Metal injection molding titanium alloy feedstock and method of making

Abstract

This invention relates to a metal injection molding titanium alloy feedstock and its preparation method. By mass percentage, its components include: 60%-75% Ti-6Al-4V powder; 15%-20% binder; and 10%-20% pore-forming agent. The binder, by mass percentage, includes: 55%-60% polyethylene glycol, 22%-26% polyvinylpyrrolidone, 10%-13% polyethylene glycol stearate, and 3%-8% mannitol. The use of a specialized binder solves the problems of poor compatibility with binders, easy agglomeration of the feedstock, uneven dispersion of the pore-forming agent, and low pore connectivity during porous structure preparation.

Description

Technical Field

[0001] This invention relates to the field of titanium and titanium alloy manufacturing technology, and in particular to a method for feeding and preparing titanium alloys for metal injection molding. Background Technology

[0002] Titanium and titanium alloys are widely used in high-end fields such as aerospace, chemical equipment, and medical devices due to their high specific strength, excellent corrosion resistance, and good biocompatibility. Metal injection molding (MIM) is the core process for manufacturing small and complex titanium parts, but the high reactivity of titanium alloys places stringent requirements on the binder system: it is prone to oxidation and oxygen absorption at high temperatures (rapid oxidation at >300℃), and excessive oxygen content will significantly reduce plasticity and fatigue performance; traditional paraffin-polypropylene binders are mixed at 160-200℃ and degreased at 400-500℃, making oxidation difficult to avoid; and when the degreasing residue is >0.5%, the sintering density is <95%, and the mechanical properties do not meet the standards. In addition, Ti-6Al-4V powder easily forms a TiO2 layer on its surface, which has poor compatibility with the binder and is prone to agglomeration during feeding; during the preparation of porous structures, the pore-forming agent is unevenly dispersed, resulting in low pore connectivity. Summary of the Invention

[0003] This invention provides a feeding material and preparation method for metal injection molding of titanium alloy. The feeding material uses a special binder, which can solve the problems of poor compatibility with binders, easy agglomeration of the feeding material, uneven dispersion of pore-forming agent and low pore connectivity during the preparation of porous structures.

[0004] This invention provides a metal injection molding titanium alloy feedstock, whose components, by mass percentage, include: 60%-75% Ti-6Al-4V powder; 15%-20% binder; and 10%-20% pore-forming agent. The adhesive, by weight percentage, includes: 55%-60% polyethylene glycol, 22%-26% polyvinylpyrrolidone, 10%-13% polyethylene glycol stearate, and 3%-8% mannitol.

[0005] Preferably, when the feed material is a lightweight structural component, it includes, by weight percentage: 60%-65% Ti-6Al-4V powder; 15%-20% binder; and 15%-20% pore-forming agent.

[0006] Preferably, when the feed is for load-bearing structural components, it comprises, by mass percentage: 70%-75% Ti-6Al-4V powder; 15%-20% binder; and 10%-15% pore-forming agent.

[0007] Preferably, when the feed material is a lightweight structural component, it comprises, by weight percentage: 63% Ti-6Al-4V powder; 17% binder; and 20% pore-forming agent.

[0008] Preferably, when the feed is for a load-bearing structural component, it comprises, by mass percentage: 73% Ti-6Al-4V powder; 17% binder; and 10% pore-forming agent.

[0009] Preferably, the pore-forming agent is one of sodium chloride microspheres or polymethyl methacrylate microspheres, and the particle size of the pore-forming agent is 50-450 μm.

[0010] A method for preparing a titanium alloy feedstock for metal injection molding includes: Step 1. Adhesive preparation: Add 55%-60% polyethylene glycol, 22%-26% polyvinylpyrrolidone, 10%-13% polyethylene glycol stearate, and 3%-8% mannitol to a high-speed mixer and stir to obtain the adhesive. Step 2. Powder pretreatment: Vacuum dry Ti-6Al-4V powder at 80-100℃ for 2-3 hours, and sieve out Ti-6Al-4V powder with a particle size of 10-50μm; Dry the pore-forming agent at 60-80℃ for 1-2 hours. Step 3. Mixing: Weigh the following ingredients according to the following mass percentages: 60%-75% pretreated Ti-6Al-4V powder; 15%-20% prepared binder; 10%-20% pretreated pore-forming agent; add the weighed pretreated Ti-6Al-4V powder and pore-forming agent to a ball mill, and mix and ball mill at low speed for 2 hours under argon protection. Then, sieve the mixture to obtain a mixed powder. Step 4. Mixing: Add the mixed powder and weighed binder to the internal mixer and mix at 85-95℃ for 45 minutes. Step 5. Extrusion granulation: The internally mixed material after internal mixing is fed into an extrusion granulator for granulation. The material is cut at a temperature of 90-110℃ to obtain feed pellets. Step 6. Injection molding: The obtained feed pellets are fed into an injection molding machine for injection molding. The injection temperature is 90-110℃, the mold temperature is 40-60℃, the injection pressure is 50-100MPa, and the holding pressure is 10-20s to obtain the injection sample. Step 7. Finished product: The injection sample is degreased and sintered to obtain the feed product.

