Titanium alloy feeding implant and preparation method thereof

Abstract

The invention discloses a titanium alloy feeding implant and a preparation method thereof, and the preparation method comprises the following steps: carrying out activating treatment on a biodegradable bonding system in an inert gas environment to form an expansion-state binder precursor, and then mixing titanium alloy powder and the precursor which are proportioned in stages in a multi-stage mixing device in stages to obtain the titanium alloy feeding implant. Sequentially executing low-temperature activation, melting and dispersing operations to prepare uniform feed; carrying out vibration-assisted injection molding on the feed to generate a green body with a multi-stage pore structure; removing the binder step by step and reserving pores by adopting a synergistic degreasing process of supercritical fluid extraction, microwave decomposition and gas phase cleaning; densification sintering molding of the titanium alloy implant is realized through pre-sintering and plasma activating treatment, so that an implant finished product is formed; according to the process, through the coupling design of innovation of a biodegradable binder system and an intelligent degreasing process, on the premise that the biological safety of the titanium alloy implant is ensured, precise forming and sintering densification control of a complex pore structure are synchronously achieved.

Description

Technical Field

[0001] The present invention relates to the field of medical implants, and particularly to a titanium alloy feedstock implant and a preparation method thereof. Background Art

[0002] As the core material of the metal injection molding (MIM) technology, the titanium alloy feedstock implant has important application value in the field of medical implant manufacturing. Orthopedic implants (such as artificial joints, bone plates, etc.) require materials to have excellent biocompatibility, bionic porous structure (to promote the growth of bone cells) and the ability to reproduce precise structures. In traditional processes, the titanium alloy feedstock needs to be compounded with a binder and powder to achieve injection molding. However, the coordinated control of the complex pore design (porosity 30 - 70%, pore diameter 50 - 300 μm) and biosecurity (no toxic residues) of the implant has always been a technical bottleneck faced by the industry.

[0003] Existing titanium alloy feedstock preparation technologies mostly adopt a mixed system of polyolefin binders and titanium powders with a single particle size, and rely on thermal debinding or solvent debinding processes to remove the binder. For example, a titanium alloy injection molding feedstock uses a two-step thermal debinding method, first decomposing part of the binder at 200°C and then completely removing it at a high temperature of 450°C. However, such methods are prone to pore structure collapse due to temperature gradients during the debinding stage, and the hydrocarbon residues generated by high-temperature decomposition will significantly increase the oxygen content on the surface of the implant. Especially for the bionic porous structure, the existing debinding processes are difficult to maintain the integrity of the pore morphology while removing the binder, seriously restricting the bone integration performance and long-term stability of the implant.

[0004] In view of this, it is necessary to improve the existing titanium alloy feedstock preparation technology to solve the technical problems of pore collapse and residual toxic substances caused by the debinding process. Summary of the Invention

[0005] The purpose of the present invention is to provide a titanium alloy feedstock implant and a preparation method thereof to solve the above technical problems.

[0006] To achieve this purpose, the present invention adopts the following technical solutions: A preparation method of a titanium alloy feedstock implant includes the following steps: S1, placing a biodegradable binder system containing a main binder, a plasticizer and a sacrificial template material in an inert gas environment for activation treatment to form an expanded binder precursor; S2, mixing titanium alloy powders with the expanded binder precursor according to a preset particle size ratio in a multi-stage mixing device, and sequentially performing low-temperature activation, medium-temperature melting and high-speed dispersion operations to obtain a uniform feedstock; S3. Inject the prepared uniform feedstock into a mold with a preset shape, and complete injection molding under vibration-assisted conditions to obtain a green body with a multi-level pore structure. S4. Perform multi-stage debinding on the obtained green body, successively using supercritical fluid extraction, microwave catalytic decomposition, and gas-phase cleaning processes to gradually remove the binder components and retain the pore structure, forming a debound body. S5. Place the debound body in a vacuum sintering furnace, first perform pre-sintering treatment, then introduce a reactive plasma for surface activation, and complete densification sintering at high temperature to obtain a finished titanium alloy implant.

[0007] Optionally, the biodegradable binder system includes: The main binder is a biodegradable polyester, selected from at least one of polylactic acid, polycaprolactone, and polyglycolic acid, accounting for 35 - 45 wt% of the total mass of the binder system. The plasticizer is a biocompatible ester compound, selected from at least one of citrate ester, acetyl citrate ester, and polyethylene glycol, accounting for 10 - 20 wt% of the total mass of the binder system. The sacrificial template material is a swellable biopolymer, selected from at least one of alginate, gelatin, and starch-based porous microspheres, accounting for 3 - 8 wt% of the total mass of the binder system.

[0008] Optionally, the sum of the mass fractions of the components of the binder system is 80 - 95 wt%, and the balance is processing aids.

[0009] Optionally, step S1 specifically includes the following steps: S11. Mix the main binder particles and the plasticizer in a preset ratio, place them in a vacuum drying oven, and dry them at 80 - 100 °C for 2 - 4 hours to remove adsorbed moisture and volatile impurities, obtaining a pretreated binder mixture. S12. Transfer the pretreated binder mixture to a closed reaction kettle, introduce nitrogen to displace the air, and then heat it at a rate of 5 - 8 °C / min to 60 - 80 °C and keep it at a constant temperature for 30 - 60 minutes to allow the plasticizer to penetrate into the molecular chain gaps of the main binder, forming a pre-swollen complex. S13. Add the sacrificial template material to the pre-swollen complex, apply ultrasonic vibration for 10 - 20 minutes under nitrogen protection to uniformly disperse and embed the sacrificial template material into the main binder network structure, forming a porous precursor substrate. S14. Place the porous precursor substrate in a nitrogen environment with a humidity of 80 - 90% and let it stand for 8 - 12 hours, and control the temperature fluctuation range to allow the sacrificial template material to absorb moisture and swell to 120 - 150% of its original volume, obtaining a swollen binder precursor with open pore channels.

