Low-oxygen fully-compact titanium alloy powder metallurgy method

Abstract

The invention discloses a low-oxygen fully-compact titanium alloy powder metallurgy method. The method comprises the steps that titanium alloy powder with the low interstitial element content is provided; forming under a protective atmosphere to obtain a green body; performing vacuum sintering; and then high-pressure inert gas is introduced for pressure sintering. A preferable scheme comprises powder particle size grading, a specific forming mode, atmosphere purity control, green body preservation time limit, interstitial element content mathematical relationship and powder preheating and activating treatment. The invention also relates to the low-oxygen fully-dense titanium alloy product prepared by the method. According to the method, densification is effectively promoted and oxidation is inhibited under the action of vacuum and air pressure, low-oxygen control of the titanium alloy structural part under the full-densification condition is achieved, the subsequent hot working procedure is omitted, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, and specifically to a low-oxygen fully dense titanium alloy powder metallurgy method. Background Technology

[0002] Titanium alloys are widely used in aerospace, medical devices, and chemical equipment due to their excellent specific strength, corrosion resistance, and biocompatibility. However, traditional melting and forging processes for preparing titanium alloys suffer from complex procedures, low material utilization, and high costs, limiting their wider application. Therefore, powder metallurgy, as a near-net-shape forming process, is gradually becoming an important direction in titanium alloy preparation.

[0003] Currently, common titanium alloy powder metallurgy methods mainly include molding-sintering, cold isostatic pressing-sintering, and powder injection molding. While these methods have certain advantages in forming complex structures and saving materials, a key bottleneck remains in practical applications: achieving full densification of the material. Typically, titanium alloy products obtained through traditional sintering processes only achieve a relative density of 95% to 99%, and residual internal porosity defects significantly reduce their mechanical properties, especially fatigue performance and toughness, making it difficult to meet the requirements for high-strength structural components.

[0004] The root cause of this problem lies in the physical metallurgical properties of titanium alloys. On the one hand, during solid-state sintering, "sintering necks" easily form between powder particles, hindering sufficient atomic diffusion and effective pore filling. On the other hand, titanium is chemically reactive and readily reacts with oxygen to form a stable titanium oxide film that covers the powder surface, further inhibiting the densification process. To improve density, existing technologies typically involve increasing the sintering temperature or extending the holding time, but this leads to grain coarsening and an increase in the content of interstitial elements (such as oxygen and nitrogen), thereby impairing the material's mechanical properties and service reliability.

[0005] Therefore, how to achieve full densification of titanium alloy powder metallurgy products while maintaining low oxygen content and fine grain structure has become a key problem that urgently needs to be solved in this technical field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing fully dense titanium alloy powder with low oxygen content.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows.

[0008] A low-oxygen, fully dense titanium alloy powder metallurgy method includes the following steps: S100 provides titanium alloy powder with an oxygen content ≤1800ppm, a nitrogen content ≤300ppm, and a hydrogen content ≤200ppm; S200. The titanium alloy powder is formed in an inert atmosphere or vacuum environment to obtain a green blank. S300. The green blank is placed in a sintering furnace and sintered in a vacuum environment at a temperature range of 1100℃~1300℃, and held for 1~3 hours. S400, Pressure Sintering: After the vacuum sintering step, inert gas is introduced into the sintering furnace to maintain the pressure at 2MPa~20MPa, and the temperature is maintained at 1100℃~1300℃ for 2~4 hours.

[0009] As a preferred technical solution, the titanium alloy powder is at least one of TC4, TA0, TA1, TA2, TC11, and TB6 titanium alloy powders, and its powder particle size is ≤108μm.

[0010] As a preferred technical solution, the titanium alloy powder includes at least two powders with different particle sizes, namely fine powder with a particle size of 0~25μm and coarse powder with a particle size of 50~100μm, and the fine powder and coarse powder are mixed in a weight ratio of 2:8~8:2.

[0011] As a preferred technical solution, the forming process is cold isostatic pressing, and the green billet is a solid bar with a density of 3.2~3.6 g / cm³. 3 .

[0012] As a preferred technical solution, the forming process is rolling, and the green billet is a sheet or strip with a density of 3.8~4.0 g / cm³. 3 .

[0013] As a preferred technical solution, the inert gas is high-purity argon or high-purity helium, with a purity of not less than 99.99%.