[0011] Preferably, in step 1, when preparing the binder, the high-speed mixer containing the added material is stirred for 5 minutes at a speed of 20-25 r / min at a temperature of 85-90°C, and then stirred for 10 minutes at a speed of 35-40 r / min until the mixture is uniform and transparent. After that, the mixture is cooled and pulverized to obtain the binder.

[0012] Preferably, during the mixing process in step 2, the binder is first added to the internal mixer and heated to 85-95°C to completely melt it. Then, the mixed powder is added in three batches, with a 10-minute interval between each batch.

[0013] Preferably, step 7 includes degreasing and sintering; Degreasing: The obtained feed sample is first soaked in n-heptane at 40℃ for 20h for solvent degreasing to remove part of the polyethylene glycol PEG-2000; then thermal degreasing is carried out under vacuum or argon atmosphere, with a heating rate of 1-2℃ / min, holding at 280-300℃ for 2h, and holding at 400℃ for 1h. Sintering was carried out in a vacuum sintering furnace for degreased samples at a temperature of 1250-1300℃ and a vacuum degree of 10. -3 Pa, sintered for 2 hours and then cooled in the furnace.

[0014] The beneficial effects of this invention are as follows: (1) Ti-6Al-4V special low-temperature binder system; The binder is a quaternary system of polyethylene glycol PEG-2000 / polyvinylpyrrolidone PVP K30 / polyethylene glycol stearate PEG-SA / D-mannitol, designed for the high activity and easy oxidation characteristics of Ti-6Al-4V. PEG-2000 encapsulates the powder at low viscosity at 90℃ and decomposes at 200℃ to achieve low-temperature debinding at 280-300℃, avoiding rapid oxidation of Ti-6Al-4V at >300℃. PVP K30 forms hydrogen bonds with the TiO2 surface, solving the problem of Ti-6Al-4V powder agglomeration. PEG-SA reduces injection molding shear and minimizes powder damage. D-mannitol sublimates to promote debinding. The quaternary synergy results in an oxygen content of <0.25% in Ti-6Al-4V (comparative example 0.35%) and a density of 96%-97% (traditional 94%-95%), meeting the stringent standard of <0.30% oxygen content for aerospace-grade Ti-6Al-4V.

[0015] (2) Mannitol's synergistic mechanism for oxygen control; D-Mannitol synergistically with polyvinylpyrrolidone (PVP) K30: anchors microcrystals to prevent agglomeration, fills gaps to prevent Ti-6Al-4V powder sedimentation, and achieves a pore-forming agent dispersion CV < 10%. D-Mannitol sublimates at 166-170℃ to form microporous channels, reducing the degreasing temperature of Ti-6Al-4V to 280-300℃ (compared to the traditional 400-500℃), shortening the degreasing time by 40%, and achieving a residual rate of 0.15%-0.20%, thus controlling oxygen increment at the source. Synergistically with polyethylene glycol stearate (PEG-SA) ensures pore connectivity. The dosage is strictly limited to 2.5%-3.5%; exceeding this amount will cause recrystallization and damage the compactness of the Ti-6Al-4V matrix.

[0016] 3) Ti-6Al-4V full-process argon protection process: Argon protection (0.1-0.5MPa, 20 L / min) throughout the mixing, kneading, and granulation processes, combined with low-temperature kneading at 85-95℃ and low-temperature degreasing at 280-300℃, achieves precise control of the oxygen content of Ti-6Al-4V to <0.25%, meeting the requirements of high-end applications.

[0017] (4) Ti-6Al-4V gradient performance control: For the two application scenarios of Ti-6Al-4V, namely lightweight and load-bearing, the porosity is controlled by adjusting the proportion of pore-forming agent to 30%-70% and the oxygen content is kept stable at <0.25%, so as to achieve precise design of Ti-6Al-4V parts performance. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, the following description is provided in conjunction with exemplary embodiments, including various details of the embodiments of the present invention to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description. Example 1

[0019] This embodiment provides a titanium alloy feedstock for metal injection molding, which, by mass percentage, comprises: 60%-75% Ti-6Al-4V powder; 15%-20% binder; and 10%-20% pore-forming agent. In this embodiment, the Ti-6Al-4V powder has a particle size of 10-50 μm and an oxygen content of <0.15%; the pore-forming agent is selected from either sodium chloride (NaCl) microspheres or polymethyl methacrylate (PMMA) microspheres, with a particle size of 50-450 μm.