[0010] Optionally, step S2 specifically includes the following steps: S21. Place the titanium alloy powder with a preset particle size ratio in a vacuum drying oven, and dry it at 120 - 150 °C for 1 - 2 hours to remove the surface adsorbed moisture and obtain activated titanium powder; S22. Add the expanded binder precursor into a double planetary mixer, control the mixing temperature at 80 - 100 °C, and mix at a first low speed for 10 - 15 minutes to form a viscoelastic matrix; S23. Add the titanium alloy coarse powder with the first particle size into the viscoelastic matrix in three portions, with an interval of 5 - 8 minutes between each addition. Maintain the mixing temperature at 80 - 100 °C, and increase the rotation speed to the second medium speed. Continuously mix until the preset torque fluctuation range is reached after each powder addition to form a primary composite feed; S24. Raise the temperature of the mixer to 130 - 150 °C, adjust the rotation speed to the third high speed, add the titanium alloy fine powder with the second particle size in two portions, and introduce an argon pulse after each addition to embed the titanium alloy fine powder into the gaps of the titanium alloy coarse powder. Mix until the glossiness of the feed surface reaches the preset GU value; S25. Lower the temperature of the mixer to 100 - 120 °C, add the titanium alloy nanopowder with a third particle size of 0.5 - 1 μm at the fourth ultra - high speed synchronously, apply ultrasonic vibration with a frequency of 10 - 15 kHz, and continuously mix until the microscopic observation of the feed cross - section shows that the nanopowder is dispersed to the preset uniformity CV value; S26. Under nitrogen protection, cool the mixed feed to 60 - 80 °C at a rate of 2 °C / min, and monitor the viscosity change in real time during this period. Terminate the cooling when the viscosity reaches the preset viscosity value to obtain a uniform feed with a gradient structure.

[0011] Optionally, step S3 specifically includes the following steps: S31. Heat - treat the mold with a preset shape, and spray a nano - boron nitride - based release agent on the surface of the mold cavity to form a lubricating isolation layer with a preset thickness; S32. Add the obtained uniform feed into the barrel of a micro - screw injection molding machine, and push the feed in three stages under preset injection conditions. The injection pressure increases in each stage, and a constant pressure is applied during the holding pressure stage for 10 - 15 seconds to complete the filling of the mold; S33. Apply a composite - frequency vibration synchronously during the holding pressure stage. First, use high - frequency vibration to eliminate the internal bubbles of the feed, and then switch to low - frequency vibration to directionally control the pore distribution; S34. Perform three - step cooling through the micro - channel circulation system inside the mold. In the first stage, cool it to 80 - 90 °C at a rate of 15 °C / min, in the second stage, cool it to 60 - 70 °C at a rate of 5 °C / min, and in the third stage, cool it naturally to below 40 °C to obtain a stable green body with a qualified dimensional shrinkage rate. S35. Introduce a nitrogen gas flow at a temperature of 40 - 50 °C at the mold parting surface, and use the gas film lubrication effect to separate the green body from the mold cavity. Control the demolding force within the range of 0.5 - 1.2 MPa to obtain a green body with a multi - level connected pore structure.

[0012] Optionally, step S4 specifically includes the following steps: S41. Place the green body in a vacuum drying oven, heat it at a rate of 3 - 5 °C / min to 80 - 100 °C, and keep it at a constant temperature for 1 - 2 hours to eliminate internal stress, obtaining a pre - stabilized green body; S42. Place the pre - stabilized green body into a high - pressure autoclave, inject supercritical CO2 fluid, and control the pressure at 25 - 30 MPa and the temperature at 75 - 85 °C. Perform pulse pressure fluctuation cycling extraction for 40 - 60 minutes to preferentially remove the plasticizer component and the soluble sacrificial template material, forming a primary degreased green body; S43. Transfer the primary degreased green body to a microwave reaction cavity, introduce water vapor as a catalyst carrier, and apply microwave in two stages: first, irradiate with 800 W, 2.45 GHz microwave for 30 minutes to decompose the main binder, and then switch to 1200 W, 5.8 GHz high - frequency microwave to irradiate for 20 minutes to remove the residual binder; S44. Under vacuum conditions, perform staged multi - component gas - phase collaborative cleaning on the green body in sequence; S45. Place the cleaned green body in an argon environment, cool it to room temperature at a rate of 10 - 15 °C / min, and simultaneously apply a 0.1 - 0.3 T steady magnetic field to inhibit pore shrinkage, obtaining a degreased green body with qualified porosity, pore size distribution, and pore connectivity.

[0013] Optionally, step S44 specifically includes: S441. First stage: Introduce 0.1 - 0.3 mol / L hydrochloric acid vapor and treat it at a temperature of 110 - 120 °C for 15 - 20 minutes to dissolve the metal oxide residue; S442. Second stage: Switch to 0.5 - 1 mol / L ammonia water vapor and neutralize the acidic residue at a temperature of 90 - 100 °C for 10 - 15 minutes.

[0014] Optionally, step S5 specifically includes the following steps: S51. Place the degreased green body in a vacuum sintering furnace, heat it at a rate of 8 - 10 °C / min to 750 - 850 °C, introduce an argon - hydrogen gas mixture, and perform constant - temperature sintering for 1 - 1.5 hours to form a pre - sintered green body; S52. Introduce a nitrogen - ammonia gas mixture with a volume ratio of 3:1 into the furnace, apply radio - frequency plasma, and use a multi - axis rotating carrier table to uniformly etch the surface of the degreased green body in all directions for 20 - 30 minutes to form a nitriding activation layer; S53. Heat it up to 1300 - 1350 °C at a rate of 15 - 20 °C / min, simultaneously apply a pulsed electric field with a preset frequency, and keep it warm for 2 - 3 hours to complete densification sintering, so that the relative density reaches the preset densification range; S54. Magnetic field-assisted gradient cooling: After turning off the heating power supply, apply an axial steady magnetic field of 0.5 - 1 T around the sintered body, cool it at a rate of 5 - 8 °C / min to below 600 °C, and then switch to natural cooling to room temperature to obtain a finished titanium alloy implant with qualified grain size and surface roughness.

[0015] The present invention also provides a titanium alloy feed implant, which is prepared by using the preparation method of the titanium alloy feed implant as described above. The titanium alloy feed implant specifically includes a titanium alloy matrix, on the surface of which a biocompatible nitriding activation layer is covered, and a multi-stage connected pore structure is arranged through the titanium alloy matrix; Among them, the interior of the titanium alloy matrix has a gradient grain boundary network composed of nano-grains and sub-micron grains.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Firstly, through the activation treatment of the biodegradable binder system in an inert gas environment, an expanded binder precursor is formed. The activation pretreatment significantly improves the interfacial bonding force between the titanium powder and the binder. Then, the titanium alloy powder with graded ratio and the precursor are mixed in stages in a multi-stage mixing device, and the operations of low-temperature activation, melting and dispersion are sequentially performed to obtain a uniform feed; after the feed is injection-molded with vibration assistance to generate a green body with a multi-stage pore structure, while ensuring the fluidity of the feed, the bionic pore structure is accurately maintained; the binder is gradually removed by the synergistic debinding process of supercritical fluid extraction, microwave decomposition and gas-phase cleaning while retaining the pores. The multi-stage debinding process improves the debinding efficiency through the synergistic effect of supercritical fluid and microwave catalysis and avoids pore collapse; the densification sintering and forming of the titanium alloy implant are realized through pre-sintering and plasma activation treatment; through the coupling design of the innovation of the biodegradable binder system and the intelligent debinding process, on the premise of ensuring the biological safety of the titanium alloy implant, the precise forming of the complex pore structure and the control of sintering densification are realized synchronously. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] The structures, proportions, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions under which the present invention can be implemented. Therefore, they do not have substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention.

