Titanium alloy powder for injection molding, injection molded titanium alloy article, and method of making

Abstract

The application belongs to the technical field of powder metallurgy and particularly relates to a titanium alloy powder for injection molding, an injection-molded titanium alloy part and a preparation method thereof. The titanium alloy powder for injection molding is obtained by shaping and surface energizing irregularly shaped hydrogenated dehydrogenated titanium alloy powder through a high-speed airflow impact particle composite shaping system. A nanoscale high-dislocation-density substructure layer is formed on the surface of the titanium alloy powder, and the sphericity of the titanium alloy powder is 0.7-0.8. The titanium alloy powder for injection molding is obtained by shaping and surface energizing low-cost irregularly shaped hydrogenated dehydrogenated titanium alloy powder through a high-speed airflow impact particle composite shaping system. Thus, low-cost, high-fluidity, high-tapping-density, high-sintering-energizing near-spherical titanium alloy powder for injection molding is obtained, and a nanoscale high-dislocation-density substructure layer is formed on the surface of the titanium alloy powder, thereby realizing sintering energization of high-sintering-driving-force powder.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, and specifically relates to a titanium alloy powder for injection molding, an injection-molded titanium alloy part, and a method for preparing the same. Background Technology

[0002] Titanium alloys are widely used in aerospace, defense, biomedicine, and consumer electronics due to their high specific strength, excellent biocompatibility, corrosion resistance, and thermal stability. In recent years, the miniaturization and lightweighting of consumer electronics components have continuously driven the demand for high-strength titanium alloys. Metal injection molding (MIM) technology can directly mass-produce three-dimensional complex-shaped parts, avoiding or reducing machining processes. With a material utilization rate approaching 100%, it is a resource-saving and energy-efficient low-cost manufacturing technology that solves the problems of difficult forming of complex structures, low material utilization, and high production costs associated with traditional melting and forging methods.

[0003] However, the current bottleneck restricting the widespread adoption of MIM titanium alloys lies in the low yield, insufficient production capacity, and high price of micro-atomized spherical titanium alloy powders (particle size ≤25μm) with high specific surface area and high sintering activity. In contrast, hydrogenated dehydrogenated titanium alloy powders have a simpler preparation process and lower cost, but their irregular shape and relatively large particle size result in poor powder flowability, low feed loading, and insufficient sintering activity in the green body, easily leading to injection defects and residual sintering porosity, thus deteriorating the material's mechanical properties. Therefore, existing hydrogenated dehydrogenated titanium alloy powders are not suitable for the process requirements of injection molding.

[0004] Therefore, in view of the above shortcomings, this invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a titanium alloy powder for injection molding, an injection-molded titanium alloy part, and a method for preparing the same. The titanium alloy powder for injection molding provided by this invention is obtained by shaping and surface-enhancing low-cost, irregularly shaped hydrogenated and dehydrogenated titanium alloy powder through a high-speed airflow impact particle composite shaping system. This results in a low-cost, high-flowability, high-tap-density, and high-sintering-enhancing near-spherical titanium alloy powder for injection molding. Furthermore, a nanoscale high-dislocation-density substructure layer is formed on the surface of the titanium alloy powder, achieving sintering-enhancing of the powder with high sintering driving force.

[0006] The first aspect of this invention provides a titanium alloy powder for injection molding. The titanium alloy powder is obtained by shaping and surface-encapsulating irregularly shaped hydrogenated and dehydrogenated titanium alloy powder using a high-speed airflow impact particle composite shaping system. A nanoscale high dislocation density substructure layer is formed on the surface of the titanium alloy powder, with a thickness of 200 nm to 300 nm, originating from the base surface. Dislocations and Conical Surfaces<c+a> The titanium alloy powder has a sphericity of 0.7 to 0.8, which is formed by small-angle grain boundaries generated by dislocation entanglement.

[0007] In some embodiments, the titanium alloy powder has a particle size of 10 μm to 40 μm and an oxygen content of ≤1800 ppm.

[0008] In some embodiments, the titanium alloy powder includes at least one of TC4, TA15, TA18, and TC18 powders.

[0009] The second aspect of the present invention provides a method for preparing the titanium alloy powder for injection molding as described in the first aspect. The preparation method includes the following steps: adding irregularly shaped hydrogenated dehydrogenated titanium alloy powder that has been sieved and dried into a high-speed airflow impact particle composite shaping system for shaping and surface energy application; and sieving and collecting the shaped and surface-energy-applied hydrogenated dehydrogenated titanium alloy powder to obtain the titanium alloy powder for injection molding with the desired particle size.

[0010] In some embodiments, the rotational speed of the high-speed airflow impact particle composite shaping system is 5000 r / min to 7000 r / min, the processing time is 30 min to 50 min, and the airflow pressure is 0.3 MPa to 0.5 MPa.

[0011] In some embodiments, the particle size D50 of the irregularly shaped hydrogenated dehydrogenated titanium-based powder is 15 μm to 45 μm, and the oxygen content is ≤1700 ppm.

[0012] In some embodiments, the drying temperature of the irregularly shaped hydrogenated dehydrogenated titanium alloy powder is 110°C to 130°C, and the drying time is 1 hour to 3 hours.

[0013] The third aspect of this invention provides a method for preparing injection-molded titanium alloy parts, the method comprising the following steps: ball milling and mixing the titanium alloy powder for injection molding described in the first aspect or the titanium alloy powder for injection molding prepared by the method described in the second aspect with carbon particles to obtain a mixed powder; mixing the mixed powder with a binder in a required ratio and crushing it into granular feedstock; performing injection molding on the feedstock to obtain a green blank; and subjecting the green blank to oxalic acid-catalyzed degreasing and vacuum degreasing sintering, followed by furnace cooling to obtain a titanium alloy part.

[0014] In some embodiments, the carbon particles include at least one of carbon black or graphite.

[0015] In some embodiments, the mass percentage of the added carbon particles relative to the total mass of the carbon particles and titanium alloy powder is 0.2 wt.% to 0.6 wt.%.

[0016] In some embodiments, the ball milling process involves rotating for 15 minutes and pausing for 15 minutes, with a ball milling speed of 150 r / min to 250 r / min and a ball milling time of 3 h to 6 h.

[0017] In some embodiments, the ball-to-powder ratio in ball milling is 2 to 5:1.

[0018] In some embodiments, the diameter of the grinding balls in the ball milling process is 3 mm or 6 mm.

[0019] In some embodiments, grinding balls with a diameter of 3 mm account for 70% to 80% of the total weight of the grinding balls, and grinding balls with a diameter of 6 mm account for 20% to 30% of the total weight of the grinding balls.

[0020] In some embodiments, anhydrous ethanol is added during the ball milling and mixing process, and the mass percentage of the added anhydrous ethanol is 1 wt.% to 2 wt.% of the total mass of carbon particles and titanium alloy powder.

[0021] In some embodiments, the injection temperature of the injection molding is 165℃~195℃, the injection pressure is 80MPa~110MPa, the holding pressure is 90MPa~120MPa, the holding time is 1s~4s, the mold temperature is 90℃~110℃, and the injection speed is 30mm / s~50mm / s.

[0022] In some embodiments, the oxalic acid catalytic degreasing is carried out under a protective atmosphere, with a degreasing temperature of 110℃~135℃, an acid inlet rate of 1.0g / min~2.0g / min, and a degreasing time of 8h~13h.

