallurgy preparation method of an ordered phase-reinforced titanium alloy according to claim 1, characterized in that, The low-temperature pre-sintering is carried out under a vacuum degree ≤5×10 -3 The process is carried out under Pa conditions, with the temperature increased to 900-1000℃ at a rate of 2-5℃ / min, and held for 1-2 hours.

8. The powder metallurgy preparation method of an ordered phase-reinforced titanium alloy according to claim 1, characterized in that, During the high-temperature diffusion densification sintering, the pressure is maintained at 10~20 kPa, and the temperature is increased to 1350~1450℃ at a rate of 3~6℃ / min, and held for 2~4 h.

9. A powder metallurgy preparation method for ordered phase-reinforced titanium alloy according to claim 1, characterized in that, In the segmented cooling process, the temperature is first slowly cooled to 950-1000℃ at a rate of 0.5-2℃ / min, and then cooled to room temperature at a rate of 2-5℃ / min; the heat preservation and pressure holding time for the hot isostatic pressing treatment is 2-3 hours.

10. An ordered phase reinforced titanium alloy, characterized in that, The ordered phase reinforced titanium alloy is prepared by powder metallurgy according to any one of claims 1 to 9. The microstructure of the ordered phase reinforced titanium alloy contains a Ti-Al-Sn ternary ordered phase, wherein the Ti-Al-Sn ternary ordered phase is Ti8AlSn phase and / or Ti4AlSn2 phase.

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