[0014] As a preferred technical solution, the green blank must be stored in a vacuum or inert gas protective environment after forming, and the time interval from the completion of forming to the start of sintering shall not exceed 24 hours.

[0015] As a preferred technical solution, the oxygen content (O), nitrogen content (N) and hydrogen content (H) of the titanium alloy powder must satisfy the following relationship: O+2N+3H≤2500, and 2≤[O / (N+H)]≤5, where the unit is ppm.

[0016] As a preferred technical solution, before the forming process, the titanium alloy powder is subjected to a vacuum of 200~400℃ and a vacuum degree not exceeding 1×10⁻⁶. -2Preheating is performed under Pa conditions for 0.5 to 2 hours, followed by cooling to below 50°C in a vacuum environment, and then immediately forming.

[0017] A low-oxygen, fully dense titanium alloy, processed using at least one of the above-mentioned technical features via powder metallurgy, has a product density ≥ 4.42 g / cm³. 3 The porosity was analyzed using electron microscopy and was ≤0.1%; the oxygen content of the product was ≤3000ppm.

[0018] The advantages and beneficial effects of this invention lie in the organic combination of vacuum degassing and pressure densification in the same thermal cycle. During the vacuum sintering stage, the system creates and maintains a high vacuum environment, reducing the oxygen partial pressure and inhibiting the oxidation reaction of titanium, while simultaneously providing an efficient diffusion channel for gases and volatile impurities adsorbed on the powder surface. Subsequently, during the pressure sintering stage, the introduced high-pressure inert gas applies isotropic isostatic pressure to the sintered body, enhancing the contact stress between powder particles and promoting surface energy-driven mass migration, thereby efficiently eliminating residual closed pores and achieving near-theoretical densification.

[0019] Furthermore, this invention systematically cuts off the introduction of oxygen through a closed-loop oxygen control process, encompassing raw material pretreatment, forming environment control, and sintering atmosphere management. This ensures that the final product has a low interstitial element content and a uniform, fine lamellar α-structure. This not only makes the product's mechanical properties comparable to those of traditional melting and forging processes but also eliminates expensive and time-consuming subsequent hot working procedures, thereby reducing costs. Detailed Implementation

[0020] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below. It is to be understood that the specific embodiments described herein are merely illustrative of this application and not intended to limit it. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0021] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly or implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] This invention provides a low-oxygen, fully dense titanium alloy powder metallurgy method. Through a precise, closed-loop process for oxygen control and densification, it overcomes the long-standing problems of insufficient density and interstitial element contamination in titanium alloy powder metallurgy. The method includes the following steps: S100 provides titanium alloy powder with low interstitial element content; S200, the powder is shaped into a green body under an inert atmosphere or vacuum protection; S300, Vacuum sintering of the green blank; S400: Based on vacuum sintering, high-pressure inert gas is introduced for pressure sintering.

[0024] In step S100, the requirements for the interstitial element content of the titanium alloy powder include: oxygen content ≤1800ppm, nitrogen content ≤300ppm, and hydrogen content ≤200ppm. Titanium alloys have an extremely high affinity for interstitial elements (especially oxygen). Even trace amounts of oxygen can dissolve in the α-Ti lattice, causing significant lattice distortion and leading to a sharp decrease in the material's plasticity and toughness (i.e., "oxygen embrittlement"). Conventional powder metallurgy processes often fail to adequately control the purity of raw materials or involve secondary oxygen absorption in subsequent processes, resulting in the final product's oxygen content far exceeding the allowable value. This fails to meet the stringent requirements for material plasticity and fatigue performance in fields such as aerospace and medical devices. This invention controls the interstitial elements in the titanium alloy powder during material selection, combined with subsequent full-process oxygen control measures, laying the foundation for achieving low-oxygen products with an oxygen content ≤3000ppm.

[0025] Step S200 requires the titanium alloy powder to be formed in an inert atmosphere or vacuum environment to obtain a green compact, preventing the powder from reacting with moisture and oxygen in the environment during the forming process with its large specific surface area. This invention isolates atmospheric pollution by completing the powder loading, transfer, and pressing in a glove box (oxygen content <0.1ppm, water content <0.1ppm) or a sealed chamber filled with high-purity inert gas. The formed green compact must be stored in a vacuum or inert gas protected environment, and the time interval from the completion of forming to the start of sintering in step S300 should not exceed 24 hours, minimizing the absorption of moisture and oxygen from the residual trace atmosphere by the highly reactive green compact surface due to physical and chemical adsorption.

