A mold and method for preparing a bionic bone radial gradient porous NiTi alloy

Abstract

The present invention discloses a mold and method for preparing a biomimetic bone radial gradient porous NiTi alloy, comprising the following steps: 1) mold design and assembly; 2) slurry preparation; 3) co-injection molding; 4) curing and drying; 5) degreasing and sintering; and 6) pore-forming agent removal. The biomimetic bone radial gradient porous nickel-titanium alloy prepared by the present invention has a relatively continuous porosity variation from 15% in the outer layer to a maximum of 70% in the inner layer, and an average pore size variation from 30 μm in the outer layer to over 400 μm in the inner layer. The mechanical properties are substantially matched to those of bone. The biomimetic bone radial gradient nickel-titanium alloy prepared by the method of the present invention can be used as an ideal artificial bone tissue repair or replacement material, and is suitable for directly preparing materials such as dental implants, artificial joints, and bone trauma products without the need for subsequent processing.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy preparation, and relates to a mold and a method for preparing bionic bone radial gradient porous NiTi alloy. Background Art

[0002] The aging population and the increasing frequency of traffic accidents are driving an increasing demand for biomedical implants and prostheses. To avoid implant failure caused by "stress shielding" within the implant, porous biomaterials are often used instead of dense biomaterials. Commonly used materials include porous titanium alloys, magnesium alloys, and ceramics. Among these, nickel-titanium alloys are considered the most promising implant material due to their high strength, excellent corrosion resistance, biocompatibility, and shape memory effect.

[0003] Porous materials for bone implants are mostly prepared using powder metallurgy methods, such as press forming and sintering, hot static pressing, and self-propagating high-temperature synthesis. However, these methods make it difficult to obtain complex bone structures, requiring subsequent machining to obtain components of the desired size and shape. Porous materials are generally brittle, and subsequent machining not only destroys the pore structure, thereby affecting the implant effect, but also increases material loss. Furthermore, the prepared porous structures are generally single pore structures, unable to meet the diverse functional requirements of implant materials, thus limiting their application effectiveness and scope. In fact, human bone exhibits a typical radial gradient porosity structure, changing from dense bone to porous bone from the outside to the inside, each meeting the multifunctional requirements of strength support, fluid and nutrient input, and tissue ingrowth. Consequently, the preparation of radial gradient porous materials and components for bone biomimetic structures is gaining increasing attention.

[0004] There are currently three methods for preparing radial gradient porous materials: 3D printing, multi-layer batch pressing and sintering, and centrifugation. The pressing and forming method (CN202110029761.X, CN107790723A, CN102168195A, CN103060589A, CN101818277A, CN106735185A, CN113860906A, and CN108273126B) involves using a mixture containing different powders and pore-forming agents, sometimes combined with mold design, to press and form each layer in sequence, and then sintering. This method involves a complex process, cannot directly produce parts with complex shapes, has distinct interfaces between the layers in the resulting product, and is prone to internal stress and damage when loaded. Furthermore, due to the different mixtures in each layer, the radial shrinkage of each layer during sintering is inconsistent, which can easily lead to product deformation and cracking. 3D printing or additive manufacturing technology (CN09872769, CN106109032A, CN113213910A, CN114732947A, CN113683425A) is mainly to obtain gradient structures through structural design, layer-by-layer printing and sintering. This method undoubtedly has great advantages in the near-net shape of complex products, but there are also some problems that restrict its development, mainly including expensive equipment, high preparation and forming costs, poor product surface accuracy, and unsuitable for mass production. The centrifugal method (CN101418391A, CN102766773A, CN103896624A) mainly utilizes the different densities of various substances in the mixture to achieve gradient changes in the final composition and structure. This method requires special equipment, and the composition and structure control is difficult, so it is not suitable for use in production. In the early stage (CN201611040011.8), we successfully prepared axially gradient porous nickel-titanium alloy by combining gel injection molding and microwave sintering technology. However, we did not solve the problems of radial gradient porous preparation, such as inconsistent shrinkage of radial layers during sintering due to different mixed materials in each layer, which easily led to product deformation and cracking. Summary of the Invention

[0005] The purpose of the present invention is to provide a mold and method for preparing bionic bone radial gradient porous NiTi alloy with near net shape, low cost, high efficiency and no need for special forming equipment.

[0006] In order to achieve the above technical objectives, the present invention provides the following technical solutions:

[0007] The mold for preparing bionic bone radial gradient porous NiTi alloy provided by the present invention includes an outer mold and an inner mold concentrically arranged thereon. The inner mold includes multiple layers of diaphragms arranged inside and outside and a cover plate connected to their upper ends. The planar size of the cover plate is larger than the diameter of the outer mold. Several pouring ports are respectively provided on the cover plate corresponding to the gaps between the diaphragms of the inner membrane and the gap between the outermost diaphragm and the outer mold.

[0008] The inner mold includes 2 to 7 layers of diaphragms.