[0019] Figure 1 It is one of the process schematic diagrams of the preparation method of the titanium alloy feed implant for the first embodiment; Figure 2 It is the second of the process schematic diagrams of the preparation method of the titanium alloy feed implant for the first embodiment; Figure 3 It is the third of the process schematic diagrams of the preparation method of the titanium alloy feed implant for the first embodiment. Specific embodiments

[0020] In order to make the object, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediate component present at the same time.

[0022] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments.

[0023] Embodiment 1: Combined with Figures 1 to 3 As shown, the embodiment of the present invention provides a preparation method of a titanium alloy feed implant, including the following steps: S1, placing a biodegradable bonding system containing a main binder, a plasticizer, and a sacrificial template material in an inert gas environment for activation treatment to form a swollen binder precursor; By activating the biodegradable binder system (main binder, plasticizer, sacrificial template) in an inert gas environment, the physical and chemical states of the binder components are regulated. The inert gas environment can prevent the oxidation and deterioration of organic components. The activation treatment prompts the sacrificial template material to absorb moisture and expand, forming open pore channels, providing a binder precursor with a high specific surface area for the subsequent mixing stage. The core of this step lies in pre-constructing the pore generation basis of the feed through the synergistic effect of the binder and the template.

[0024] S2, Mix the titanium alloy powder with the expanded binder precursor in a multi-stage mixing device according to a preset particle size ratio, and sequentially perform low-temperature activation, medium-temperature melting, and high-speed dispersion operations to obtain a uniform feed. A multi-stage mixing device is used to perform low-temperature activation, medium-temperature melting, and high-speed dispersion operations in stages. In the low-temperature activation stage, gentle heating is used to initially bond the binder and titanium powder, avoiding nanopowder agglomeration. In the medium-temperature melting stage, sufficient wetting of the binder and powder is achieved. In the high-speed dispersion stage, mechanical shear force is used to break the interparticle forces to ensure the uniformity of the feed. The staged mixing strategy effectively balances the contradictions among the fluidity, dispersibility of titanium powder, and the coating property of the binder.

[0025] S3, Inject the prepared uniform feed into a mold with a preset shape, and complete injection molding under vibration assistance to obtain a green body with a multi-level pore structure. The feed is transformed into a green body with a multi-level pore structure through vibration-assisted injection molding. Vibration energy eliminates internal bubbles during the injection process and simultaneously guides the directional distribution of the sacrificial template in the feed, forming a composite structure of through macroscopic pores and micron-scale pores. The preset shape of the mold directly determines the geometric accuracy of the implant, while the regulation of vibration parameters directly affects the uniformity of pore distribution.

[0026] S4, Perform multi-stage debinding on the obtained green body, sequentially using supercritical fluid extraction, microwave catalytic decomposition, and gas-phase cleaning processes to gradually remove the binder components and retain the pore structure, forming a debound body. Through a multi-stage debinding process of supercritical fluid extraction, microwave catalytic decomposition, and gas-phase cleaning, the binder system is gradually removed. Supercritical fluid preferentially extracts low-molecular-weight plasticizers and sacrificial templates, microwave catalytic decomposition decomposes the main binder, and gas-phase cleaning removes residues. The key to this step lies in the synergistic effect of each debinding method: supercritical fluid avoids pore collapse, microwave decomposition improves debinding efficiency, and gas-phase cleaning ensures the complete removal of chemical residues.

[0027] S5, Place the debound body in a vacuum sintering furnace, first perform pre-sintering treatment, then introduce reactive plasma for surface activation, and complete densification sintering at high temperature to obtain the finished titanium alloy implant.

[0028] The densification of the implant is achieved through a three-stage treatment of pre-sintering, plasma activation, and high-temperature sintering. Pre-sintering eliminates internal defects in the debound body and stabilizes the structure; plasma activation constructs a nanoscale rough layer on the surface to enhance biocompatibility; high-temperature sintering realizes grain rearrangement densification through atomic diffusion. The innovation of this step lies in the organic combination of the surface modification process and densification sintering, synchronously improving the mechanical properties and biological properties of the implant.

[0029] The working principle of the present invention is as follows: First, an expanded binder precursor is formed through the activation treatment of a biodegradable binder system in an inert gas environment. The activation pretreatment significantly improves the interfacial bonding force between the titanium powder and the binder. Then, the graded titanium alloy powder and the precursor are mixed in stages in a multi-stage mixing device, and low-temperature activation, melting, and dispersion operations are sequentially performed to obtain a uniform feedstock. After the feedstock is injection-molded with vibration assistance to generate a green body with a multi-level pore structure, while ensuring the fluidity of the feedstock, the bionic pore structure is accurately maintained; a synergistic debinding process of supercritical fluid extraction, microwave decomposition, and gas-phase cleaning is used to gradually remove the binder and retain the pores. The multi-stage debinding process improves the debinding efficiency through the synergistic effect of supercritical fluid and microwave catalysis and avoids pore collapse; the densification sintering of the titanium alloy implant is realized through pre-sintering and plasma activation treatment; through the coupling design of the innovation of the biodegradable binder system and the intelligent debinding process, on the premise of ensuring the biological safety of the titanium alloy implant, the precise forming of the complex pore structure and the control of sintering densification are synchronously achieved.

[0030] In this embodiment, further description is as follows. The biodegradable binder system includes: The main binder is a biodegradable polyester, selected from at least one of polylactic acid, polycaprolactone, and polyglycolic acid, accounting for 35 - 45 wt% of the total mass of the binder system; The main binder is selected as a biodegradable polyester (such as polylactic acid, polycaprolactone, etc.), ensuring the biological safety of the implant while providing the bonding strength required for forming; the proportion of 35 - 45 wt% of the main binder avoids the difficulty of debinding caused by excessive amount while ensuring the strength of the feedstock.

[0031] The plasticizer is a biocompatible ester compound, selected from at least one of citrate ester, acetyl citrate ester, and polyethylene glycol, accounting for 10 - 20 wt% of the total mass of the binder system.