[0023] In some embodiments, the vacuum degreasing sintering includes a thermal degreasing stage and a vacuum sintering stage. The thermal degreasing stage has a vacuum degree of 10 Pa to 30 Pa, a thermal degreasing temperature of 500°C to 650°C, a heating rate of 2°C / min to 4°C / min, and a degreasing time of 4 h to 8 h. The vacuum sintering stage has a vacuum degree of 10 Pa to 30 Pa. -3 Pa~10 -5 Pa, sintering temperature is 1100℃~1200℃, heating rate is 2℃ / min~5℃ / min, sintering time is 3h~7h.

[0024] In some embodiments, the adhesive comprises the following components by weight percentage: 82% polyoxymethylene, 8% high-density polyethylene, 5% ethylene-vinyl acetate copolymer and 5% stearic acid.

[0025] In some embodiments, the mixing is carried out under a protective atmosphere, with a mixing temperature of 160°C to 190°C, a mixing speed of 15 r / min to 45 r / min, and a mixing time of 1 h to 2 h.

[0026] The fourth aspect of the present invention provides a method for preparing injection-molded titanium alloy parts, the method further comprising subjecting the titanium alloy parts obtained by vacuum debinding and sintering to two-phase solution heat treatment and aging heat treatment in sequence.

[0027] In some embodiments, the two-phase solution heat treatment includes heating the titanium alloy part to 890°C to 940°C at a rate of 5°C / min to 10°C / min, holding it at that temperature for 0.5h to 1h, and then water cooling.

[0028] In some embodiments, the aging heat treatment includes heating the titanium alloy part to 400°C to 550°C at a rate of 5°C / min to 10°C / min, holding it at that temperature for 4 hours to 8 hours, and then air cooling.

[0029] The fifth aspect of this invention provides an injection-molded titanium alloy part, which is prepared based on the preparation method described in the third aspect; the microstructure of the titanium alloy part consists of 60% to 70% equiaxed α phase, intergranular β phase, and dispersed fine TiC reinforcing phase; the equivalent circle diameter of the equiaxed α phase is 15 μm to 25 μm, and the equivalent circle diameter of the TiC reinforcing phase is 3 μm to 5 μm; the density of the titanium alloy part is 99.0% to 99.6%.

[0030] The sixth aspect of this invention provides an injection-molded titanium alloy part, which is prepared based on the preparation method described in the fourth aspect. The microstructure of the titanium alloy part consists of 40% to 60% equiaxed α phase, island-like β phase, and dispersed fine TiC reinforcing phase. The island-like β phase is composed of precipitated nanoscale secondary α bundles arranged in parallel and cross-distributed structures, with a thickness of 50 nm to 100 nm. The equivalent circle diameter of the equiaxed α phase is 15 μm to 25 μm, and the equivalent circle diameter of the TiC reinforcing phase is 3 μm to 5 μm.

[0031] The beneficial effects of this invention are:

[0032] (1) This invention provides a low-cost, high-flowability, high-tap-density, and high-sintering-enabling near-spherical titanium alloy powder suitable for injection molding technology. The powder is made from irregularly shaped hydrogenated dehydrogenated titanium alloy powder. The powder is shaped and modified by high-frequency and high-speed impaction through PCS technology. At the same time, a nanoscale high dislocation density substructure layer is constructed on its surface to achieve sintering-enabling of the powder with high sintering driving force.

[0033] (2) This invention provides a method for preparing near-fully dense, fine equiaxed titanium alloy parts. A small amount of fine carbon particles are added to PCS-shaped titanium alloy powder, and near-fully dense sintering is achieved by combining the sintering-enabling powder with the exothermic reaction at the Ti-C in-situ interface. At the same time, fine equiaxed grains with uniform deformation capability are obtained by using dispersed micron-sized TiC particles to pin the grain boundaries.

[0034] (3) The present invention provides a high-strength and ductile MIM titanium alloy part, the microstructure of which consists of dispersed TiC particles (3μm~5μm), 40%~60% content of ductile and tough primary equiaxed α phase (15μm~30μm), island β phase (20μm~30μm) and the nanoscale secondary α bundles precipitated inside (secondary α thickness 50nm~100nm).

[0035] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1This is a SEM image of the Ti-6Al-4V alloy powder for injection molding obtained after processing by the PCS system in Example 1 of the present invention;

[0038] Figure 2 The image shows the microstructure of the Ti-6Al-4V alloy part obtained after solution treatment and aging in the two-phase region in Example 1 of this invention.

[0039] Figure 3 This is a micrograph of the Ti-6Al-4V alloy part obtained by oxalic acid catalytic degreasing and vacuum degreasing sintering in Example 1 of the present invention. Detailed Implementation

[0040] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0041] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0042] In the description of the embodiments of this invention, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this invention, "multiple" means two or more, unless otherwise explicitly defined.

[0043] 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 the invention. 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 and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0044] In the description of the embodiments of this invention, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0045] In the description of the embodiments of the present invention, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0046] The first aspect of this invention provides a titanium alloy powder for injection molding, combined with Figure 1 The titanium alloy powder is described as being obtained by shaping and surface-entraining irregularly shaped hydrogenated and dehydrogenated titanium alloy powder using a high-speed airflow impact particle composite shaping system. This results in the formation of a nanoscale high dislocation density substructure layer on the surface of the titanium alloy powder, with a thickness of 200 nm to 300 nm, originating from the base surface. Dislocations and Conical Surfaces<c+a> The titanium alloy powder has a sphericity of 0.7 to 0.8 due to the formation of small-angle grain boundaries caused by dislocation entanglement.

[0047] In embodiments of the present invention, the titanium alloy powder for injection molding utilizes low-cost, irregularly shaped hydrogenated and dehydrogenated titanium alloy powder. This powder is shaped and modified using PCS shaping technology, which grinds and cuts the irregular edges of the powder surface to make the particles tend to spheroidize, significantly improving the powder's flowability and tap density. Simultaneously, during high-frequency, high-speed impact, a nanoscale high-dislocation-density substructure layer is constructed on the powder surface, imparting a large amount of distortion energy. This provides sintering driving force during subsequent vacuum sintering, promoting densification and thus improving the problem of insufficient sintering activity caused by larger powder particle sizes. Furthermore, the distortion energy imparted by the high-dislocation-density substructure layer on the powder surface places it in a non-equilibrium state. This unstable surface provides nucleation regions for β-phase nucleation during sintering, allowing the β-phase to be dispersed in an island-like morphology among the powder particles. This coordinated uniform deformation of the matrix ensures the subsequent preservation of plasticity and toughness.

[0048] It is worth mentioning that the substructure layer thickness of the nanoscale high dislocation density substructure layer is 200nm to 300nm, consisting of a base surface. Dislocations and Conical Surfaces<c+a> The formation of small-angle grain boundaries generated by dislocation entanglement enables the sintering of powders with high sintering driving force.

[0049] In some embodiments, the titanium alloy powder has a particle size of 10 μm to 40 μm and an oxygen content of ≤1800 ppm.

[0050] For example, the particle size of the titanium alloy powder can be one of 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm or any value that meets the above range.