[0009] The material of the diaphragm is copper foil / aluminum foil; the material of the cover plate is copper / aluminum.

[0010] The method for preparing the bionic bone radial gradient porous NiTi alloy provided by the present invention comprises the following steps:

[0011] Step 1: Slurry preparation

[0012] 1) Preparation of a premix: preparing a monomer and a crosslinking agent at a mass ratio of 10 to 20:1, and dissolving the prepared monomer and crosslinking agent as solutes in an organic solvent to obtain a premix with a monomer mass concentration of 10 to 30 wt%;

[0013] 2) preparing slurries 1#, slurry 2#, ..., and slurry i# in ascending order of the volume concentration of the pore-forming agent in the slurry: preparing nickel powder, titanium powder, and the pore-forming agent according to the designed concentrations and mixing them uniformly to obtain a raw material powder; preparing a dispersant according to 0.5 to 2 wt% of the mass of the prepared nickel-titanium powder; mixing the prepared raw material powder and dispersant with the premixed solution prepared in step 1) to prepare slurries 1#, slurry 2#, ..., and slurry i#;

[0014] In the raw material powder (solid phase) of slurries 1#, slurry 2#, ..., and slurry i#, the volume concentration of the pore-forming agent gradually increases within a range of 0 to 45 vol%, and the difference in the volume concentration of the pore-forming agent in the solid phases of two adjacent slurries is controlled to be ≤10 vol%. The solid phase volume concentrations of slurries 1#, slurry 2#, ..., and slurry i# remain consistent, and the solid phase volume concentration range is 48 to 53 vol%. No pore-forming agent is added to the raw material powder of slurry 1#.

[0015] Step 2: Co-injection molding

[0016] After vacuum degassing slurries 1#, 2#, ..., and i#, 0.4-2 wt% of the monomer weight of the initiator and catalyst are added to each of them and stirred evenly. Then, slurries 1#, 2#, ..., and i# are simultaneously injected from the outermost layer to the innermost layer through the corresponding pouring ports into the corresponding gap layers of the mold. During the pouring, the inner mold is moved in the opposite direction of the slurry injection direction, and the movement speed matches the slurry injection speed to ensure that each layer of slurry is out of contact with the diaphragm at the moment of combination.

[0017] Step 3: Curing and drying

[0018] The co-injection mold base and the outer mold are vacuum cured at 70-80°C to obtain a solidified base after removing the outer mold, and then the temperature is continuously raised to 100-150°C for drying to obtain a dried base;

[0019] Step 4: Degreasing and sintering

[0020] The dried blank is heated to 280-300°C at a heating rate of 2-3°C / min under a protective atmosphere and then kept warm. The temperature is then increased to 500-550°C at a heating rate of 4-6°C / min and kept warm to complete degreasing. The blank is then heated to 980-1100°C at a heating rate of 6-8°C / min and sintered to obtain a sintered sample.

[0021] Step 5: Removal of pore-forming agent

[0022] The sintered sample is desalted in deionized water in a water bath, and then vacuum dried at 100-110° C. to obtain a bionic bone radial gradient porous metal alloy.

[0023] Preferably, the organic solvent is n-octanol, the monomer is hydroxyethyl methacrylate, the crosslinking agent is 1,6-hexanediol diacrylate, the initiator is tert-butyl perbenzoate, the catalyst is N,N-dimethylaniline, and the dispersant is Silok-7456F.

[0024] Preferably, the pore-forming agent is of a place-occupying type, which is required to remain intact even at a high temperature of 1100° C., not chemically react with powders and organic reagents, and be easily dissolved and removed.

[0025] More preferably, the pore-forming agent is NaCl or KCl.

[0026] Preferably, the particle size of the pore-forming agent in the raw material powder (solid phase) of slurry 1#, slurry 2#, ..., slurry i# may also be gradually increased, and the particle size levels may be pre-screened into several levels of 0-75 μm, 75-150 μm, 150-250 μm and >250 μm.

[0027] Preferably, the value of i is any integer from 3 to 8, and is 1 greater than the number of diaphragms in the inner mold of the mold.

[0028] Preferably, in the step 1, the molar ratio of nickel powder to titanium powder is 1:1, the nickel powder particle size is 5 to 45 μm, and the titanium powder particle size is 5 to 45 μm; the nickel powder, titanium powder and pore-forming agent are ball-milled and mixed uniformly, and the mixing conditions are a ball-to-material ratio of (3 to 5): 1, a rotation speed of 100 to 150 rpm, and a ball-milling time of 3 to 5 h; the raw material powder, dispersant and the premixed solution prepared in step 1) are ball-milled and mixed for 10 to 12 h at a ball-to-material ratio of (1 to 2): 1 and a rotation speed of 100 to 150 rpm.

[0029] Preferably, in step three, the outer mold is fixed in an ultrasonic water bath oscillation tank, and the effects of ultrasound and oscillation during the injection molding process are beneficial to the fusion of each layer of slurry and the flow of materials.