[0032] The plasticizer uses a biocompatible ester compound (such as citrate ester), improving the processing fluidity by reducing the glass transition temperature of the binder; The sacrificial template material is a swellable biopolymer, selected from at least one of alginate, gelatin, and starch-based porous microspheres, accounting for 3 - 8 wt% of the total mass of the binder system.

[0033] The sacrificial template material (such as alginate) constructs pore generation sites through adjustable swelling characteristics, and a 3-8 wt% sacrificial template content achieves a balance between porosity requirements and green body mechanical properties.

[0034] In this embodiment, it is further illustrated that the sum of the mass fractions of the components in the binder system is 80-95 wt%, and the balance is processing aids. The introduction of processing aids can optimize the powder dispersibility (such as zinc stearate improving fluidity) and demolding performance (such as polyethylene wax reducing the friction coefficient) during the mixing process, and its dosage is dynamically adjusted according to specific process requirements.

[0035] In this embodiment, it is specifically illustrated that step S1 specifically includes the following steps: S11, Mix the main binder particles and the plasticizer in a preset ratio and place them in a vacuum drying oven. Dry them at 80-100 °C for 2-4 hours to remove adsorbed moisture and volatile impurities, and obtain a pretreated binder mixture; The purpose of vacuum drying the mixture of the main binder and the plasticizer is to remove the adsorbed moisture and volatile impurities of the material, ensuring the purity and stability of the binder system. The drying temperature range of 80-100 °C can not only effectively promote the evaporation of moisture but also avoid thermal degradation of the polyester-based main binder; the treatment time of 2-4 hours balances the drying efficiency and energy consumption control. The vacuum environment can prevent the oxidation of organic components at high temperatures and at the same time enhance the mass transfer efficiency.

[0036] S12, Transfer the pretreated binder mixture to a closed reaction kettle, introduce nitrogen to displace air, and then heat it up to 60-80 °C at a rate of 5-8 °C / min and keep it at a constant temperature for 30-60 minutes to allow the plasticizer to penetrate into the molecular chain gaps of the main binder and form a pre-swollen complex; Gradient heating activation is carried out in an inert gas environment, and the core is to achieve molecular-level binding between the plasticizer and the main binder. The operation of displacing air with nitrogen eliminates the oxidation risk of oxygen to organic components. The heating rate of 5-8 °C / min ensures that the plasticizer gradually penetrates into the molecular chain gaps of the main binder, avoiding local overheating or phase separation caused by rapid heating. The constant temperature range of 60-80 °C is selected based on the glass transition temperature (Tg) range of polyester-based materials, which can not only promote the diffusion of the plasticizer but also prevent the premature melting of the binder. The constant temperature time of 30-60 minutes allows the plasticizer to complete full penetration and form a uniform pre-swollen complex, laying a structural foundation for subsequent pore construction.

[0037] S13, Add the sacrificial template material to the pre-swollen complex, apply ultrasonic vibration for 10-20 minutes under nitrogen protection, so that the sacrificial template material is evenly dispersed and embedded in the main binder network structure to form a porous precursor substrate; The sacrificial template material is embedded in the binder network through ultrasonic-assisted dispersion. A nitrogen protection environment maintains the chemical inertness of the material and prevents oxidation reactions caused by ultrasonic cavitation effects. An ultrasonic frequency of 20 - 40 kHz generates high-intensity cavitation bubbles, which use the impact force of microjets to break up the agglomerates of the sacrificial template, achieving uniform dispersion at the nano- to micron-scale. An action time of 10 - 20 minutes ensures sufficient dispersion without damaging the molecular chain structure of the binder. The synergistic effect of ultrasonic energy and mechanical dispersion enables the sacrificial template to be precisely positioned in the weak areas of the binder network, forming controllable pore generation sites.

[0038] S14, Place the porous precursor substrate in a nitrogen environment with a humidity of 80 - 90% and let it stand for 8 - 12 hours, and control the temperature fluctuation range (±2 °C) to allow the sacrificial template material to absorb moisture and expand to 120 - 150% of its original volume, obtaining a swollen binder precursor with open pore channels.

[0039] Controlled swelling of the sacrificial template is achieved through humidity regulation to construct open pore channels. A humidity environment of 80 - 90% provides sufficient water molecules to drive the swelling of sacrificial templates such as alginate, and a volume expansion rate range of 120 - 150% ensures pore connectivity without damaging the binder skeleton. A temperature fluctuation control of ±2 °C suppresses the interference of humidity fluctuations on the swelling rate.

[0040] In this embodiment, specifically, step S2 specifically includes the following steps: S21, Place the titanium alloy powder with a preset particle size ratio in a vacuum drying oven and dry it at 120 - 150 °C for 1 - 2 hours to remove the surface adsorbed moisture and obtain activated titanium powder; The titanium alloy powder is pretreated by vacuum drying to eliminate the interference of surface adsorbed moisture on the subsequent mixing process. The drying temperature range of 120 - 150 °C can not only efficiently remove moisture (titanium powder has a large specific surface area and is prone to moisture absorption), but also avoid oxidation or sintering of the titanium powder due to excessive temperature; the drying time of 1 - 2 hours balances the dehydration efficiency and energy consumption control. The vacuum environment can block the oxidation of titanium powder by oxygen and at the same time accelerate the kinetic process of water evaporation.

[0041] S22, Add the swollen binder precursor to a double planetary mixer, control the mixing temperature at 80 - 100 °C, and mix at a first low speed for 10 - 15 minutes to form a viscoelastic matrix; The preliminary plasticization of the binder matrix is achieved in a twin-planet mixer. The mixing temperature of 80 - 100 °C is selected based on the melting temperature range of the biodegradable polyester, which can soften the binder without causing thermal decomposition. The first low-speed (20 - 30 rpm) mixing strategy promotes the uniform coating of the binder on the mixing blades through gentle shear force, forming a continuous viscoelastic matrix. The action time of 10 - 15 minutes ensures the completion of the melting and reorganization of the binder, while avoiding the molecular chain breakage caused by long-term high temperature.

[0042] S23, Add titanium alloy coarse powder with the first particle size of 15 - 25 μm to the viscoelastic matrix in three portions, with an interval of 5 - 8 minutes between each addition. The mixing temperature is maintained at 80 - 100 °C, and the rotation speed is increased to the second medium speed. After each powder addition, continue mixing until the preset torque fluctuation range is reached to form a primary composite feedstock. Adopt the strategy of adding titanium alloy coarse powder (15 - 25 μm) in stages, and achieve the uniform dispersion of the coarse powder by dynamically adjusting the mixing parameters. The design of adding powder in three portions (with an interval of 5 - 8 minutes between each addition) is based on the powder packing density theory to avoid the bridging phenomenon caused by one-time addition. Maintaining the mixing temperature at 80 - 100 °C can keep the viscosity stability of the binder, and the shear force of the second medium speed (40 - 50 rpm) effectively breaks the coarse powder agglomerates. The torque fluctuation range (such as ±5 N·m) is used as the criterion for mixing homogenization, and the mixing time is adjusted through real-time feedback.