[0026] Regarding the forming method, the present invention provides two preferred but non-limiting paths: cold isostatic pressing and powder rolling.

[0027] Cold isostatic pressing is suitable for preparing large-sized, isotropic, near-net-shape solid bars or blocks. The specific procedure involves sealing titanium alloy powder in a flexible (such as rubber or plastic) mold, then placing it in a high-pressure vessel and applying isotropic ultra-high pressure (200-400 MPa) through a liquid medium (usually oil or water). This pressure causes plastic deformation and mechanical interlocking of the powder particles, resulting in a density of 3.2~3.6 g / cm³. 3 The density range is critical: if the green body density is below 3.2 g / cm³... 3 If the initial porosity is too high, subsequent sintering and densification will be extremely difficult, and isolated closed pores are likely to remain; if the density is higher than 3.6 g / cm³, the density will be too low. 3 For irregular powders, this is close to the cold pressing limit, which may cause mold damage or delamination of the green body.

[0028] Powder rolling is particularly suitable for producing thin sheets and strips. The process involves feeding powder into the gap between two relatively rotating rolls, where the pressure of the rolls continuously shapes it into a strip. This method yields green blanks with a high density, reaching 3.8–4.0 g / cm³. 3 This is because in addition to the pressing force, the rolling process is also accompanied by strong shearing force, which helps to break the "arch bridge effect" of the powder and achieve a denser packing.

[0029] Step S300 is vacuum sintering, which is carried out in a vacuum environment at a temperature range of 1100℃ to 1300℃ and held for 1 to 3 hours. In this extremely low oxygen partial pressure environment, high-temperature-driven atomic diffusion achieves metallurgical bonding and initial densification between powder particles. The functions of the vacuum environment include, but are not limited to: completely eliminating oxygen to prevent titanium oxidation at high temperatures; and acting as a powerful driving force to remove gases adsorbed on the powder surface and volatile impurities remaining inside the powder (such as MgCl2 obtained by hydrogenation-dehydrogenation). These gases would remain in the pores during atmospheric pressure or low-vacuum sintering, hindering densification and contaminating the material. The sintering temperature of 1100℃ to 1300℃ is chosen because this range is higher than the β-phase transformation point (approximately 995℃) of common titanium alloys such as TC4, where the atomic diffusion rate is accelerated, which is beneficial for rapid densification. Holding for 1 to 3 hours ensures sufficient heat and material diffusion. Too low a temperature or too short a time will result in insufficient sintering and low density; while too high a temperature or too long a time will cause the rapid growth of β grains, deteriorate the mechanical properties of the material, and increase energy consumption and equipment burden.

[0030] Step S400 is pressure sintering. After the vacuum sintering step, inert gas is introduced into the sintering furnace to maintain the pressure at 2MPa~20MPa, and the temperature is maintained at 1100℃~1300℃ for 2~4 hours. After the initial framework and pore channels are formed by vacuum sintering, the applied isostatic gas pressure is transmitted through the surface of the green body to the interior, applying a huge static pressure to the unclosed pores. At high temperatures, this pressure is sufficient to drive various densification mechanisms. Densification mechanisms include, but are not limited to, grain boundary slip and grain rearrangement; plastic flow induced by dislocation climb, causing the material to fill the pore regions; and diffusion creep, where vacancies preferentially diffuse from the pore surface to the grain boundary under the pressure gradient, thereby achieving full densification (relative density >99.9%).

[0031] The main reasons why conventional powder metallurgy processes do not adopt or find it difficult to effectively apply this technology are: titanium alloy sintering mainly relies on diffusion, and external pressure has limited effect and may damage the billet; closed sintering furnaces capable of withstanding both high temperature and high pressure are expensive; furthermore, in process control, the matching of pressure, temperature, and time requires precise control, otherwise the effect will be poor or the billet will be deformed. Therefore, to a certain extent, pressure sintering has created a technological bias.

[0032] Traditionally, titanium alloys are considered strong and tough materials, maintaining high yield strength even at sintering temperatures. Conventional low-pressure methods struggle to induce effective plastic flow, while high-pressure methods can easily cause shear failure or macroscopic deformation in fragile green blanks (especially low-density green blanks) during the early densification stage. This invention utilizes a vacuum sintering process to pre-form a rigid framework with sufficient strength and interconnected pores in the green blank, typically achieving a relative density of 92%-95%. This pre-densified framework is sufficient to withstand subsequent applied pressure, preventing the risk of the green blank collapsing in the initial stage when its strength is lowest.