[0020] The binder, by mass percentage, comprises: 55%-60% polyethylene glycol, 22%-26% polyvinylpyrrolidone, 10%-13% polyethylene glycol stearate, and 3%-8% mannitol. In this embodiment, polyethylene glycol PEG-2000 is used as the main binder, with a viscosity <1 Pa·s at 90°C and decomposition starting at 200°C, thus preventing high-temperature oxidation of Ti-6Al-4V. Polyvinylpyrrolidone PVP K30 is used as the dispersant in the binder; the pyrrolidone groups in PVP K30 are hydrogen-bonded to the TiO2 surface, improving the dispersion of Ti-6Al-4V powder. Polyvinyl glycol stearate PEG-SA is used as a lubricant in the binder, reducing injection pressure by 15%-20% and reducing shear damage to Ti-6Al-4V powder. D-mannitol is used as a degreasing accelerator in the binder, sublimating at 166°C-170°C to form channels and completing degreasing at 280°C-300°C.

[0021] The quaternary system of polyethylene glycol (PEG-2000), polyvinylpyrrolidone (PVP K30), polyethylene glycol stearate (PEG-SA), and D-mannitol in this embodiment is designed to address the high activity and easy oxidation characteristics of Ti-6Al-4V. PEG-2000 encapsulates the powder at low viscosity at 90°C and initiates decomposition at 200°C, achieving low-temperature degreasing at 280-300°C, thus preventing rapid oxidation of Ti-6Al-4V above 300°C. PVP K30 forms hydrogen bonds with the TiO2 surface, solving the problem of Ti-6Al-4V powder agglomeration. PEG-SA reduces injection molding shear, minimizing powder damage. D-mannitol sublimates to promote degreasing.

[0022] D-Mannitol synergistically with polyvinylpyrrolidone (PVP) K30: anchors microcrystals to prevent agglomeration, fills gaps to prevent Ti-6Al-4V powder sedimentation, and achieves a pore-forming agent dispersion CV < 10%. D-Mannitol sublimates at 166-170℃ to form microporous channels, reducing the degreasing temperature of Ti-6Al-4V to 280-300℃ (compared to the traditional 400-500℃), shortening the degreasing time by 40%, and achieving a residual rate of 0.15%-0.20%, thus controlling oxygen increment at the source. Synergistically with polyethylene glycol stearate (PEG-SA) ensures pore connectivity. The dosage is strictly limited to 2.5%-3.5%; exceeding this amount will cause recrystallization and damage the compactness of the Ti-6Al-4V matrix.

[0023] In one embodiment, when the feedstock is used as a lightweight structure, the feedstock components of the lightweight structure include, by weight percentage: 60%-65% Ti-6Al-4V powder; 15%-20% binder; 15%-20% pore-forming agent; in a specific embodiment, by weight percentage, it includes: 63% Ti-6Al-4V powder; 17% binder; 20% pore-forming agent.

[0024] In one embodiment, when the feedstock is used as a load-bearing structural component, the feedstock components of the load-bearing structure include, by mass percentage: 70%-75% Ti-6Al-4V powder; 15%-20% binder; 10%-15% pore-forming agent; in a specific embodiment, by mass percentage, it includes: 73% Ti-6Al-4V powder; 17% binder; 10% pore-forming agent. Example 2