[0051] For example, the oxygen content of the titanium alloy powder can be one of 1800ppm, 1700ppm, 1600ppm, 1500ppm, 1400ppm, 1300ppm, 1200ppm, 1100ppm, 1000ppm, 900ppm, 800ppm, 700ppm, 600ppm, 500ppm, 400ppm, 300ppm, 200ppm, 100ppm or any value that meets the above range.

[0052] In some embodiments, the titanium alloy powder may be titanium alloy grade powders such as TC4 (Ti-6Al-4V), TA15 (Ti-6.5Al-2Zr-1Mo-1V), TA18 (Ti-3Al-2.5V), and TC18 (Ti-5Al-5Mo-5V-1Cr-1Fe).

[0053] The second aspect of this invention provides a method for preparing the titanium alloy powder for injection molding described in the first aspect. The key to this method is to add irregularly shaped hydrogenated and dehydrogenated titanium alloy powder, which has been sieved and dried, into a high-speed airflow impact particle composite shaping system for shaping and surface energy application; and to sieve and collect the shaped and surface-energy-applied hydrogenated and dehydrogenated titanium alloy powder to obtain the titanium alloy powder for injection molding with the desired particle size.

[0054] In this embodiment of the invention, the preparation method of titanium alloy powder for injection molding is carried out according to the following steps.

[0055] 1) Raw material preparation: Weigh out irregularly shaped hydrogenated dehydrogenated titanium alloy powder with appropriate particle size.

[0056] In some embodiments, the irregularly shaped hydrogenated dehydrogenated titanium alloy powder includes titanium alloy grade powders such as TC4, TA15, TA18, and TC18.

[0057] In some embodiments, the particle size D50 of the irregularly shaped hydrogenated dehydrogenated titanium alloy powder is 15μm to 45μm. If the particle size is too fine, it is easy to be carried away by the airflow and escape, making recycling difficult; if the particle size is too coarse, it is difficult to achieve effective acceleration and sufficient plastic deformation.

[0058] For example, the particle size D50 of the irregularly shaped hydrogenated dehydrogenated titanium-based powder can be one of 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or any value that satisfies the above range.

[0059] In some embodiments, the oxygen content of the irregularly shaped hydrogenated dehydrogenated titanium alloy powder is ≤1700ppm.

[0060] For example, the oxygen content of the irregularly shaped hydrogenated dehydrogenated titanium alloy powder can be one of 1700ppm, 1600ppm, 1500ppm, 1400ppm, 1300ppm, 1200ppm, 1100ppm, 1000ppm, 900ppm, 800ppm, 700ppm, 600ppm, 500ppm, 400ppm, 300ppm, 200ppm, 100ppm or any value that meets the above range.

[0061] 2) Powder pretreatment: The irregular hydrogenated dehydrogenated powder from step 1) is sieved and dried.

[0062] In some embodiments, the irregular hydrogenated dehydrogenated powder is subjected to vibratory sieving to remove extremely coarse or extremely fine particles with a particle size D50 greater than 75 μm and less than 5 μm.

[0063] In some embodiments, the irregular hydrogenated dehydrogenated powder after sieving is dried at a temperature of 110°C to 130°C for a holding time of 1 hour to 3 hours to fully remove adsorbed water from the powder surface and prevent the powder from clumping during high-speed airflow conveying.

[0064] For example, the drying temperature of the irregular hydrogenated dehydrogenated titanium alloy powder is one of 110°C, 120°C, and 130°C, or any value within the above range.

[0065] For example, the drying time of the irregular hydrogenated dehydrogenated titanium alloy powder is one of 1h, 2h, 3h or any value within the above range.

[0066] In some embodiments, the irregular hydrogenated dehydrogenated powder is vacuum dried in a vacuum drying oven.

[0067] 3) Powder shaping and surface or sintering: The irregular hydrogenated dehydrogenated titanium alloy powder described in step 2) is fed into the PCS system through the material inlet. The PCS system is started to shape and sinter the irregularly shaped hydrogenated dehydrogenated titanium alloy powder. After the program ends, the PCS system is turned off and the shaped and sintered titanium alloy powder is collected.

[0068] In some embodiments, the rotor speed of the PCS system is 5000 r / min to 7000 r / min, the processing time is 30 min to 50 min, and the airflow pressure is 0.3 MPa to 0.5 MPa. This ensures that the powder is fed into the accelerating nozzle at a stable and controllable rate for impact shaping. If the rotor speed and grinding or processing time are too low, the probability of powder collision decreases, resulting in insufficient powder shaping and inadequate sintering energy; conversely, if the rotor speed and grinding or processing time are too high, energy consumption increases and fine powder is easily produced.

[0069] For example, the rotor speed in the PCS system can be one of 5000 r / min, 5500 r / min, 6000 r / min, 6500 r / min, 7000 r / min or any value that meets the above range.

[0070] For example, the grinding or processing time of the PCS system can be one of 30 min, 35 min, 40 min, 45 min, 50 min or any value that meets the above range.

[0071] For example, the airflow pressure of the PCS system can be one of 0.3MPa, 0.4MPa, 0.5MPa or any value that meets the above range.

[0072] In some embodiments, powder shaping and surface enhancement of the PCS system are performed under an inert atmosphere, requiring the continuous introduction of an inert gas (such as high-purity argon) into the sealed PCS system to reduce the oxygen content in the system to below 10 ppm.

[0073] 4) Powder post-processing: The shaped and empowered titanium alloy powder obtained in step 3) is sieved according to the required particle size, and a small amount of agglomerates that may be formed due to cold welding are separated to obtain titanium alloy powder for injection molding.

[0074] In this embodiment of the invention, the obtained titanium alloy powder for injection molding has a particle size D50 of 10μm to 40μm, an oxygen content of ≤1800ppm, a sphericity of 0.7 to 0.8, good flowability, and the surface of the titanium alloy powder has a nanoscale high dislocation density substructure layer, which stores high distortion energy.

[0075] Currently, given the high strength requirements for titanium alloy parts in consumer electronics components, the strength of MIM titanium alloys can be improved by introducing reinforcing phase particles or by undergoing solution aging and toughening heat treatment. However, the "strength-plasticity inversion" problem limits their widespread application. Therefore, it is urgent to propose a method for preparing high-performance injection-molded titanium alloy parts based on the aforementioned titanium alloy powders used for injection molding. The aim is to achieve a high-strength and plasticity-sustaining microstructure while improving powder flowability, increasing feed loading, and enhancing the sintering activity of the preform, thereby breaking through the technical constraints of low-cost, high-performance MIM titanium alloys.

[0076] The third aspect of this invention provides a method for preparing injection-molded titanium alloy parts. The key aspect of this method is that the titanium alloy powder for injection molding described in the first aspect or the titanium alloy powder for injection molding prepared by the method described in the second aspect is ball-milled and mixed with carbon particles to obtain a mixed powder; the mixed powder is then mixed with a binder in a required ratio and crushed into granular feedstock; the feedstock is then injection-molded to obtain a green blank; and the green blank is subjected to oxalic acid-catalyzed degreasing and vacuum degreasing sintering, followed by furnace cooling to obtain the titanium alloy part.