[0033] This invention reveals that in the specific high-temperature range of 1100-1300℃ (for alloys such as TC4, which have already entered the β single-phase region), the rheological stress of titanium alloys decreases while their plasticity increases dramatically. Under these conditions, a static pressure of 2-20 MPa is sufficient to exceed the high-temperature rheological stress threshold of the material, thereby efficiently activating bulk densification mechanisms such as dislocation climb-controlled plastic flow and diffusion creep, rather than relying solely on surface mechanisms such as interfacial diffusion and grain boundary diffusion as in traditional sintering.

[0034] This invention, through extensive experimentation, determined a pressure window of 2–20 MPa: below 2 MPa, the driving force for plastic flow is insufficient, making it difficult to eliminate micropores; above 20 MPa, the requirements for equipment and operating costs increase dramatically, while the densification gain tends to plateau, resulting in poor economic efficiency. Simultaneously, holding the material at room temperature for 2–4 hours ensures that the pressure has sufficient time to act on the material, completing the creep and plastic flow processes.

[0035] In some embodiments, the inert gas is high-purity argon or high-purity helium, with a purity of not less than 99.99%. Using a high-purity inert gas is to avoid introducing new sources of contamination. If the gas purity is insufficient, trace amounts of O2, H2O, N2, etc., will react with titanium under high temperature and pressure, not only ruining the entire process but potentially even degrading performance due to internal oxidation / nitriding. Argon is the preferred choice due to its chemical inertness, relatively low cost, and higher density than air. Helium has higher thermal conductivity, which may be beneficial for temperature uniformity in some cases, but it is more expensive.

[0036] In some embodiments, the oxygen (O), nitrogen (N), and hydrogen (H) content of the titanium alloy powder must satisfy the following relationship: O + 2N + 3H ≤ 2500, and 2 ≤ [O / (N + H)] ≤ 5, where the unit is ppm. This relationship allows for more precise control of the raw material quality, and the values ​​before the content of each element in the formula are proportionality coefficients.

[0037] The proportions of each interstitial element, derived from experimental experience, are based on the relative impact of the atomic diameter of the interstitial element and its lattice distortion and diffusion behavior in titanium alloys on the degree of ductility impairment. Oxygen exists mainly as an interstitial solid solution in titanium alloys, causing moderate lattice distortion. However, oxygen has high solubility in α-Ti and a moderate diffusion coefficient, making its ductility impairment relatively controllable. Nitrogen atoms have a larger diameter, causing greater lattice distortion in titanium lattices due to the high mismatch between nitrogen atom size and interstitial size. This leads to greater stress concentration and lattice expansion, making its ductility impairment more severe than that of oxygen. Hydrogen atoms have the smallest diameter, but their diffusion coefficient in titanium lattices is extremely high. Although hydrogen causes relatively small lattice expansion, its diffusivity and aggregation make it the most harmful to ductility. The different proportions allow the harmful effects of the three interstitial elements to be fully amplified and considered.

[0038] The limit of O+2N+3H≤2500 primarily considers the harmful effects of nitrogen and hydrogen on plasticity, which are generally considered more detrimental than oxygen. This imposes stricter requirements on the overall purity of the raw materials than the upper limit for a single element. The control of 2≤[O / (N+H)]≤5 limits the relative dominance of oxygen among the total harmful interstitial elements. An excessively high O / (N+H) ratio may indicate that oxygen contamination is the primary problem, with more pronounced solid solution strengthening and embrittlement effects. By setting this upper limit, the composition of harmful elements in the raw materials is kept relatively balanced, avoiding the extreme adverse effects of a single element.

[0039] It is worth noting that among the above limitations, the solid solution strengthening effect is weakened when the oxygen content is too low. Titanium alloys with no oxygen or extremely low oxygen content will have lower strength and hardness. Trace amounts of oxygen can promote the bulk diffusion of titanium atoms at high temperatures to some extent by forming thermodynamically balanced vacancies. When the oxygen content is too low, the contribution of this diffusion channel is weakened, which may slightly delay the growth of the sintering neck and the shrinkage rate of the pores. To achieve the same densification effect, a higher sintering temperature or a longer holding time may be required, but this has not yet been verified in the testing process. Nevertheless, it should be pointed out that the lower limit of 2≤O / (N+H) set in this invention is based on the utilization of the dual role of oxygen, rather than a compromise with impurity elements.