[0025] This embodiment discloses a method for preparing a titanium alloy feedstock for metal injection molding. The feedstock prepared by this method is intended for use as a lightweight structural component; the target porosity is 50%-70%, and the target oxygen content is <0.25%. The specific preparation method includes: Step 1. Adhesive preparation: Add 55% polyethylene glycol, 26% polyvinylpyrrolidone, 13% polyethylene glycol stearate, and 6% mannitol to a high-speed mixer and stir to obtain the adhesive. Specifically, during the preparation process, ensure that the temperature of the high-speed mixer is 85-90℃. When stirring, first stir at a speed of 20-25r / min for 5 minutes, then stir at a speed of 35-40r / min for 10 minutes until the mixture is uniform and transparent. Then cool and pulverize to obtain the binder, and seal and store the obtained binder. Step 2. Powder pretreatment: Ti-6Al-4V powder is vacuum dried at 100℃ for 2 hours, and Ti-6Al-4V powder with a particle size of 50μm is sieved out; the pore-forming agent is dried at 80℃ for 1 hour; the pretreatment of Ti-6Al-4V powder and pore-forming agent powder is completed. In this embodiment, the pore-forming agent is selected from either sodium chloride (NaCl) microspheres or polymethyl methacrylate (PMMA) microspheres with a particle size of 50μm. Step 3. Mixing: Weigh the following ingredients according to the following mass percentages: 60% pretreated Ti-6Al-4V powder; 20% prepared binder; 20% pretreated pore-forming agent; and add the weighed pretreated Ti-6Al-4V powder and pore-forming agent to a ball mill. During ball milling, the mixing medium is anhydrous ethanol, and the mixture is ball-milled at low speed for 2 hours under argon protection. After that, the mixed powder is obtained by screening through a 300-mesh sieve. Step 4. Mixing: Add the screened mixed powder and weighed binder into an internal mixer and mix them. During the mixing process, protect the mixture with an argon atmosphere (0.5MPa, 20L / min). Mix at a mixing temperature of 85-95℃ for 45 minutes and control the speed of the internal mixer at 20-40rpm. Specifically, during the mixing process, the weighed binder is first added to the mixer, and then the temperature of the mixer is heated to 90°C. The mixed powder is then added to the mixer in three batches, with an interval of 10 minutes between each batch. By adding the powder in batches, it can be ensured that the Ti-6Al-4V powder and the pore-forming agent are evenly dispersed in the binder.

[0026] Step 5. Extrusion granulation: The internally mixed material is fed into an extrusion granulator for granulation. During granulation, an argon atmosphere of 0.5 MPa and 20 L / min is introduced. The material is cut at a temperature of 90-110℃ and a cutting speed of 100 rpm. The introduced argon atmosphere can cool the material during the cutting process and prevent high-temperature oxidation. The particle size of the feed pellets obtained after cutting is 2-5 mm, and the feed pellets are sealed and stored. Step 6. Injection molding: The obtained feed pellets are fed into an injection molding machine for injection molding. The injection temperature is 90-110℃, the mold temperature is 40-60℃, the injection pressure is 50-100MPa, and the holding pressure is 10-20s to obtain the injection sample. Step 7. Degreasing: The injection sample is first soaked in n-heptane at 40℃ for 20h for solvent degreasing to remove some of the polyethylene glycol PEG-2000; then it is thermally degreased under vacuum or argon atmosphere, with a heating rate of 1-2℃ / min, held at 280-300℃ for 2h, and held at 400℃ for 1h.

[0027] Step 8. Sintering: Sinter the degreased sample in a vacuum sintering furnace at a temperature of 1250-1300℃ and a vacuum degree of 10. -3 Pa, after sintering for 2 hours, was cooled in the furnace to obtain the sample. Example 3

[0028] This embodiment discloses a method for preparing a titanium alloy feedstock for metal injection molding. The feedstock prepared by this method is intended for use as a lightweight structural component; the target porosity is 50%-70%, and the target oxygen content is <0.25%. The specific preparation method includes: Step 1. Adhesive preparation: Add 60% polyethylene glycol, 22% polyvinylpyrrolidone, 10% polyethylene glycol stearate, and 8% mannitol to a high-speed mixer and stir to obtain the adhesive. Specifically, during the preparation process, ensure that the temperature of the high-speed mixer is 85-90℃. When stirring, first stir at a speed of 20-25r / min for 5 minutes, then stir at a speed of 35-40r / min for 10 minutes until the mixture is uniform and transparent. Then cool and pulverize to obtain the binder, and seal and store the obtained binder. Step 2. Powder pretreatment: Ti-6Al-4V powder is vacuum dried at 80℃ for 3 hours, and Ti-6Al-4V powder with a particle size of 10-50μm is sieved out; the pore-forming agent is dried at 60℃ for 2 hours; the pretreatment of Ti-6Al-4V powder and pore-forming agent powder is completed. In this embodiment, the pore-forming agent is selected from either sodium chloride NaCl microspheres or polymethyl methacrylate PMMA microspheres with a particle size of 450μm. Step 3. Mixing: Weigh the following ingredients according to the following mass percentages: 63% pretreated Ti-6Al-4V powder; 17% prepared binder; 20% pretreated pore-forming agent; and add the weighed pretreated Ti-6Al-4V powder and pore-forming agent to a ball mill. During ball milling, the mixing medium is anhydrous ethanol, and the mixture is ball-milled at low speed for 2 hours under argon protection. The resulting powder is then sieved through a 300-mesh sieve. Step 4. Mixing: Add the screened mixed powder and weighed binder into an internal mixer and mix them. During the mixing process, protect the mixture with an argon atmosphere (0.5MPa, 20L / min). Mix at a mixing temperature of 85-95℃ for 45 minutes and control the speed of the internal mixer at 20-40rpm. Specifically, during the mixing process, the weighed binder is first added to the mixer, and then the temperature of the mixer is heated to 95°C. The mixed powder is then added to the mixer in three batches, with an interval of 10 minutes between each batch. By adding the powder in batches, it can be ensured that the Ti-6Al-4V powder and the pore-forming agent are evenly dispersed in the binder.