[0077] In this embodiment of the invention, to significantly improve the mechanical properties of MIM titanium alloy parts, a small amount of fine carbon particles are uniformly added to the shaped titanium alloy powder using low-energy ball milling technology. The in-situ exothermic reaction at the Ti-C interface further promotes sintering densification to near-full densification, while the generated dispersed micron-sized TiC particles pin the grain boundaries to obtain a fine equiaxed grain structure with uniform deformation capability.

[0078] In the embodiments of the present invention, the preparation method of injection-molded titanium alloy parts is specifically carried out according to the following steps.

[0079] S1: Raw material powder preparation: Weigh titanium alloy powder and carbon particles for injection molding according to the component ratio.

[0080] In some embodiments, the carbon particles include at least one of carbon black or graphite. For example, the carbon particles include both carbon black and graphite.

[0081] In some embodiments, the mass percentage of carbon particles added is 0.2 wt.% to 0.6 wt.% of the total mass of carbon particles and titanium alloy powder for injection molding. Exemplarily, the mass percentage of carbon particles added can be one of 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, or any value satisfying the above range.

[0082] S2: Ball milling and powder mixing: Weigh a trace amount of anhydrous ethanol, add the anhydrous ethanol, injection molding titanium alloy powder, carbon particles and grinding balls to the ball milling jar, start the planetary ball mill, and ball mill the injection molding titanium alloy powder and carbon particles to mix. After the ball milling is completed, take out the grinding balls and mixed powder from the ball milling jar.

[0083] In some embodiments, anhydrous ethanol is added during the ball milling process to act as an anti-agglomeration, lubricant, and coolant, preventing cold welding.

[0084] In some embodiments, the mass percentage of anhydrous ethanol added is 1 wt.% to 2 wt.% of the total mass of carbon particles and titanium alloy powder for injection molding. Exemplarily, the mass percentage of anhydrous ethanol added can be one of 1 wt.%, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%, 1.6 wt.%, 1.7 wt.%, 1.8 wt.%, 1.9 wt.%, or 2 wt.%, or any value satisfying the above range.

[0085] In some embodiments, the ball-to-powder ratio during ball milling is 2 to 5:1.

[0086] In some embodiments, during the ball milling process, a ball milling mode of rotating for 15 minutes and pausing for 15 minutes is used in a cycle to prevent the tank temperature from getting too high, and the ball milling speed is 150 r / min to 250 r / min, and the ball milling time is 3 h to 6 h.

[0087] For example, the ball mill speed can be one of 150 r / min, 160 r / min, 170 r / min, 180 r / min, 190 r / min, 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min, 250 r / min or any value that satisfies the above range.

[0088] For example, the ball milling time can be one of 3h, 4h, 5h, 6h or any value that satisfies the above range.

[0089] In some embodiments, the diameter Φ of the grinding balls selected during the ball milling and powder mixing process is 3 mm or 6 mm.

[0090] In some embodiments, grinding balls with a diameter Φ of 3 mm account for 70% to 80% of the total weight of the grinding balls, and grinding balls with a diameter Φ of 6 mm account for 20% to 30% of the total weight of the grinding balls. The large-diameter grinding balls are mainly responsible for providing dispersed energy, while the small-diameter grinding balls fill the gaps and improve grinding efficiency.

[0091] For example, the weight of the grinding ball with a diameter Φ of 3mm accounts for one of the following: 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80% of the total weight of the grinding ball, or any value within the above range.

[0092] For example, the weight of the grinding ball with a diameter Φ of 6mm accounts for one of the following: 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% of the total weight of the grinding ball, or any value within the above range.

[0093] It is worth mentioning that in step S2, anhydrous ethanol, titanium alloy powder for injection molding, carbon particles and grinding balls are loaded and sealed in the glove box. High-purity argon (Ar≥99.999%) is filled into the grinding jar as a protective atmosphere, and the oxygen content is controlled at <10ppm. After sealing, the airtightness is confirmed to be good.

[0094] S3: Powder post-processing, using a sieve to separate the grinding balls from the mixed powder described in step S2, and removing residual anhydrous ethanol from the mixed powder by drying.

[0095] In some embodiments, the mixed powder is placed in a vacuum drying oven and dried at 60°C to 80°C for 2 to 4 hours to remove residual anhydrous ethanol.

[0096] For example, the drying temperature of the mixed powder can be one of 60°C, 65°C, 70°C, 75°C, 80°C or any value that meets the above range.

[0097] For example, the drying time of the mixed powder can be one of 2h, 3h, 4h or any value that meets the above range.

[0098] S4: Prepare the feed by mixing the mixed powder after step S3 with the binder in the required ratio and crushing it into granular feed.

[0099] In some embodiments, the adhesive comprises the following components by weight percentage: 82% polyoxymethylene, 8% high-density polyethylene, 5% ethylene-vinyl acetate copolymer and 5% stearic acid.

[0100] In some embodiments, the volume ratio of the adhesive is 40 vol.%.

[0101] In some embodiments, the mixing is carried out under a protective atmosphere, with a mixing temperature of 160°C to 190°C, a mixing speed of 15 r / min to 45 r / min, and a mixing time of 1 h to 2 h.

[0102] For example, the mixing temperature can be one of 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C or any value that satisfies the above range.

[0103] For example, the mixing speed can be one of 15 r / min, 20 r / min, 25 r / min, 30 r / min, 35 r / min, 40 r / min, or 45 r / min, or any value that satisfies the above range.

[0104] For example, the mixing time can be one of 1 hour, 2 hours, or any value that meets the above range.

[0105] In some embodiments, the protective atmosphere for mixing can be high-purity argon.

[0106] S5: Injection molding, the feed material from step S4 is injected into an injection molding machine to obtain a green preform.

[0107] In some embodiments, the injection temperature of injection molding is 165℃~195℃, the injection pressure is 80MPa~110MPa, the holding pressure is 90MPa~120MPa, the holding time is 1s~4s, the mold temperature is 90℃~110℃, and the injection speed is 30mm / s~50mm / s.

[0108] For example, the injection temperature for injection molding can be one of 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C or any value that meets the above range.

[0109] For example, the injection pressure for injection molding can be one of 80MPa, 85MPa, 90MPa, 95MPa, 100MPa, 105MPa, 110MPa or any value that meets the above range.

[0110] For example, the holding pressure during injection molding can be one of 90MPa, 95MPa, 100MPa, 105MPa, 110MPa, 115MPa, 120MPa or any value that meets the above range.

[0111] For example, the holding time for injection molding can be one of 1s, 2s, 3s, 4s or any value that meets the above range.

[0112] For example, the injection molding temperature can be one of 90°C, 95°C, 100°C, 105°C, 110°C or any value that meets the above range.

[0113] For example, the injection speed for injection molding can be one of 30 mm / s, 35 mm / s, 40 mm / s, 45 mm / s, 50 mm / s or any value that meets the above range.

[0114] S6: Catalytic degreasing, subjecting the green body obtained in step S5 to oxalic acid catalytic degreasing treatment.

[0115] In some embodiments, oxalic acid catalytic degreasing is carried out under a protective atmosphere, with a degreasing temperature of 110℃~135℃, an acid inlet rate of 1.0g / min~2.0g / min, and a degreasing time of 8h~13h.

[0116] For example, oxalic acid catalytic degreasing is performed under a protective atmosphere of high-purity nitrogen (N≥99.99%).