[0043] S24, Raise the temperature of the mixer to 130 - 150 °C, adjust the rotation speed to the third high speed, and add titanium alloy fine powder with the second particle size of 5 - 8 μm in two portions. After each addition, introduce an argon pulse (pressure 0.3 - 0.5 MPa, duration 30 s) to embed the titanium alloy fine powder into the gaps of the titanium alloy coarse powder, and mix until the glossiness GU value of the feedstock surface reaches the preset value. Precise filling of the fine powder (5 - 8 μm) is achieved through the synergistic effect of high-temperature mixing and argon pulse. The mixing temperature of 130 - 150 °C reduces the viscosity of the binder and promotes the penetration of the fine powder into the gaps of the coarse powder. The third high speed (60 - 80 rpm) enhances the convective mixing efficiency, and the argon pulse (0.3 - 0.5 MPa / 30 s) uses the gas impact force to break the soft agglomerates of the fine powder. The surface glossiness GU value (≥85) is used as a visual index of mixing uniformity, reflecting the interfacial bonding state between the fine powder and the coarse powder.

[0044] S25, Cool the mixer to 100 - 120 °C, synchronously add titanium alloy nano powder with the third particle size of 0.5 - 1 μm at the fourth ultra-high speed, apply ultrasonic vibration with a frequency of 10 - 15 kHz, and continue mixing until the microscopic observation of the feedstock cross-section shows that the nano powder is dispersed to the preset uniformity CV value. Adopt the strategy of synergistic dispersion of low-temperature mixing and ultrasonic waves to overcome the dispersion problem of nano-powders (0.5 - 1μm). The mixing temperature of 100 - 120°C inhibits the thermal migration and agglomeration of nano-powders while maintaining the fluidity of the binder; the fourth ultra-high rotation speed (100 - 120 rpm) combined with ultrasonic vibration of 10 - 15 kHz realizes the single-particle-level dispersion of nano-powders through the coupling effect of mechanical shearing and acoustic cavitation. The cross-sectional microscopic uniformity CV value (<3%) is used as a quantitative standard to ensure the formation of a reinforcing phase network of nano-powders in the feedstock.

[0045] S26, Under nitrogen protection, cool the mixed feedstock to 60 - 80°C at a rate of 2°C / min, and monitor the viscosity change in real time during this period. When the viscosity reaches the preset viscosity value, terminate the cooling to obtain a uniform feedstock with a gradient structure.

[0046] Precisely control the rheological properties of the feedstock through programmed cooling and real-time viscosity monitoring. The cooling rate of 2°C / min matches the crystallization kinetic characteristics of the binder, avoiding internal stress concentration caused by rapid cooling; the nitrogen protection environment prevents the surface of the feedstock from oxidizing and forming a crust. The preset viscosity value (2800 ± 200 Pa·s) is set based on the rheological requirements of the injection molding process, and closed-loop control is achieved through an on-line viscosity sensor.

[0047] In this embodiment, specifically, step S3 specifically includes the following steps: S31, Heat-treat the mold with a preset shape, and spray a nano-boron nitride-based mold release agent on the surface of the mold cavity to form a lubricating isolation layer with a preset thickness; Optimize the injection molding conditions through mold preheating and surface treatment. Heating the mold to 120 - 150°C can reduce the temperature difference between the feedstock and the mold cavity, inhibiting surface defects caused by rapid cooling; the spraying of the nano-boron nitride-based mold release agent (thickness 5 - 8μm) utilizes its high lubricity and high-temperature resistance characteristics to form a stable lubricating film during the injection process, reducing the demolding resistance and protecting the microstructure of the green body surface. By balancing the heat conduction efficiency and the interface lubrication requirements, it provides a basis for accurately reproducing the preset pore structure, and at the same time avoids the problem of residual pollution of pores by traditional mold release agents.

[0048] S32, Add the obtained uniform feedstock to the barrel of a micro-screw injection molding machine, and advance the feedstock in three stages under the preset injection conditions with a screw speed of 20 - 30 rpm and an injection pressure of 80 - 100 MPa. The injection pressure increases in each stage, and a constant pressure is applied during the holding pressure stage for 10 - 15 seconds to complete the filling of the mold cavity; An efficient filling of the feedstock is achieved by adopting a multi-stage pressure injection strategy. The combination of a screw speed of 20 - 30 rpm and an injection pressure of 80 - 100 MPa ensures the uniform advancement of the feedstock. The three-stage pressure increase (such as 80 → 100 → 120 MPa) gradually compacts the feedstock through gradient boosting, reducing defects such as jetting marks at the flow front. A constant pressure (such as 100 MPa) during the holding pressure stage maintains the densification of the feedstock, and a filling time of 10 - 15 seconds matches the curing kinetics of the feedstock.

[0049] S33, Apply a composite frequency vibration synchronously during the holding pressure stage. First, use a high-frequency vibration of 10 - 15 kHz to eliminate internal bubbles in the feedstock, and then switch to a low-frequency vibration of 50 - 100 Hz to directionally regulate the pore distribution. The vibration acceleration is controlled within the range of 5 - 8g; Active regulation of the pore structure is achieved through composite frequency vibration. The 10 - 15 kHz high-frequency vibration uses the cavitation effect to eliminate internal bubbles in the feedstock, avoiding pore blockage; switching to the 50 - 100 Hz low-frequency vibration directionally guides the migration of the sacrificial template through mechanical waves to form a preset pore distribution pattern. The range setting of the vibration acceleration of 5 - 8g can not only effectively drive the movement of the template but also avoid damage to the green body structure caused by excessive vibration.

[0050] S34, Execute three-step cooling through the microchannel circulation system built into the mold. In the first stage, cool at a rate of 15 °C / min to 80 - 90 °C, in the second stage, cool at a rate of 5 °C / min to 60 - 70 °C, and in the third stage, naturally cool to below 40 °C to obtain a stable green body with a qualified dimensional shrinkage rate; Control the dimensional stability of the green body through a gradient cooling strategy. In the first stage, rapid cooling at 15 °C / min locks the pore structure; in the second stage, slow cooling at 5 °C / min reduces the internal stress caused by the sudden temperature drop; in the third stage, natural cooling avoids local deformation caused by forced cooling. The temperature nodes of the three-step cooling (80 - 90 °C → 60 - 70 °C → 40 °C) match the temperature range of the binder phase change, and the parameter design with a dimensional shrinkage rate ≤ 0.2% ensures that the geometric accuracy of the green body meets the tolerance requirements of medical implants.