[0040] In some embodiments, a powder surface activation step is added before the forming process, in which the titanium alloy powder is preheated at 200~400°C under vacuum conditions and held for 0.5~2 hours, then cooled to below 50°C under vacuum conditions, and then immediately subjected to the forming process.

[0041] Conventional storage and operating environments cannot completely prevent the adsorption of monolayer or multilayer water vapor on powder surfaces. This adsorbed water decomposes during the initial heating phase of subsequent sintering, generating H2 and reactive [O], leading to a localized increase in oxygen content. The powder surface activation step, conducted under vacuum, provides gentle heat sufficient to effectively desorb these firmly adsorbed water molecules and remove them through the vacuum system. Too low a temperature or too short a time will yield poor results; too high a temperature (e.g., close to the recrystallization temperature) may cause slight sintering ("hard agglomeration") on the powder surface, negatively impacting formability and final sintering performance.

[0042] In some embodiments, the titanium alloy powder is at least one of TC4, TA0, TA1, TA2, TC11, and TB6 titanium alloy powders, and its powder particle size is ≤108 μm. This mainly includes, but is not limited to, industrially pure titanium (TA series), α+β type titanium alloys (TC4, TC11), and metastable β type titanium alloys (TB6). A powder particle size ≤108 μm ensures sufficient specific surface area to drive sintering.

[0043] In some embodiments, the titanium alloy powder comprises at least two powders with different particle sizes: fine powder (0-25 μm) and coarse powder (50-100 μm), which are mixed at a weight ratio of 2:8 to 8:2. Powder gradation technology is employed simultaneously. The fine powder fills the voids between the coarse powders, improving the initial packing density and uniformity of the green body. Higher green body density means shorter atomic diffusion paths and fewer pores to eliminate, facilitating the achievement of full densification at lower temperatures, shorter times, or lower pressures. Different mixing ratios (2:8 to 8:2) provide a flexible process window for controlling green body density, sintering shrinkage, and the mechanical properties of the final product.

[0044] This invention also provides a low-oxygen, fully dense titanium alloy prepared by the above method, the density of which is ≥4.42 g / cm³. 3 (For TC4, the density is close to the theoretical density); electron microscopy analysis shows a porosity of ≤0.1%; the oxygen content of the product is ≤3000ppm. This product has a combination of mechanical properties comparable to or even better than those of traditional melting and forging processes, and its grain structure is fine and uniform, meeting the requirements of high-end structural components.

[0045] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited to the embodiments.

[0046] Example 1 A low-oxygen, fully dense titanium alloy powder metallurgy method includes the following steps: S100. Provide titanium alloy powder, wherein the titanium alloy powder is TC4 titanium alloy powder, with an oxygen content of 1500ppm, a nitrogen content of 200ppm, a hydrogen content of 150ppm, and a powder particle size ≤108μm.

[0047] S200. The titanium alloy powder is cold isostatically pressed under an inert atmosphere to obtain a green billet, which is a solid bar with a density of 3.4 g / cm³. 3 .

[0048] S300. The green blank is placed in a sintering furnace and sintered at 1150°C under vacuum, and held for 2 hours.

[0049] S400. After the vacuum sintering step, high-purity argon gas with a purity of 99.99% is introduced into the sintering furnace to maintain the pressure at 5MPa and continue to be held at 1150°C for 3 hours.

[0050] The properties of the product obtained in this embodiment are as follows: the product density is 4.43 g / cm³. 3The porosity is 0.08%; the oxygen content is 2800 ppm; the tensile strength is 920 MPa, the yield strength is 820 MPa, and the elongation is 15%.

[0051] Example 2 A low-oxygen, fully dense titanium alloy powder metallurgy method includes the following steps: S100. Provide titanium alloy powder, wherein the titanium alloy powder is TA1 titanium alloy powder, with an oxygen content of 1600ppm, a nitrogen content of 250ppm, a hydrogen content of 180ppm, and a powder particle size ≤108μm.

[0052] S200. The titanium alloy powder is rolled into a green billet under vacuum to obtain a sheet or strip with a density of 3.9 g / cm³. 3 .