[0117] For example, the degreasing temperature for oxalic acid catalytic degreasing can be one of 110°C, 115°C, 120°C, 125°C, 130°C, or 135°C, or any value within the above range.

[0118] For example, the defatting time for oxalic acid catalytic defatting can be one of 8h, 9h, 10h, 11h, 12h, 13h or any value within the above range.

[0119] For example, the oxalic acid catalytic defatting rate can be one of 1.0 g / min, 1.1 g / min, 1.2 g / min, 1.3 g / min, 1.4 g / min, 1.5 g / min, 1.6 g / min, 1.7 g / min, 1.8 g / min, 1.9 g / min, 2.0 g / min or any value within the above range.

[0120] S7: Vacuum degreasing and sintering. The degreased blank obtained in step S6 is subjected to vacuum degreasing and sintering treatment, and then cooled in the furnace to obtain titanium alloy parts.

[0121] In some embodiments, vacuum degreasing sintering includes a hot degreasing stage and a vacuum sintering stage. The vacuum degree of the hot degreasing stage is 10 Pa to 30 Pa, the hot degreasing temperature is 500 °C to 650 °C, the heating rate is 2 °C / min to 4 °C / min, and the degreasing time is 4 h to 8 h.

[0122] For example, the heat degreasing temperature can be one of 500°C, 550°C, 600°C, 650°C or any value that meets the above range.

[0123] For example, the heating rate during the thermal degreasing stage can be one of 2℃ / min, 3℃ / min, 4℃ / min, or any value that meets the above range.

[0124] For example, the degreasing time during the heat degreasing stage can be one of 4h, 5h, 6h, 7h, 8h or any value within the range mentioned above.

[0125] For example, the vacuum level during the thermal degreasing stage can be one of 10 Pa, 15 Pa, 20 Pa, 25 Pa, or 30 Pa, or any value within the range mentioned above.

[0126] In some embodiments, the vacuum degree during the vacuum sintering stage is 10. -3 Pa~10 -5 Pa, sintering temperature is 1100℃~1200℃, heating rate is 2℃ / min~5℃ / min, sintering time is 3h~7h.

[0127] For example, the vacuum degree during the vacuum sintering stage can be 10. -3 10 -4 10 -5 One of Pa or any value that satisfies the above range.

[0128] For example, the temperature of the vacuum sintering stage can be one of 1100°C, 1150°C, 1200°C or any value that meets the above range.

[0129] For example, the heating rate during the vacuum sintering stage can be one of 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, or any value within the above range.

[0130] For example, the sintering time in the vacuum sintering stage can be one of 3h, 4h, 5h, 6h, 7h or any value that meets the above range.

[0131] A fourth aspect of this invention provides an injection-molded titanium alloy part, which is prepared based on the preparation method described in the third aspect; the microstructure of the titanium alloy part consists of 60% to 70% equiaxed α phase, intergranular β phase, and dispersed fine TiC reinforcing phase; the equivalent circle diameter of the equiaxed α phase is 15 μm to 25 μm, and the equivalent circle diameter of the TiC reinforcing phase is 3 μm to 5 μm; the density of the titanium alloy part is 99.0% to 99.6%.

[0132] The fifth aspect of the present invention also provides a method for preparing injection-molded titanium alloy parts, the key to which is to sequentially subject the titanium alloy parts prepared by the method described in the third aspect or the titanium alloy parts described in the fourth aspect to two-phase solution heat treatment and aging heat treatment.

[0133] In this embodiment of the invention, fine carbon particles are uniformly mixed into shaped titanium alloy powder using low-energy ball milling technology. Then, the powder is subjected to injection molding, catalytic degreasing, vacuum degreasing sintering, and solution aging heat treatment to obtain a MIM titanium alloy part with near-full density, fine equiaxed crystals, and high strength and plasticity.

[0134] In this embodiment of the invention, the preparation method of the injection-molded titanium alloy part is carried out according to the following steps.

[0135] S8: Heat treatment preparation. Place the injection-molded titanium alloy part obtained in step S7 on a zirconia firing plate and put it into a tube furnace.

[0136] In some embodiments, the zirconia sintering plate is placed in a drying oven and dried at 400°C to 600°C for 2 to 4 hours. After being removed, it is polished smooth with sandpaper. At the same time, high-purity argon gas is continuously introduced into the tube furnace tube to exhaust air.

[0137] For example, the drying temperature of the zirconia sintering plate can be one of 400°C, 450°C, 500°C, 550°C, 600°C or any value that meets the above range.

[0138] For example, the drying time of the zirconia sintering plate can be one of 2h, 3h, 4h or any value that meets the above range.

[0139] S9: Two-phase solution heat treatment, heating the injection-molded titanium alloy part to the two-phase solution temperature, holding it at that temperature, and then removing it for water cooling.

[0140] In some embodiments, the two-phase solution heat treatment includes heating the injection-molded titanium alloy part to 890°C to 940°C at a rate of 5°C / min to 10°C / min, holding it at that temperature for 0.5h to 1h, and then water cooling.

[0141] In order to further improve the tensile strength of the parts and retain the advantages of primary α phase content and fine grain structure in the sintered state, the solution treatment temperature is set to 890℃~940℃ in the two-phase region in this invention. By precisely controlling the solution temperature, the content of primary α phase with plasticity and toughness can be maintained, excessive grain coarsening can be suppressed, and as much metastable β phase and α′ martensite as possible can be obtained.

[0142] For example, the heating rate of the two-phase solution heat treatment can be one of 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min or any value that satisfies the above range.

[0143] For example, the solution temperature in the two-phase region can be one of 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, or any value within the range described above.

[0144] For example, the heat preservation time can be one of 0.5h, 1h, or any value that meets the above range.

[0145] S10: Aging heat treatment, heating the titanium alloy part described in step S9 to the aging temperature, holding it at that temperature, and then removing it for air cooling.

[0146] In some embodiments, the aging heat treatment includes heating the titanium alloy part to 400°C to 550°C at a rate of 5°C / min to 10°C / min, holding it at that temperature for 4 hours to 8 hours, and then air cooling.

[0147] After aging treatment at 400℃~550℃, such as 500℃, the microstructure consists of diffusely distributed TiC particles (3μm~5μm), 40%~60% equiaxed α phase (15μm~25μm), and nanoscale secondary α clusters precipitated in island-like β phases (secondary α thickness 50nm~100nm). During deformation, the diffusely distributed TiC particles hinder dislocation slip through the Orovan mechanism, resulting in localized stress concentration. A specific twinning critical shear stress triggers twin nucleation, shifting the dominance of dislocation slip to twinning-induced plasticity, significantly improving strength while coordinating plastic strain. Meanwhile, the numerous phase interfaces introduced by the nanoscale secondary α bundles precipitated in the β phase also hinder dislocation movement, which, combined with grain refinement, enhances the material's mechanical properties, ultimately achieving a high-strength, high-ductility, multi-scale microstructure.

[0148] For example, the heating rate of the aging heat treatment can be one of 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min or any value that satisfies the above range.

[0149] For example, the temperature of the aging heat treatment can be one of 400°C, 450°C, 500°C, 550°C or any value that meets the above range.

[0150] For example, the holding time for aging heat treatment can be one of 4h, 5h, 6h, 7h, 8h or any value within the above range.