[0029] Step 5. Extrusion granulation: The internally mixed material is fed into an extrusion granulator for granulation. During granulation, an argon atmosphere of 0.5 MPa and 20 L / min is introduced. The material is cut at a temperature of 90-110℃ and a cutting speed of 100 rpm. The introduced argon atmosphere can cool the material during the cutting process and prevent high-temperature oxidation. The particle size of the feed pellets obtained after cutting is 2-5 mm, and the feed pellets are sealed and stored. Step 6. Injection molding: The obtained feed pellets are fed into an injection molding machine for injection molding. The injection temperature is 90-110℃, the mold temperature is 40-60℃, the injection pressure is 50-100MPa, and the holding pressure is 10-20s to obtain the injection sample. Step 7. Degreasing: The injection sample is first soaked in n-heptane at 40℃ for 20h for solvent degreasing to remove some of the polyethylene glycol PEG-2000; then it is thermally degreased under vacuum or argon atmosphere, with a heating rate of 1-2℃ / min, held at 280-300℃ for 2h, and held at 400℃ for 1h.

[0030] Step 8. Sintering: The degreased sample is sintered in a vacuum sintering furnace at a temperature of 1250-1300℃ and a vacuum degree of 10. -3 Pa, after sintering for 2 hours, was cooled in the furnace to obtain the sample. Example 4

[0031] This embodiment discloses a method for preparing a titanium alloy feedstock for metal injection molding. The feedstock prepared by this method is intended for use as a load-bearing structural component; the target porosity is 30%-45%, and the target oxygen content is <0.20%. The specific preparation method includes: Step 1. Adhesive preparation: Add 58% polyethylene glycol, 24% polyvinylpyrrolidone, 12% polyethylene glycol stearate, and 6% mannitol to a high-speed mixer and stir to obtain the adhesive. Specifically, during the preparation process, ensure that the temperature of the high-speed mixer is 85-90℃. When stirring, first stir at a speed of 20-25r / min for 5 minutes, then stir at a speed of 35-40r / min for 10 minutes until the mixture is uniform and transparent. Then cool and pulverize to obtain the binder, and seal and store the obtained binder. Step 2. Powder pretreatment: Ti-6Al-4V powder is vacuum dried at 90℃ for 2.5h, and Ti-6Al-4V powder with a particle size of 10-50μm is sieved out; the pore-forming agent is dried at 70℃ for 1h; the pretreatment of Ti-6Al-4V powder and pore-forming agent powder is completed. In this embodiment, the pore-forming agent is selected as either sodium chloride NaCl microspheres or polymethyl methacrylate PMMA microspheres with a particle size of 250μm. Step 3. Mixing: Weigh the following ingredients according to the following mass percentages: 75% pretreated Ti-6Al-4V powder; 15% prepared binder; 10% pretreated pore-forming agent; and add the weighed pretreated Ti-6Al-4V powder and pore-forming agent to a ball mill. During ball milling, the mixing medium is anhydrous ethanol, and the mixture is ball-milled at low speed for 2 hours under argon protection. The resulting powder is then screened through a 300-mesh sieve. Step 4. Mixing: Add the screened mixed powder and weighed binder into an internal mixer and mix them. During the mixing process, protect the mixture with an argon atmosphere (0.5MPa, 20L / min). Mix at a mixing temperature of 95℃ for 45 minutes and control the speed of the internal mixer at 20-40rpm. Specifically, during the mixing process, the weighed binder is first added to the mixer, and then the temperature of the mixer is heated to 95°C. The mixed powder is then added to the mixer in three batches, with an interval of 10 minutes between each batch. By adding the powder in batches, it can be ensured that the Ti-6Al-4V powder and the pore-forming agent are evenly dispersed in the binder.