[0053] S300. The green blank is placed in a sintering furnace and sintered at 1250°C under vacuum, and held at that temperature for 1.5 hours.

[0054] S400. After the vacuum sintering step, high-purity argon gas with a purity of 99.99% is introduced into the sintering furnace to maintain the pressure at 15MPa and continue to be held at 1250°C for 2.5 hours.

[0055] The properties of the product obtained in this embodiment are as follows: the product density is 4.44 g / cm³. 3 The porosity is 0.06%; the oxygen content is 2900 ppm; the tensile strength is 1050 MPa, the yield strength is 900 MPa, and the elongation is 10%.

[0056] Example 3 A low-oxygen, fully dense titanium alloy powder metallurgy method includes the following steps: S100. Provide titanium alloy powder, which includes two types of TC4 titanium alloy powder with different particle sizes: fine powder with a particle size of 0-25μm, an oxygen content of 1800ppm, a nitrogen content of 300ppm, and a hydrogen content of 200ppm; and coarse powder with a particle size of 50-100μm, an oxygen content of 1300ppm, a nitrogen content of 200ppm, and a hydrogen content of 150ppm; the fine powder and coarse powder are mixed at a weight ratio of 5:5.

[0057] S200. The mixed titanium alloy powder is cold isostatically pressed under an inert atmosphere to obtain a green billet, which is a solid bar with a density of 3.5 g / cm³. 3 .

[0058] S300. The green blank is placed in a sintering furnace and sintered at 1200°C under vacuum, and held at that temperature for 2.5 hours.

[0059] S400. After the vacuum sintering step, high-purity argon gas with a purity of 99.99% is introduced into the sintering furnace to maintain the pressure at 10MPa and continue to be kept at 1200℃ for 3 hours.

[0060] The properties of the product obtained in this embodiment are as follows: the product density is 4.45 g / cm³. 3 The porosity is 0.07%; the oxygen content is 2700 ppm; the tensile strength is 950 MPa, the yield strength is 850 MPa, and the elongation is 16%.

[0061] Example 4 A low-oxygen, fully dense titanium alloy powder metallurgy method includes the following steps: S100. Provide titanium alloy powder, which comprises two types of TC11 titanium alloy powder with different particle sizes: fine powder with a particle size of 0-25 μm, an oxygen content of 1700 ppm, a nitrogen content of 250 ppm, and a hydrogen content of 180 ppm; and coarse powder with a particle size of 50-100 μm, an oxygen content of 1200 ppm, a nitrogen content of 200 ppm, and a hydrogen content of 150 ppm; the fine powder and coarse powder are mixed at a weight ratio of 6:4. The oxygen, nitrogen, and hydrogen contents of the titanium alloy powder satisfy the relationship: O + 2N + 3H = 2000, and O / (N + H) = 3. Before forming, the titanium alloy powder is subjected to a vacuum of 1×10⁻⁶ at 300°C. -2 Preheating is performed under Pa conditions, and the temperature is maintained for 1 hour. Then, the temperature is cooled to 40°C in a vacuum environment, and then the forming process is performed immediately.

[0062] S200. The mixed titanium alloy powder is rolled into a green billet under an inert atmosphere to obtain a sheet or strip with a density of 3.85 g / cm³. 3 The green blank is stored in a vacuum environment after forming, and the time interval from the completion of forming to the start of sintering is 20 hours.

[0063] S300. The green blank is placed in a sintering furnace and sintered at 1100°C under vacuum, and held for 3 hours.

[0064] S400. After the vacuum sintering step, high-purity argon gas with a purity of 99.99% is introduced into the sintering furnace to maintain the pressure at 20MPa and continue to be held at 1100℃ for 2 hours.

[0065] The properties of the product obtained in this embodiment are as follows: the product density is 4.46 g / cm³.3 The porosity is 0.04%; the oxygen content is 2600 ppm; the tensile strength is 1100 MPa, the yield strength is 920 MPa, and the elongation is 12%.

[0066] Example 5 A low-oxygen, fully dense titanium alloy powder metallurgy method includes the following steps: S100. Provide titanium alloy powder, which includes two types of TB6 titanium alloy powder with different particle sizes: fine powder with a particle size of 0-25μm, an oxygen content of 1600ppm, a nitrogen content of 300ppm, and a hydrogen content of 200ppm; and coarse powder with a particle size of 50-100μm, an oxygen content of 1100ppm, a nitrogen content of 250ppm, and a hydrogen content of 180ppm. The fine powder and coarse powder are mixed at a weight ratio of 7:3. The oxygen, nitrogen, and hydrogen contents of the titanium alloy powder satisfy the relationship: O + 2N + 3H = 2400, and O / (N + H) = 4.5. Before forming, the titanium alloy powder is preheated at 400℃ under vacuum for 0.5 hours, then cooled to 30℃ under vacuum, and immediately subjected to forming.