[0151] In some embodiments, the method for preparing injection-molded titanium alloy parts includes:

[0152] (1) The irregularly shaped hydrogenated dehydrogenated titanium alloy powder after sieving and drying is shaped and sintered using PCS, and the obtained shaped and sintered titanium alloy powder is sieved and collected according to the required particle size to obtain titanium alloy powder for injection molding with a particle size of 10μm~40μm, oxygen content ≤1800ppm, and sphericity of 0.7~0.8; wherein, the process parameters of the PCS system include: rotor speed of 5000r / min~7000r / min, processing time of 30min~50min, and air pressure of 0.3MPa~0.5MPa.

[0153] (2) Weigh the titanium alloy powder, carbon particles, and anhydrous ethanol for injection molding according to the component ratio, add the three components and grinding balls to a ball mill jar, and ball mill the titanium alloy powder and carbon particles to mix them. Then, use a sieve to separate the grinding balls from the mixed powder, and remove the residual anhydrous ethanol from the mixed powder by drying. The ball milling process parameters include: ball milling speed of 150 r / min to 250 r / min, time of 3 h to 6 h, and a cycle of 15 min rotation followed by 15 min pause.

[0154] (3) The mixed powder and binder are mixed in the required proportion, crushed into granules, and then injected into a green body on an injection molding machine. The mixing process parameters include: mixing temperature of 160℃~190℃, rotation speed of 15r / min~45r / min, and time of 1h~2h; the injection molding process parameters include: injection temperature of 165℃~195℃, injection pressure of 80MPa~110MPa, holding pressure of 90MPa~120MPa, holding time of 1s~4s, mold temperature of 90℃~110℃, and injection speed of 30mm / s~50mm / s.

[0155] (4) The injection-molded green compact was subjected to oxalic acid catalytic degreasing and vacuum degreasing sintering, and then cooled in the furnace to obtain titanium alloy parts. The catalytic degreasing process parameters included: degreasing temperature of 110℃~135℃, acid injection rate of 1.0g / min~2.0g / min, and degreasing time of 8h~13h; the vacuum degreasing sintering process parameters included: hot degreasing temperature of 500℃~650℃, heating rate of 2℃ / min~4℃ / min, and degreasing time of 4h~8h; and vacuum sintering temperature of 1100℃~1200℃, heating rate of 2℃ / min~5℃ / min, and sintering time of 3h~7h. After cooling in the furnace, near-fully dense fine equiaxed equiaxed MIM titanium alloy parts were obtained.

[0156] (5) Place the zirconia sintering plate in a drying oven and dry it at 400℃~600℃ for 2h~4h. After removing it, polish it smooth with sandpaper. Place the MIM titanium alloy part on the zirconia sintering plate and put it into a tube furnace. Heat the titanium alloy part to the two-phase region, hold it at that temperature, and then water cool it. Then heat it to the aging temperature and air cool it. The heat treatment process parameters include: solution treatment, heating at 5℃ / min~10℃ / min to the two-phase region temperature of 890℃~940℃, holding it at that temperature for 0.5h~1h, and then removing it and water cooling it; aging treatment, heating at 5℃ / min~10℃ / min to 400℃~550℃, holding it at that temperature for 4h~8h, and then removing it and air cooling it to obtain a high-strength and high-ductility MIM titanium alloy part.

[0157] The sixth aspect of this invention provides an injection-molded titanium alloy part, the key being that the titanium alloy part is prepared based on the preparation method described in the fifth aspect. The titanium alloy part prepared by solution aging with microstructure control in the dual-phase region retains the ductile and tough morphology of a high proportion of primary α phase and uniformly distributed β phase, and has near-fully dense and fine-grained characteristics. The microstructure of the titanium alloy part consists of 40% to 60% equiaxed α phase, island-like β phase, and dispersed fine TiC reinforcing phase. The island-like β phase is composed of precipitated nanoscale secondary α bundles arranged in parallel and cross-distributed structures, with a thickness of 50 nm to 100 nm. The equivalent circle diameter of the equiaxed α phase is 15 μm to 25 μm, and the equivalent circle diameter of the TiC reinforcing phase is 3 μm to 5 μm.

[0158] In some embodiments, the multi-scale microstructure of titanium alloy parts provides high tensile strength and high plasticity retention.

[0159] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or through existing methods; unless otherwise specified, the amounts of experimental reagents used are the amounts used in conventional experimental operations; unless otherwise specified, the experimental methods are conventional methods. It should be further noted that the following descriptions are merely exemplary and not intended to limit the specific scope of the invention. Moreover, the comparative examples below are selected to compare with the technical solutions of the present invention to demonstrate the advancement of the present invention, and do not necessarily represent prior art in this technical field.

[0160] Example 1

[0161] Irregularly shaped hydrogenated dehydrogenated Ti-6Al-4V titanium alloy powder with a particle size D50 of 15μm to 45μm and an oxygen content ≤1700ppm was weighed and subjected to vibratory sieving to remove extremely coarse or fine particles. The powder was then vacuum dried at 120℃ for 2 hours in a vacuum drying oven. The dried powder was then fed into a PCS system through the material inlet for powder shaping and sintering. The PCS system rotor speed was 6000 r / min, the grinding time was 40 min, and the airflow pressure was 0.4 MPa. The shaped and energized Ti-6Al-4V titanium alloy powder was sieved according to the desired particle size to obtain Ti-6Al-4V titanium alloy powder for injection molding with a particle size D50 of 10μm to 40μm, an oxygen content ≤1800ppm, a sphericity of 0.7 to 0.8, and good flowability. This powder possesses a high sintering driving force substructure layer with a thickness of 200nm to 300nm, originating from the basal surface. Dislocations and Conical Surfaces<c+a> Small-angle grain boundaries are formed by dislocation entanglement.

[0162] Carbon black particles with a particle size of 1μm to 3μm were weighed, and the weight was calculated as 0.4 wt.% of the total mass of carbon black particles and titanium alloy powder for injection molding. Simultaneously, anhydrous ethanol was weighed as 1 wt.% of the total mass of carbon black particles and titanium alloy powder for injection molding. The anhydrous ethanol, titanium alloy powder, carbon black particles, and grinding balls were added to the grinding jar. The ball-to-powder ratio (grinding balls: a mixture of titanium alloy powder and carbon black particles) was 4:1, with 70% by weight of Φ3mm grinding balls and 30% by weight of Φ6mm grinding balls. The grinding jar was loaded and sealed in a glove box, and high-purity argon was introduced into the jar as a protective atmosphere. Start the planetary ball mill, set the milling speed to 200 r / min, and the milling time to 4 h, cycling the mill in a 15 min rotation, 15 min pause pattern to mix the shaped and sintered energized titanium alloy powder and carbon black particles. After the program ends, remove the grinding balls and mixed powder from the mill jar. Separate the grinding balls and mixed powder using a sieve, and place the mixed powder in a vacuum drying oven at 80 °C for 4 h to remove residual anhydrous ethanol.

[0163] The mixed powder and binder (polyoxymethylene, high-density polyethylene, ethylene-vinyl acetate copolymer and stearic acid) were mixed in a high-purity argon atmosphere at a mass ratio of mixed powder:polyoxymethylene:high-density polyethylene:ethylene-vinyl acetate copolymer:stearic acid of 82:8:5:5. The mixing temperature was 180℃, the speed was 35r / min, and the time was 1h. The mixture was then crushed into granular feed.