[0051] S35, Introduce a nitrogen gas flow at a temperature of 40 - 50 °C at the mold parting surface, and use the gas film lubrication effect to separate the green body from the mold cavity. The demolding force is controlled within the range of 0.5 - 1.2 MPa to obtain a green body with a multi-stage connected pore structure.

[0052] Non-destructive demolding is achieved by using the gas film lubrication effect. The 40 - 50 °C nitrogen gas flow (flow rate 2 - 3 m / s) forms a gas film layer of 0.1 - 0.3 mm between the mold cavity and the green body, protecting the integrity of the pore structure by reducing the contact friction force (demolding force 0.5 - 1.2 MPa). The temperature is set slightly higher than the glass transition temperature of the green body to ensure that the green body has an appropriate elastic deformation ability during demolding.

[0053] In this embodiment, specifically, step S4 specifically includes the following steps: S41. Place the green body in a vacuum drying oven and heat it at a rate of 3 - 5 °C / min to 80 - 100 °C, and keep it at a constant temperature for 1 - 2 hours to eliminate internal stress, obtaining a pre-stabilized green body; Pre-treat the green body through vacuum drying and gradient heating to create a stable basis for subsequent debinding. The heating rate of 3 - 5 °C / min avoids microcracks caused by sudden changes in thermal stress. Keeping at a constant temperature of 80 - 100 °C for 1 - 2 hours promotes the relaxation of the binder molecular chains and releases the molding residual stress. The vacuum environment blocks the oxidation reaction and at the same time accelerates the discharge of low-molecular volatiles. By matching the (temperature - time - vacuum degree) with the thermodynamic characteristics of the green body, both structural defects are eliminated and pore deformation is not caused, ensuring that the green body in the debinding process has a uniform mechanical state.

[0054] S42. Place the pre-stabilized green body into a high-pressure reactor, inject supercritical CO2 fluid, and control the pressure at 25 - 30 MPa and the temperature at 75 - 85 °C, and extract with a pulsed pressure fluctuation cycle for 40 - 60 minutes to preferentially remove the plasticizer components and soluble sacrificial template materials, forming a primary debound green body; Adopt the supercritical CO2 fluid pulsed extraction technology to preferentially remove the plasticizer and sacrificial template. The combination of a pressure of 25 - 30 MPa and a temperature of 75 - 85 °C makes CO2 reach the supercritical state, which has both the high diffusivity of a gas and the strong solubility of a liquid; the pulsed pressure fluctuation (±5 MPa / 10 s) strengthens the mass transfer efficiency through the periodic compression - expansion effect, increasing the dissolution rate of the binder by about 30%. The action time of 40 - 60 minutes matches the extraction kinetic requirements, fully removing the low-molecular components while avoiding pore structure fatigue damage caused by long-term high pressure.

[0055] S43. Transfer the primary debound green body to a microwave reaction cavity, introduce water vapor as a catalyst carrier, and apply microwaves in two stages: first, irradiate with 800 W, 2.45 GHz microwaves for 30 minutes to decompose the main binder, and then switch to 1200 W, 5.8 GHz high-frequency microwaves to irradiate for 20 minutes to remove the residual binder; Achieve efficient removal of the binder through dual-frequency microwave catalytic decomposition. The 800 W, 2.45 GHz microwaves penetrate the entire green body, triggering the molecular resonance cleavage of the main binder (such as PLA); switching to 1200 W, 5.8 GHz high-frequency microwaves targets the local residues for fixed-point removal, and the high-frequency electromagnetic field focusing effect improves the energy utilization rate. Water vapor (0.5 - 1 L / min) acts as a catalyst to accelerate the oxidation decomposition of organic substances through hydroxyl radicals. The two-stage irradiation design of 30 + 20 minutes is based on the decomposition activation energy differences of different binder components, and the parameter settings (power - frequency - time) achieve the distribution of energy input, avoiding matrix oxidation caused by overheating.

[0056] S44. Perform staged multi-component gas-phase collaborative cleaning on the green body under vacuum conditions. Specifically, it includes: S441. First stage: Introduce hydrochloric acid vapor with a concentration of 0.1 - 0.3 mol / L and treat it at a temperature of 110 - 120 °C for 15 - 20 minutes to dissolve the residual metal oxides. S442. Second stage: Switch to ammonia water vapor with a concentration of 0.5 - 1 mol / L and neutralize the acidic residues at a temperature of 90 - 100 °C for 10 - 15 minutes.

[0057] The vacuum environment enhances the mass transfer efficiency of gas-solid reactions. The staged treatment (15 + 10 minutes) ensures complete chemical reactions and does not corrode the titanium substrate.

[0058] S45. Place the cleaned green body in an argon environment and cool it to room temperature at a rate of 10 - 15 °C / min. Synchronously apply a steady magnetic field of 0.1 - 0.3 T to inhibit pore shrinkage and obtain a debound green body with qualified porosity, pore size distribution, and pore connectivity.

[0059] The pore structure of the debound green body is locked by magnetic field-assisted cooling. The cooling rate of 10 - 15 °C / min inhibits the lattice distortion caused by rapid phase transformation. The steady magnetic field of 0.1 - 0.3 T uses the Lorentz force to restrain the migration of metal atoms, reducing the pore shrinkage rate from 3.2% to less than 0.5%. The argon environment prevents the oxidation of the high-temperature green body and simultaneously achieves rapid cooling and surface passivation. The parameter settings of this step (cooling rate - magnetic field strength - gas atmosphere) enable the final green body to meet the implant design requirements in terms of porosity (55 - 70%), pore size distribution, and connectivity (≥90%) through the coupling effect of multiple physical fields.

[0060] In this embodiment, specifically, step S5 includes the following steps: S51. Place the debound green body in a vacuum sintering furnace and heat it to 750 - 850 °C at a rate of 8 - 10 °C / min. Introduce a mixed gas of argon and hydrogen (volume ratio 9:1, flow rate 5 - 8 L / min) and perform isothermal sintering for 1 - 1.5 hours to form a pre-sintered green body. The preliminary densification of the debound green body and oxygen content control are achieved through gradient pre-sintering. The heating rate of 8 - 10 °C / min matches the phase transformation kinetics of the titanium alloy, avoiding the grain boundary stress concentration caused by rapid heating. The reducing atmosphere of the argon-hydrogen mixed gas (9:1 volume ratio) effectively inhibits the oxidation of the titanium substrate, and the infiltration of hydrogen can reduce trace surface oxides (such as TiO2). The flow rate of 5 - 8 L / min ensures uniform furnace atmosphere, and the 1 - 1.5 hours of isothermal sintering enables the green body to form preliminary sintering neck connections, providing a pre-sintered green body with stable structure for subsequent activation treatment.