[0067] S200. The mixed titanium alloy powder is cold isostatically pressed under an inert atmosphere to obtain a green billet, which is a solid bar with a density of 3.3 g / cm³. 3 The green blank is stored in an inert gas protective environment after forming, and the time interval from the completion of forming to the start of sintering is 18 hours.

[0068] S300. The green blank is placed in a sintering furnace and sintered at 1300°C under vacuum, and held at that temperature for 1 hour.

[0069] S400. After the vacuum sintering step, high-purity argon gas with a purity of 99.99% is introduced into the sintering furnace to maintain the pressure at 2MPa and continue to be held at 1300℃ for 4 hours.

[0070] The properties of the product obtained in this embodiment are as follows: the product density is 4.44 g / cm³. 3 The porosity is 0.09%; the oxygen content is 2950 ppm; the tensile strength is 980 MPa, the yield strength is 880 MPa, and the elongation is 14%.

[0071] Comparative Example 1 A titanium alloy powder metallurgy method, similar to Example 1, but without the pressure sintering step (i.e., S400 is omitted). Specific steps include: S100. Provide titanium alloy powder, wherein the titanium alloy powder is TC4 titanium alloy powder, with an oxygen content of 1500ppm, a nitrogen content of 200ppm, a hydrogen content of 150ppm, and a powder particle size ≤108μm.

[0072] S200. The titanium alloy powder is cold isostatically pressed under an inert atmosphere to obtain a green billet, which is a solid bar with a density of 3.4 g / cm³. 3 .

[0073] S300. The green blank is placed in a sintering furnace and sintered at 1150°C under vacuum, and held for 2 hours.

[0074] The properties of the product obtained in this comparative example are as follows: product density is 4.35 g / cm³. 3 The porosity is 1.5%; the oxygen content is 3200 ppm; the tensile strength is 850 MPa, the yield strength is 750 MPa, and the elongation is 8%.

[0075] Comparative Example 2 A titanium alloy powder metallurgy method, similar to Example 1, but the oxygen, nitrogen, and hydrogen content of the titanium alloy powder does not satisfy the relationship O / (N+H)≤5. Specific steps include: S100. Provide titanium alloy powder, wherein the titanium alloy powder is TC4 titanium alloy powder, with an oxygen content of 1800ppm, a nitrogen content of 100ppm, a hydrogen content of 100ppm (calculated as O / (N+H)=1800 / 200=9), and a powder particle size ≤108μm.

[0076] S200. The titanium alloy powder is cold isostatically pressed under an inert atmosphere to obtain a green billet, which is a solid bar with a density of 3.4 g / cm³. 3 .

[0077] S300. The green blank is placed in a sintering furnace and sintered at 1150°C under vacuum, and held for 2 hours.

[0078] S400. After the vacuum sintering step, high-purity argon gas with a purity of 99.99% is introduced into the sintering furnace to maintain the pressure at 5MPa and continue to be held at 1150°C for 3 hours.

[0079] The properties of the product obtained in this comparative example are as follows: product density is 4.38 g / cm³. 3 The porosity is 0.5%; the oxygen content is 3500 ppm; the tensile strength is 880 MPa, the yield strength is 780 MPa, and the elongation is 9%.

[0080] Comparative Example 3 A titanium alloy powder metallurgy method, similar to Example 1, but the oxygen, nitrogen, and hydrogen content of the titanium alloy powder does not satisfy the relationship O+2N+3H≤2500. Specific steps include: S100. Provide titanium alloy powder, wherein the titanium alloy powder is TC4 titanium alloy powder, with an oxygen content of 1800ppm, a nitrogen content of 400ppm, a hydrogen content of 200ppm (calculated as O+2N+3H=1800+800+600=3200>2500), and a powder particle size ≤108μm.

[0081] S200. The titanium alloy powder is cold isostatically pressed under an inert atmosphere to obtain a green billet, which is a solid bar with a density of 3.4 g / cm³. 3 .