[0164] The granular feedstock was injected into a green body on an injection molding machine at an injection temperature of 185℃, an injection pressure of 100MPa, a holding pressure of 110MPa, a holding time of 2s, a mold temperature of 95℃, and an injection speed of 35mm / s.

[0165] The injection-molded green body was subjected to oxalic acid catalytic degreasing treatment with high-purity nitrogen as the protective atmosphere. The degreasing temperature was 130℃, the acid injection rate was 1.5g / min, and the degreasing time was 10h.

[0166] The degreased green body was subjected to vacuum degreasing and sintering treatment. The vacuum degree during the hot degreasing stage was 20 Pa, the hot degreasing temperature was 550℃, the heating rate was 3℃ / min, and the degreasing time was 6 h. The vacuum degree during the sintering stage was 10 Pa. -4 The vacuum sintering temperature was 1150℃, the heating rate was 2℃ / min, and the sintering time was 4h. After furnace cooling, a nearly fully dense, fine-grained equiaxed equiaxed MIM titanium alloy part was obtained. The microstructure of the titanium alloy part consists of 65% equiaxed α phase, intergranular β phase, and dispersed fine TiC reinforcing phase; the equivalent circle diameter of the equiaxed α phase is 20μm, and the equivalent circle diameter of the TiC reinforcing phase is 4μm; the density of the titanium alloy part is 99.5%.

[0167] The MIM titanium alloy part was placed on a zirconia sintering plate and then placed in a tube furnace. High-purity argon gas was continuously introduced into the furnace tubes, while air was vented out. Two-phase solution and aging heat treatments were performed. The solution heat treatment involved heating to 910℃ at a rate of 5℃ / min and holding for 0.5h, followed by water cooling. The aging heat treatment involved heating to 450℃ at a rate of 5℃ / min and holding for 5h, followed by air cooling. This yielded a titanium alloy part prepared by solution aging with controlled microstructure in the two-phase region.

[0168] The Ti-6Al-4V titanium alloy parts finally obtained in Example 1 were subjected to the following performance tests, and the test results are recorded in Table 1.

[0169] Performance testing

[0170] (1) Density test: The density of titanium alloy parts was determined using the Archimedes displacement method.

[0171] (2) Mechanical property testing.

[0172] Mechanical property testing was conducted in accordance with GB / T 228.1-2021, and the test samples were M6 standard tensile specimens.

[0173] Table 1

[0174]

[0175] Examples 2-4

[0176] Except for the powder material, type and content of carbon particles, vacuum sintering temperature and solution heat treatment temperature as shown in Table 2, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0177] Table 2

[0178]

[0179] Testing revealed that the MIM titanium alloy parts prepared in Examples 1-4 of this invention were all nearly fully dense (>99.0%), composed of dispersed TiC particles, 40%–60% content of primary equiaxed α phase with high plasticity and toughness, island-like β phase, and nanoscale secondary α bundles precipitated within them. This represents a high-strength, high-ductility, multi-scale microstructure controlled by microstructure. Specifically, the island-like β phase is composed of precipitated nanoscale secondary α bundles arranged in parallel and intersecting patterns, with a thickness of 50 nm–100 nm. The equivalent circle diameter of the equiaxed α phase is 15 μm–25 μm, and the equivalent circle diameter of the TiC reinforcing phase is 3 μm–5 μm.

[0180] Comparative Example 1

[0181] Except that the powder raw material used for injection molding was atomized spherical Ti-6Al-4V powder of the same particle size, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0182] Comparative Example 2

[0183] Except that the rotor speed was 9000 r / min during the PCS system processing, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0184] Comparative Example 3

[0185] Except for the PCS system processing time of 60 minutes, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0186] Comparative Example 4

[0187] Except for the addition of 1.0 wt.% of carbon black, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0188] Comparative Example 5

[0189] Except for the vacuum sintering temperature of 1000℃, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0190] Comparative Example 6

[0191] Except for the solution temperature of 960°C, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0192] Comparative Example 7

[0193] Except for the solution time of 2 hours, the preparation and testing were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0194] Combination Figures 1-3 As shown in Table 1, Comparative Example 1 uses atomized spherical Ti-6Al-4V powder of the same particle size as raw material. Due to its low specific surface energy, the sintering activity is insufficient. At the same time, the powder surface is not distorted and a high dislocation density substructure layer at the nanoscale is not constructed. The lack of high distortion energy makes it difficult to densify during the sintering process, resulting in a low-density microstructure. The microstructure is 98.3% dense and consists of dispersed TiC particles, 40% to 60% content of ductile and tough primary equiaxed α phase, island β phase and nanoscale secondary α bundles precipitated inside. Uneven strain at the residual pores leads to severe stress concentration, crack initiation and rapid propagation, and greatly reduces strength and plasticity.

[0195] In Comparative Examples 2 and 3, the PCS shaping rotor speed and shaping time were increased. Excessive shaping increases the amount of fine powder, which adheres to the surface of large powder particles and agglomerates, thus reducing its flowability. As a result, the injection defect rate during injection molding increases significantly, and the sintered parts have more cracks and pores, which greatly reduces their mechanical properties.

[0196] The excessive addition of carbon black in Comparative Example 4 led to a decrease in the uniformity of carbon black particle distribution after ball milling and mixing, resulting in local segregation and a significant deterioration of plasticity. The reduction in vacuum sintering temperature in Comparative Example 5 resulted in insufficient Ti-C reaction, leaving many incompletely closed pore defects in the final sintered state, which significantly deteriorated the plasticity.

[0197] In Comparative Examples 6 and 7, the excessively high solution heat treatment temperature and prolonged holding time significantly reduced the content of the primary α phase in the microstructure and caused coarsening, resulting in a decrease in the uniform deformation capacity of the matrix. At the same time, the large number of nanoscale secondary α bundles precipitated in the β phase introduced excessive phase interfaces, hindering dislocation movement, causing the multi-scale microstructure to lose its ability to coordinate strain, and significantly reducing plasticity.

[0198] In summary, it can be seen that any change in raw materials or process parameters in this invention will directly affect the densification mechanism and microstructure evolution of the parts. As a result, it is impossible to obtain a near-fully dense, high-strength, high-ductility multi-scale microstructure of titanium alloy parts containing dispersed TiC particles, high content of ductile and tough primary equiaxed α phase, island-like β phase and nanoscale secondary α bundles precipitated inside, which leads to the inability to effectively improve the strength and ductility of the final parts.

[0199] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A titanium alloy powder for injection molding, characterized in that, The titanium alloy powder for injection molding is obtained by shaping and surface-encapsulating irregularly shaped hydrogenated and dehydrogenated titanium alloy powder using a high-speed airflow impact particle composite shaping system. The high-speed airflow impact particle composite shaping system has a rotation speed of 5000 r / min to 7000 r / min, a processing time of 30 min to 50 min, and an airflow pressure of 0.3 MPa to 0.5 MPa. The surface of the titanium alloy powder used for injection molding forms a nanoscale high dislocation density substructure layer with a thickness of 200 nm to 300 nm, which is formed by the base surface. Dislocations and Conical Surfaces<c+a> The small-angle grain boundaries formed by dislocation entanglement result in a sphericity of 0.7~0.8 for the titanium alloy powder used in injection molding.