[0032] Step 5. Extrusion granulation: The internally mixed material is fed into an extrusion granulator for granulation. During granulation, an argon atmosphere of 0.5 MPa and 20 L / min is introduced. The material is cut at 110°C and a cutting speed of 100 rpm. The introduced argon atmosphere can cool the material during the cutting process and prevent high-temperature oxidation. The particle size of the feed pellets obtained after cutting is 2-5 mm. The feed pellets are then sealed and stored. Step 6. Injection molding: The obtained feed pellets are fed into an injection molding machine for injection molding. The injection temperature is 110℃, the mold temperature is 60℃, the injection pressure is 50-100MPa, and the holding pressure is 10-20s to obtain the injection sample. Step 7. First, soak the injection sample in n-heptane at 40℃ for 20h to remove some of the polyethylene glycol PEG-2000; then perform thermal degreasing under vacuum or argon atmosphere, with a heating rate of 1-2℃ / min, holding at 280-300℃ for 2h, and holding at 400℃ for 1h.

[0033] Step 8. Sintering: Sinter the degreased sample in a vacuum sintering furnace at a temperature of 1250-1300℃ and a vacuum degree of 10. -3 Pa, after sintering for 2 hours, was cooled in the furnace to obtain the sample. Example 5

[0034] This embodiment discloses a method for preparing a titanium alloy feedstock for metal injection molding. The feedstock prepared by this method is intended for use as a load-bearing structural component; the target porosity is 30%-45%, and the target oxygen content is <0.20%. The specific preparation method includes: Step 1. Adhesive preparation: Add 60% polyethylene glycol, 26% polyvinylpyrrolidone, 11% polyethylene glycol stearate, and 3% mannitol to a high-speed mixer and stir to obtain the adhesive. Specifically, during the preparation process, ensure that the temperature of the high-speed mixer is 85-90℃. When stirring, first stir at a speed of 20-25r / min for 5 minutes, then stir at a speed of 35-40r / min for 10 minutes until the mixture is uniform and transparent. Then cool and pulverize to obtain the binder, and seal and store the obtained binder. Step 2. Powder pretreatment: Ti-6Al-4V powder is vacuum dried at 90℃ for 2.5h, and Ti-6Al-4V powder with a particle size of 10-50μm is sieved out; the pore-forming agent is dried at 70℃ for 1h; the pretreatment of Ti-6Al-4V powder and pore-forming agent powder is completed. In this embodiment, the pore-forming agent is selected as either sodium chloride NaCl microspheres or polymethyl methacrylate PMMA microspheres with a particle size of 250μm. Step 3. Mixing: Weigh the following ingredients according to the following mass percentages: 70% pretreated Ti-6Al-4V powder; 17% prepared binder; 13% pretreated pore-forming agent; and add the weighed pretreated Ti-6Al-4V powder and pore-forming agent to a ball mill. During ball milling, the mixing medium is anhydrous ethanol, and the mixture is ball-milled at low speed for 2 hours under argon protection. The resulting powder is then sieved through a 300-mesh sieve. Step 4. Mixing: Add the screened mixed powder and weighed binder into an internal mixer and mix them. During the mixing process, protect the mixture with an argon atmosphere (0.5MPa, 20L / min). Mix at a mixing temperature of 95℃ for 45 minutes and control the speed of the internal mixer at 20-40rpm. Specifically, during the mixing process, the weighed binder is first added to the mixer, and then the temperature of the mixer is heated to 95°C. The mixed powder is then added to the mixer in three batches, with an interval of 10 minutes between each batch. By adding the powder in batches, it can be ensured that the Ti-6Al-4V powder and the pore-forming agent are evenly dispersed in the binder.

[0035] Step 5. Extrusion granulation: The internally mixed material is fed into an extrusion granulator for granulation. During granulation, an argon atmosphere of 0.5 MPa and 20 L / min is introduced. The material is cut at 110°C and a cutting speed of 100 rpm. The introduced argon atmosphere can cool the material during the cutting process and prevent high-temperature oxidation. The particle size of the feed pellets obtained after cutting is 2-5 mm. The feed pellets are then sealed and stored. Step 6. Injection molding: The obtained feed pellets are fed into an injection molding machine for injection molding. The injection temperature is 110℃, the mold temperature is 60℃, the injection pressure is 50-100MPa, and the holding pressure is 10-20s to obtain the injection sample. Step 7. Degreasing: The injection sample is first soaked in n-heptane at 40℃ for 20h for solvent degreasing to remove some of the polyethylene glycol PEG-2000; then it is thermally degreased under vacuum or argon atmosphere, with a heating rate of 1-2℃ / min, held at 280-300℃ for 2h, and held at 400℃ for 1h.

[0036] (9) Sintering: The degreased sample is sintered in a vacuum sintering furnace at a temperature of 1250-1300℃ and a vacuum degree of 10. -3 Pa, after sintering for 2 hours, was cooled in the furnace to obtain the sample.