[0082] S300. The green blank is placed in a sintering furnace and sintered at 1150°C under vacuum, and held for 2 hours.

[0083] S400. After the vacuum sintering step, high-purity argon gas with a purity of 99.99% is introduced into the sintering furnace to maintain the pressure at 5MPa and continue to be held at 1150°C for 3 hours.

[0084] The properties of the product obtained in this comparative example are as follows: product density is 4.36 g / cm³. 3 The porosity is 0.8%; the oxygen content is 3800 ppm; the tensile strength is 860 MPa, the yield strength is 760 MPa, and the elongation is 7%.

[0085] The above embodiments and comparative examples demonstrate that the present invention, through the combination of vacuum sintering and pressure sintering, and by controlling raw materials and process parameters, can achieve low-oxygen, fully densified titanium alloy products with excellent mechanical properties. In contrast, the comparative examples, due to the lack of a pressure step or improper control of interstitial elements, resulted in decreased product density and performance.

[0086] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A low oxygen fully dense titanium alloy powder metallurgy process characterized by, The method comprises the following steps: S100, providing a titanium alloy powder, the titanium alloy powder having an oxygen content of ≤1800 ppm, a nitrogen content of ≤300 ppm, and a hydrogen content of ≤200 ppm; S200, performing a forming treatment on the titanium alloy powder in an inert atmosphere or a vacuum environment to obtain a green body; S300, placing the green body in a sintering furnace, performing sintering on the green body in a vacuum environment at a temperature ranging from 1100 DEG C to 1300 DEG C, and maintaining the temperature for 1-3 hours; S400, after the vacuum sintering step, introducing an inert gas into the sintering furnace, maintaining the pressure at 2-20 MPa, and continuing to maintain the temperature at a range from 1100 DEG C to 1300 DEG C for 2-4 hours.

2. The low oxygen, fully dense titanium alloy powder metallurgy process of claim 1, wherein, In step S100, the titanium alloy powder is at least one of TC4, TA0, TA1, TA2, TC11, and TB6 titanium alloy powder, and the powder particle size is ≤108 μm.

3. The low oxygen fully dense titanium alloy powder metallurgy process of claim 2, wherein, The titanium alloy powder comprises at least two powders with different particle sizes, i.e., fine powder with a particle size of 0-25 μm and coarse powder with a particle size of 50-100 μm, and the fine powder and the coarse powder are mixed at a weight ratio of 2:8-8:

2.

4. The low oxygen, fully dense titanium alloy powder metallurgy process of claim 1, wherein, In step S200, the forming process is cold isostatic pressing, and the green compact is a solid rod having a density of 3.2 to 3.6 g / cm 3 .

5. The low oxygen, fully dense titanium alloy powder metallurgy process of claim 1, wherein, In step S200, the forming process is roll forming, and the green compact is a strip, with a density of 3.8-4.0 g / cm 3 .

6. The low oxygen, fully dense titanium alloy powder metallurgy process of claim 2, wherein, In step S400, the inert gas is high-purity argon or high-purity helium, and the purity is not less than 99.99%.

7. The low oxygen, fully dense titanium alloy powder metallurgy process of claim 3, wherein, In step S200, the green body must be stored in a vacuum or inert gas protection environment after forming, and the time interval from the completion of forming to the start of sintering in step S300 is not more than 24 hours.

8. The low oxygen, fully dense titanium alloy powder metallurgy process of claim 1, wherein, In step S100, the oxygen content (O), the nitrogen content (N), and the hydrogen content (H) of the titanium alloy powder satisfy the following relationship: O+2N+3H≤2500, and 2≤[O / (N+H)]≤5, and the units in the formula are ppm.

9. The low oxygen, fully dense titanium alloy powder metallurgy process of claim 8, wherein, The titanium alloy powder is preheated at 200 to 400°C under a vacuum degree of not higher than 1 x 10 -2 Pa for 0.5 to 2 hours, and then cooled to 50°C or lower under a vacuum environment, and immediately subjected to a forming process.

10. A low oxygen, fully dense titanium alloy, characterized in that, Articles with density ≥ 4.42 g / cm3, porosity ≤ 0.1 %, and oxygen content ≤ 3000 ppm, processed using the low-oxygen fully-dense titanium alloy powder metallurgy method of any of claims 1-9. 3 ; porosity ≤ 0.1 %; oxygen content ≤ 3000 ppm.