[0061] S52. Introduce a nitrogen-ammonia mixed gas with a volume ratio of 3:1 into the furnace, apply radio frequency plasma, and uniformly etch the surface of the degreased green body for 20 - 30 minutes through a multi-axis rotating carrier stage to form a nitrided activation layer. Construct a bioactive surface through multi-axis rotating plasma etching. The nitrogen-ammonia mixed gas (volume ratio 3:1) generates highly reactive nitrogen radicals under the action of radio frequency plasma (4 - 6 kW), and reacts with the titanium surface to form a TiN / TiON composite nitride layer; the multi-axis rotating carrier stage ensures uniform etching in all directions of the complex three-dimensional structure, and the 20 - 30 minute treatment time matches the growth kinetics requirements of the nitride layer.

[0062] S53. Heat up to 1300 - 1350 °C at a rate of 15 - 20 °C / min, synchronously apply a pulsed electric field with a preset frequency, and keep warm for 2 - 3 hours to complete densification sintering, so that the relative density reaches the preset densification range. Realize the final densification of the titanium alloy by pulsed electric field-assisted sintering. The heating rate of 15 - 20 °C / min balances the sintering efficiency and the control of thermal stress; the pulsed electric field of 0.1 - 0.5 Hz (50 - 80 A / cm²) drives grain boundary migration through a periodic strong electric field, accelerating pore closure (the porosity drops from 15% to less than 0.5%). The sintering temperature of 1300 - 1350 °C and the holding time of 2 - 3 hours match the α→β phase transformation temperature range of the titanium alloy (the proportion of the β phase > 95%), making the grain size refined to less than 20 μm.

[0063] S54. Magnetic field-assisted gradient cooling: After turning off the heating power supply, apply an axial steady magnetic field of 0.5 - 1 T around the sintered body, cool it at a rate of 5 - 8 °C / min to below 600 °C, and then switch to natural cooling to room temperature to obtain a finished titanium alloy implant with qualified grain size and surface roughness.

[0064] Optimize the microstructure and mechanical properties of the titanium alloy through magnetic field-controlled cooling. The axial steady magnetic field of 0.5 - 1 T generates a Lorentz force during the cooling process, inhibiting the abnormal growth of β-phase grains (grain size ≤ 20 μm); the gradient cooling rate of 5 - 8 °C / min matches the martensitic transformation kinetics, avoiding the accumulation of residual stress caused by rapid cooling (< 50 MPa). Switching to natural cooling below 600 °C can retain the metastable α' phase, endowing the implant with high strength and toughness (yield strength ≥ 950 MPa).

[0065] Example Two: The present invention also provides a titanium alloy feed implant, which is prepared by using the preparation method of the titanium alloy feed implant in Example One. The titanium alloy feed implant specifically includes a titanium alloy matrix, on the surface of which there is a biocompatible nitrided activation layer, and a multi-stage connected pore structure is arranged through the titanium alloy matrix; wherein, the interior of the titanium alloy matrix has a gradient grain boundary network composed of nano-grains and sub-micron grains.

[0066] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A preparation method of a titanium alloy feed implant, characterized in that, It includes the following steps: S1. Place the biodegradable binder system containing a main binder, a plasticizer, and a sacrificial template material in an inert gas environment for activation treatment to form a swollen binder precursor; S2. Mix the titanium alloy powder with the preset particle size ratio and the swollen binder precursor in a multi-stage mixing device in stages, and sequentially perform low-temperature activation, medium-temperature melting, and high-speed dispersion operations to obtain a uniform feedstock; S3. Inject the prepared uniform feedstock into a mold with a preset shape, and complete injection molding under vibration assistance to obtain a green body with a multi-level pore structure; S4. Perform multi-stage debinding on the obtained green body, and sequentially use supercritical fluid extraction, microwave catalytic decomposition, and gas-phase cleaning processes to gradually remove the binder components and retain the pore structure to form a debound body; S5. Place the debound body in a vacuum sintering furnace, first perform pre-sintering treatment, then introduce a reactive plasma for surface activation, and complete densification sintering at high temperature to obtain a finished titanium alloy implant.

2. The preparation method of the titanium alloy feed implant according to claim 1, characterized in that The biodegradable binder system includes: The main binder is a biodegradable polyester, selected from at least one of polylactic acid, polycaprolactone, and polyglycolic acid, accounting for 35-45 wt% of the total mass of the binder system; The plasticizer is a biocompatible ester compound, selected from at least one of citrate esters, acetyl citrate esters, and polyethylene glycols, accounting for 10-20 wt% of the total mass of the binder system; The sacrificial template material is a swellable biopolymer, selected from at least one of alginate, gelatin, and starch-based porous microspheres, accounting for 3-8 wt% of the total mass of the binder system.

3. The preparation method of the titanium alloy feed implant according to claim 2, characterized in that, The sum of the mass fractions of the components of the binder system is 80-95 wt%, and the balance is a processing aid.

4. The preparation method of the titanium alloy feed implant according to claim 1, characterized in that, The specific steps of step S1 include the following steps: S11. Mix the main binder particles and the plasticizer in a preset ratio and place them in a vacuum drying oven, and dry them at 80-100 °C for 2-4 hours to remove adsorbed moisture and volatile impurities to obtain a pretreated binder mixture; S12. Transfer the pretreated binder mixture to a closed reaction kettle, introduce nitrogen to displace air, and then heat it at a rate of 5-8 °C / min to 60-80 °C and keep it at a constant temperature for 30-60 minutes to allow the plasticizer to penetrate into the molecular chain gaps of the main binder to form a pre-swollen complex; S13. Add the sacrificial template material to the pre-swollen complex, and apply ultrasonic vibration for 10-20 minutes under nitrogen protection to uniformly disperse the sacrificial template material and embed it in the main binder network structure to form a porous precursor substrate; S14. Place the porous precursor substrate in a nitrogen environment with a humidity of 80-90% and let it stand for 8-12 hours, and control the temperature fluctuation range to make the sacrificial template material absorb moisture and swell to 120-150% of its original volume to obtain a swollen binder precursor with open pore channels.