[0037] Comparative Example 1 A method for preparing feedstock as a lightweight structural component is provided, the difference between this method and Example 2 is that the binder does not contain mannitol.

[0038] Comparative Example 2 A method for preparing lightweight structural component feedstock is provided, the difference between this method and Example 3 is that the binder is polyethylene glycol.

[0039] Comparative Example 3 This comparative example provides a method for preparing a load-bearing structural component feedstock. The difference between this method and Example 4 is that the mannitol content in the binder is 10%.

[0040] The porosity, compressive strength, density, oxygen content, and tensile strength of the samples prepared in Examples 2, 3, 4, 5, and Comparative Examples 1, 2, and 3 were tested; the test structures are shown in Table 1. Table 1 shows the sample performance test results; sample Application scenarios Porosity compressive strength Density Oxygen content tensile strength Example 2 Lightweight 58% 385 MPa 96.20% 0.22% 890 MPa Example 3 Lightweight 62% 360 MPa 96.50% 0.20% 905 MPa Example 4 load-bearing capacity 38% 520 MPa 97.10% 0.18% 1020 MPa Example 5 load-bearing capacity 42% 495 MPa 96.80% 0.21% 980 MPa Comparative Example 1 Lightweight 55% 320 MPa 94.50% 0.35% 820 MPa Comparative Example 2 — — Unable to form — — — Comparative Example 3 Lightweight 72% 195 MPa 92.30% 0.28% 750 MPa The above tests show that the lightweight structural components and load-bearing structural components prepared in this application have significantly higher porosity, compressive strength, density, oxygen content, and tensile strength than the samples prepared in Comparative Examples 1, 2, and 3.

[0041] It can be seen that this application has the following effects: 1. Ti-6Al-4V dedicated low-temperature binder system; The binder is a quaternary system of polyethylene glycol PEG-2000 / polyvinylpyrrolidone PVP K30 / polyethylene glycol stearate PEG-SA / D-mannitol, designed to address the high activity and easy oxidation characteristics of Ti-6Al-4V. PEG-2000 encapsulates the powder at low viscosity at 90℃ and initiates decomposition at 200℃, achieving low-temperature debinding at 280-300℃, thus preventing rapid oxidation of Ti-6Al-4V above 300℃. PVP K30 forms hydrogen bonds with the TiO2 surface, solving the problem of Ti-6Al-4V powder agglomeration. PEG-SA reduces injection molding shear, minimizing powder damage. D-mannitol sublimates to promote debinding. The quaternary synergy results in an oxygen content of <0.25% in Ti-6Al-4V (comparative example 0.35%) and a density of 96%-97% (traditional 94%-95%), meeting the stringent standard of <0.30% oxygen content for aerospace-grade Ti-6Al-4V.

[0042] 2. Mannitol's synergistic mechanism of oxygen regulation D-Mannitol synergistically with polyvinylpyrrolidone (PVP) K30: anchors microcrystals to prevent agglomeration, fills gaps to prevent Ti-6Al-4V powder sedimentation, and achieves a pore-forming agent dispersion CV < 10%. D-Mannitol sublimates at 166-170℃ to form microporous channels, reducing the degreasing temperature of Ti-6Al-4V to 280-300℃ (compared to the traditional 400-500℃), shortening the degreasing time by 40%, and achieving a residual rate of 0.15%-0.20%, thus controlling oxygen increment at the source. Synergistically with polyethylene glycol stearate (PEG-SA) ensures pore connectivity. The dosage is strictly limited to 2.5%-3.5%; exceeding this amount will cause recrystallization and damage the compactness of the Ti-6Al-4V matrix.

[0043] 3. Ti-6Al-4V full-process argon protection process: Argon protection (0.1-0.5 MPa, 20 L / min) throughout the mixing, kneading, and granulation processes, combined with low-temperature kneading at 85-95℃ and low-temperature degreasing at 280-300℃, achieves precise control of the oxygen content of Ti-6Al-4V to <0.25%, meeting the requirements of high-end applications.

[0044] 4. Ti-6Al-4V Gradient Performance Control: For both lightweight and load-bearing applications of Ti-6Al-4V, the porosity is controlled by adjusting the proportion of pore-forming agent to 30%-70%, and the oxygen content is kept stable at <0.25%, thus achieving precise design of Ti-6Al-4V parts.

[0045] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in conjunction with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as set forth in the appended claims.