2. The titanium alloy powder for injection molding as described in claim 1, characterized in that, The titanium alloy powder used for injection molding has a particle size of 10 μm to 40 μm and an oxygen content of ≤1800 ppm.

3. The titanium alloy powder for injection molding as described in claim 1, characterized in that, The titanium alloy powder for injection molding includes at least one of TC4, TA15, TA18, and TC18 powders.

4. A method for preparing titanium alloy powder for injection molding according to any one of claims 1 to 3, characterized in that, The preparation method includes the following steps: Irregularly shaped hydrogenated dehydrogenated titanium alloy powder, after sieving and drying, is added to a high-speed airflow impact particle composite shaping system for shaping and surface energy application. The high-speed airflow impact particle composite shaping system has a rotation speed of 5000 r / min to 7000 r / min, a processing time of 30 min to 50 min, and an airflow pressure of 0.3 MPa to 0.5 MPa. as well as The hydrogenated and dehydrogenated titanium alloy powder that has been shaped and surface-energized is sieved and collected to obtain the titanium alloy powder for injection molding with the required particle size.

5. The preparation method according to claim 4, characterized in that, The irregularly shaped hydrogenated dehydrogenated titanium alloy powder has a particle size D50 of 15 μm to 45 μm and an oxygen content ≤1700 ppm.

6. The preparation method according to claim 4, characterized in that, The drying temperature of the irregularly shaped hydrogenated dehydrogenated titanium alloy powder is 110 ℃~130 ℃, and the drying time is 1 h~3 h.

7. A method for preparing an injection-molded titanium alloy part, characterized in that, Includes the following steps: The titanium alloy powder for injection molding according to any one of claims 1 to 3 or the titanium alloy powder for injection molding prepared by any one of claims 4 to 6 is ball-milled with carbon particles to obtain a mixed powder. The mixed powder and binder are mixed in the required proportions and then crushed into granular feed. The feed is injection molded to obtain a green body; and The green blank is subjected to oxalic acid-catalyzed degreasing and vacuum degreasing sintering, and then cooled in the furnace to obtain injection-molded titanium alloy parts.

8. The preparation method according to claim 7, characterized in that, The carbon particles include at least one of carbon black or graphite.

9. The preparation method according to claim 7, characterized in that, The mass percentage of the added carbon particles to the total mass of the carbon particles and the titanium alloy powder for injection molding is 0.2 wt.% to 0.6 wt.%.

10. The preparation method according to claim 7, characterized in that, In the ball milling process, a ball milling mode of rotating for 15 minutes and pausing for 15 minutes was adopted. The ball milling speed was 150 r / min to 250 r / min, and the ball milling time was 3 h to 6 h.

11. The preparation method according to claim 7, characterized in that, In ball milling and powder mixing, the ball-to-material ratio is 2~5:

1.

12. The preparation method according to claim 7, characterized in that, In the ball milling process, the diameters of the grinding balls are 3 mm and 6 mm.

13. The preparation method according to claim 12, characterized in that, Grinding balls with a diameter of 3 mm account for 70% to 80% of the total weight of the grinding balls, while grinding balls with a diameter of 6 mm account for 20% to 30% of the total weight of the grinding balls.

14. The preparation method according to claim 7, characterized in that, Anhydrous ethanol is added during the ball milling and mixing process, and the mass percentage of the added anhydrous ethanol is 1 wt.% to 2 wt.% of the total mass of carbon particles and titanium alloy powder for injection molding.

15. The preparation method according to claim 7, characterized in that, The injection molding process involves an injection temperature of 165 ℃ to 195 ℃, an injection pressure of 80 MPa to 110 MPa, a holding pressure of 90 MPa to 120 MPa, a holding time of 1 s to 4 s, a mold temperature of 90 ℃ to 110 ℃, and an injection speed of 30 mm / s to 50 mm / s.

16. The preparation method according to claim 7, characterized in that, The oxalic acid-catalyzed degreasing was carried out under a protective atmosphere, with a degreasing temperature of 110 ℃ to 135 ℃, an acid inlet rate of 1.0 g / min to 2.0 g / min, and a degreasing time of 8 h to 13 h.

17. The preparation method according to claim 7, characterized in that, The vacuum degreasing sintering includes a thermal degreasing stage and a vacuum sintering stage. The thermal degreasing stage has a vacuum degree of 10 Pa to 30 Pa, a thermal degreasing temperature of 500 ℃ to 650 ℃, a heating rate of 2 ℃ / min to 4 ℃ / min, and a degreasing time of 4 h to 8 h. The vacuum sintering stage has a vacuum degree of 10 Pa to 30 Pa. -3 Pa~10 -5 Pa, sintering temperature is 1100 ℃~1200 ℃, heating rate is 2 ℃ / min~5 ℃ / min, sintering time is 3 h~7 h.

18. The preparation method according to claim 7, characterized in that, The adhesive comprises the following components by weight percentage: 82% polyoxymethylene, 8% high-density polyethylene, 5% ethylene-vinyl acetate copolymer and 5% stearic acid.

19. The preparation method according to claim 7, characterized in that, The mixing is carried out under a protective atmosphere, with a mixing temperature of 160 ℃ to 190 ℃, a mixing speed of 15 r / min to 45 r / min, and a mixing time of 1 h to 2 h.

20. The preparation method according to any one of claims 7 to 19, characterized in that, The preparation method further includes: The injection-molded titanium alloy parts obtained by vacuum degreasing and sintering are subjected to two-phase solution heat treatment and aging heat treatment in sequence.

21. The preparation method according to claim 20, characterized in that, The two-phase solution heat treatment includes heating the titanium alloy part to 890 ℃ to 940 ℃ at a rate of 5 ℃ / min to 10 ℃ / min, holding it at that temperature for 0.5 h to 1 h, and then water cooling it.

22. The preparation method according to claim 20, characterized in that, The aging heat treatment includes heating the titanium alloy part to 400 ℃~550 ℃ at a rate of 5 ℃ / min~10 ℃ / min, holding it at that temperature for 4 h~8 h, and then air cooling.

23. An injection-molded titanium alloy part, characterized in that, The injection-molded titanium alloy part is prepared based on the preparation method according to any one of claims 7 to 19; The microstructure of the injection-molded titanium alloy part consists of 60%~70% equiaxed α phase, intergranular β phase, and dispersed fine TiC reinforcing phase; the equivalent circle diameter of the equiaxed α phase is 15 μm~25 μm, and the equivalent circle diameter of the TiC reinforcing phase is 3 μm~5 μm; the density of the injection-molded titanium alloy part is 99.0%~99.6%.

24. An injection-molded titanium alloy part, characterized in that, The injection-molded titanium alloy part is prepared according to the preparation method of any one of claims 20 to 22. The microstructure of the injection-molded titanium alloy part consists of 40% to 60% equiaxed α phase, island-like β phase, and dispersed fine TiC reinforcing phase; the island-like β phase is composed of precipitated nanoscale secondary α bundles, which are arranged in parallel and cross-distributed structures, and the thickness of the secondary α bundles is 50 nm to 100 nm; the equivalent circle diameter of the equiaxed α phase is 15 μm to 25 μm, and the equivalent circle diameter of the TiC reinforcing phase is 3 μm to 5 μm.

Images