5. The preparation method of the titanium alloy feed implant according to claim 1, characterized in that, The specific steps of step S2 include the following steps: S21. Place the titanium alloy powder with a preset particle size ratio in a vacuum drying oven, and dry it at 120-150 °C for 1-2 hours to remove the surface adsorbed moisture to obtain activated titanium powder; S22. Add the expanded binder precursor into a twin-planet mixer, control the mixing temperature at 80 - 100 °C, and mix at a first low speed for 10 - 15 minutes to form a viscoelastic matrix; S23. Add titanium alloy coarse powder with the first particle size into the viscoelastic matrix in three portions, with an interval of 5 - 8 minutes between each addition. Maintain the mixing temperature at 80 - 100 °C, increase the speed to a second medium speed, and continuously mix until the preset torque fluctuation range is reached after each powder addition to form a primary composite feedstock; S24. Heat the mixer to 130 - 150 °C, adjust the speed to a third high speed, add titanium alloy fine powder with the second particle size in two portions, and introduce an argon pulse after each addition to embed the titanium alloy fine powder into the gaps of the titanium alloy coarse powder, and mix until the glossiness of the feedstock surface reaches the preset GU value; S25. Cool the mixer to 100 - 120 °C, add titanium alloy nanopowder with a third particle size of 0.5 - 1 μm at the fourth ultra-high speed synchronously, apply ultrasonic vibration with a frequency of 10 - 15 kHz, and continuously mix until the microscopic observation of the feedstock cross-section shows that the nanopowder is dispersed to the preset uniformity CV value; S26. Under nitrogen protection, cool the mixed feedstock at a rate of 2 °C / min to 60 - 80 °C, and monitor the viscosity change in real time during this period. Terminate the cooling when the viscosity reaches the preset viscosity value to obtain a uniform feedstock with a gradient structure.

6. The preparation method of the titanium alloy feed implant according to claim 1, characterized in that, The specific steps of step S3 are as follows: S31. Heat-treat a mold with a preset shape, and spray a nano-boron nitride-based release agent on the surface of the mold cavity to form a lubricating isolation layer with a preset thickness; S32. Add the obtained uniform feedstock into the barrel of a micro-screw injection molding machine, and push the feedstock in three stages under preset injection conditions. The injection pressure increases in each stage, and a constant pressure is applied during the holding pressure stage for 10 - 15 seconds to complete the mold filling; S33. Apply a composite frequency vibration synchronously during the holding pressure stage. First, use high-frequency vibration to eliminate the internal bubbles of the feedstock, and then switch to low-frequency vibration to directionally control the pore distribution; S34. Perform three-step cooling through the micro-channel circulation system inside the mold. In the first stage, cool at a rate of 15 °C / min to 80 - 90 °C, in the second stage, cool at a rate of 5 °C / min to 60 - 70 °C, and in the third stage, naturally cool to below 40 °C to obtain a stable green body with a qualified dimensional shrinkage rate; S35. Introduce a nitrogen gas flow with a temperature of 40 - 50 °C at the mold parting surface, and use the gas film lubrication effect to separate the green body from the mold cavity. Control the demolding force within the range of 0.5 - 1.2 MPa to obtain a green body with a multi-level connected pore structure.

7. The preparation method of the titanium alloy feed implant according to claim 1, characterized in that, The specific steps of step S4 are as follows: S41. Place the green body in a vacuum drying oven, heat it at a rate of 3 - 5 °C / min to 80 - 100 °C, and keep it at a constant temperature for 1 - 2 hours to eliminate internal stress and obtain a pre-stabilized green body; S42. Place the pre-stabilized green body into a high-pressure autoclave, inject supercritical CO2 fluid, and control the pressure at 25 - 30 MPa and the temperature at 75 - 85 °C, and perform pulse pressure fluctuation cycling extraction for 40 - 60 minutes to preferentially remove the plasticizer components and soluble sacrificial template materials to form a primary debound body; S43. Transfer the primary degreased green body to the microwave reaction chamber, introduce water vapor as the catalyst carrier, and apply microwave in two stages: first, irradiate with 800 W, 2.45 GHz microwave for 30 minutes to decompose the main binder, and then switch to 1200 W, 5.8 GHz high-frequency microwave for 20 minutes to remove the residual binder; S44. Under vacuum conditions, perform multi-component gas-phase synergistic cleaning on the green body in stages; S45. Place the cleaned green body in an argon environment, cool it to room temperature at a rate of 10 - 15 °C / min, and simultaneously apply a 0.1 - 0.3 T steady magnetic field to inhibit pore shrinkage, obtaining a degreased green body with qualified porosity, pore size distribution, and pore connectivity.

8. The preparation method of the titanium alloy feed implant according to claim 7, characterized in that, The specific steps of step S44 include: S441. The first stage: Introduce 0.1 - 0.3 mol / L hydrochloric acid vapor and treat it at a temperature of 110 - 120 °C for 15 - 20 minutes to dissolve the metal oxide residue; S442. The second stage: Switch to 0.5 - 1 mol / L ammonia water vapor to neutralize the acidic residue at a temperature of 90 - 100 °C for 10 - 15 minutes.

9. The preparation method of the titanium alloy feed implant according to claim 1, characterized in that, The specific steps of step S5 include the following steps: S51. Place the degreased green body in a vacuum sintering furnace, heat it to 750 - 850 °C at a rate of 8 - 10 °C / min, introduce an argon-hydrogen gas mixture, and perform isothermal sintering for 1 - 1.5 hours to form a pre-sintered green body; S52. Introduce a nitrogen-ammonia gas mixture with a volume ratio of 3:1 into the furnace, apply radio frequency plasma, and uniformly etch the surface of the degreased green body in all directions for 20 - 30 minutes through a multi-axis rotating carrier table to form a nitrided activation layer; S53. Heat it to 1300 - 1350 °C at a rate of 15 - 20 °C / min, simultaneously apply a pulsed electric field with a preset frequency, and keep the temperature for 2 - 3 hours to complete densification sintering, so that the relative density reaches the preset densification range; S54. Magnetic field-assisted gradient cooling: After turning off the heating power, apply an axial steady magnetic field of 0.5 - 1 T around the sintered body, cool it to below 600 °C at a rate of 5 - 8 °C / min, and then switch to natural cooling to room temperature to obtain a finished titanium alloy implant with qualified grain size and surface roughness.

10. A titanium alloy feed implant, characterized in that, Prepared by the method for preparing a titanium alloy feed implant according to any one of claims 1 to 9, the titanium alloy feed implant specifically includes a titanium alloy matrix, the surface of which is covered with a biocompatible nitrided activation layer, and the titanium alloy matrix is provided with a multi-stage connected pore structure; Wherein, the interior of the titanium alloy matrix has a gradient grain boundary network composed of nano-grains and sub-micron grains.

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