Claims

1. A feedstock for metal injection molding of titanium alloys, characterized in that, By weight percentage, its components include: 60%-75% Ti-6Al-4V powder; 15%-20% binder; and 10%-20% pore-forming agent. The adhesive, by weight percentage, includes: 55%-60% polyethylene glycol, 22%-26% polyvinylpyrrolidone, 10%-13% polyethylene glycol stearate, and 3%-8% mannitol.

2. The metal injection molding titanium alloy feedstock according to claim 1, characterized in that, When the feedstock is for lightweight structural components, it includes, by weight percentage: 60%-65% Ti-6Al-4V powder; 15%-20% binder; and 15%-20% pore-forming agent.

3. The metal injection molding titanium alloy feedstock according to claim 1, characterized in that, When the feed material is for load-bearing structural components, it includes, by mass percentage: 70%-75% Ti-6Al-4V powder; 15%-20% binder; and 10%-15% pore-forming agent.

4. The titanium alloy feedstock for metal injection molding according to claim 2, characterized in that, When the feedstock is for lightweight structural components, it includes, by weight percentage: 63% Ti-6Al-4V powder; 17% binder; and 20% pore-forming agent.

5. The metal injection molding titanium alloy feedstock according to claim 3, characterized in that, When the feed material is for load-bearing structural components, it includes, by mass percentage: 73% Ti-6Al-4V powder; 17% binder; and 10% pore-forming agent.

6. The titanium alloy feedstock for metal injection molding according to claim 1, characterized in that, The pore-forming agent is either sodium chloride microspheres or polymethyl methacrylate microspheres, and the particle size of the pore-forming agent is 50 μm-450 μm.

7. A method for preparing a titanium alloy feedstock for metal injection molding, characterized in that, include: Step 1. Adhesive preparation: Add 55%-60% polyethylene glycol, 22%-26% polyvinylpyrrolidone, 10%-13% polyethylene glycol stearate, and 3%-8% mannitol to a high-speed mixer and stir to obtain the adhesive. Step 2. Powder pretreatment: Vacuum dry Ti-6Al-4V powder at 80-100℃ for 2-3 hours, and sieve out Ti-6Al-4V powder with a particle size of 10μm-50μm; Dry the pore-forming agent at 60-80℃ for 1-2 hours. Step 3. Mixing: Weigh the following ingredients according to the following mass percentages: 60%-75% pretreated Ti-6Al-4V powder; 15%-20% prepared binder; 10%-20% pretreated pore-forming agent; add the weighed pretreated Ti-6Al-4V powder and pore-forming agent to a ball mill, and mix and ball mill at low speed for 2 hours under argon protection. Then, sieve the mixture to obtain a mixed powder. Step 4. Mixing: Add the mixed powder and weighed binder to the internal mixer and mix at 85-95℃ for 45 minutes. Step 5. Extrusion granulation: The internally mixed material after internal mixing is fed into an extrusion granulator for granulation. The material is cut at a temperature of 90-110℃ to obtain feed pellets. Step 6. Injection molding: The obtained feed pellets are fed into an injection molding machine for injection molding. The injection temperature is 90-110℃, the mold temperature is 40-60℃, the injection pressure is 50-100 MPa, and the holding pressure is 10-20s to obtain the injection sample. Step 7. Finished product: The injection sample is degreased and sintered to obtain the feed product.

8. The method for preparing the metal injection molding titanium alloy feedstock according to claim 7, characterized in that, In step 1, when preparing the binder, the materials are added to a high-speed mixer and stirred at 20-25 r / min for 5 minutes at a temperature of 85-90℃, and then stirred at 35-40 r / min for 10 minutes until the mixture is uniform and transparent. After that, the mixture is cooled and pulverized to obtain the binder.

9. The method for preparing the titanium alloy feedstock for metal injection molding according to claim 7, characterized in that, In step 2, when mixing, the binder is first added to the internal mixer and heated to 85-95℃ to completely melt it. Then, the mixed powder is added in 3 batches, with an interval of 10 minutes between each batch.

10. The method for preparing the metal injection molding titanium alloy feedstock according to claim 7, characterized in that, Step 7 includes degreasing and sintering; Degreasing: The obtained feed sample is first soaked in n-heptane at 40℃ for 20h for solvent degreasing to remove part of the polyethylene glycol PEG-2000; then thermal degreasing is carried out under vacuum or argon atmosphere, with a heating rate of 1-2℃ / min, holding at 280-300℃ for 2h, and holding at 400℃ for 1h. Sintering: The degreased sample was sintered in a vacuum sintering furnace at a temperature of 1250-1300℃ and a vacuum degree of 10. -3 Pa, sintered for 2 hours and then cooled in the furnace.