[0030] Preferably, in step three, the co-injection mold base and the outer mold are vacuum cured at 70-80° C. for 30-60 minutes to obtain a solidified base after removing the outer mold, and then the temperature is continued to rise to 100-150° C. and dried for 2-8 hours to obtain a dried base.

[0031] Preferably, in the step four, the dried blank is heated to 280-300°C at a heating rate of 2-3°C / min under a high-purity argon protective atmosphere and kept warm for 1-2 hours, then heated to 500-550°C at a heating rate of 4-6°C / min and kept warm for 1-3 hours to complete degreasing, and then heated to 980-1100°C at a heating rate of 6-8°C / min and sintered for 1-2 hours to obtain a sintered sample.

[0032] Preferably, in step five, the sintered sample is desalted in deionized water at 40-60° C. for 10-12 hours, the deionized water is replaced every 1-2 hours, and then vacuum dried at 100-110° C. for 1-2 hours to obtain a bionic bone radial gradient porous metal alloy.

[0033] The radial gradient porous nickel-titanium alloy prepared by the present invention has a relatively continuous porosity change from 15% in the outer layer to a maximum of 70% in the inner layer, an average pore size change from 30 μm in the outer layer to more than 400 μm in the inner layer, and its mechanical properties basically match those of bones.

[0034] The mold and method designed by the present invention can also be used to prepare radial gradient porous materials or products from other powder materials.

[0035] The principles of the present invention are as follows: 1) The total solid volume fraction of each layer of slurry is the same, and the porosity and sintering shrinkage are controlled by changing the pore-forming agent. The pore-forming agent is limited to substances that are infusible at high temperatures but soluble in water. Its main functions are to form pores and to maintain position during sintering, so that the densification and shrinkage rates of each layer of slurry during high-temperature sintering are basically consistent, avoiding or reducing product cracking caused by shrinkage stress during sintering of each layer; 2) The porosity change of each layer of slurry must be controlled within 10%, otherwise it will crack; 3) The effect of the ultrasonic oscillation field is added during co-gelation to facilitate the fusion of each layer of slurry, thereby obtaining a continuous gradient pore change without an interface; 4) To address the problem of inconsistent radial sintering shrinkage and easy cracking, ordinary sintering is also used, and the heating rate is controlled to be low.

[0036] Beneficial effects of the present invention:

[0037] The present invention maintains the same solid phase volume fraction in each layer of slurry (Slurry 1#, Slurry 2#, ..., Slurry i#), then controls the variation of the pore-forming agent content in the solid phase of adjacent slurries to ≤10 vol%. Combined with a low sintering heating rate, this effectively avoids or reduces the phenomenon of inconsistent radial shrinkage stress in each layer during sintering, thereby preventing product deformation or cracking. By controlling the rate of change of the pore-forming agent content in each layer and introducing ultrasonic oscillation, the formation of interfaces between the layers is effectively eliminated, achieving a relatively continuous gradient change in porosity and / or pore size, and avoiding various problems caused by stress concentration caused by load during application. Furthermore, compared to other methods, this method is simple to operate, does not require dedicated forming equipment, is low-cost, and is highly efficient, enabling near-net ... BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the mold designed for preparing radial gradient porous NiTi alloy according to the present invention: (a) outer mold; (b) inner mold; (c) combined mold.

[0039] Figure 2 Schematic diagram of injection molding for preparing radial gradient porous NiTi alloy according to the present invention;

[0040] Figure 3 The process flow chart of preparing radial gradient porous NiTi alloy of the present invention;

[0041] Figure 4 This is a pore distribution diagram from the center to the outer diameter of the radial gradient porous NiTi alloy in Example 1 of the present invention.

[0042] Figure 5 This is the pore distribution diagram from the center to the outer diameter of the radial gradient porous NiTi alloy in Example 2 of the present invention. DETAILED DESCRIPTION

[0043] The mold of the present invention is divided into two parts: inner and outer. The size and shape of the outer mold mainly depend on the shape and size of the implant. It can be a hollow cylinder or a bone-like shape. The material can be plastic, glass and metal, etc. Figure 1 As shown in (a); the inner mold is composed of 2 to 7 layers of very thin copper or aluminum foil diaphragms welded on copper or aluminum plates, similar to the outer mold. Then, pouring gates are opened in the middle of each layer. The number of pouring gates is mainly determined by the volume of each layer, and the pouring gates are generally arranged symmetrically and evenly. See the attached figure. Figure 1 Then press the inner and outer molds Figure 1 (c) Assemble and set aside.

[0044] Example 1

[0045] The inner mold used in this embodiment includes two layers of copper foil diaphragms welded to a copper plate, and the outer mold is a quartz glass cylinder. From the outer to the inner layers, 3, 2, and 1 pouring ports are evenly distributed between the gaps.

[0046] Preparation of slurry 1#: a. Weigh appropriate amounts of 5-8 μm hydrogenated dehydrogenated Ti powder and <45 μm atomized Ni powder in a molar ratio of 1:1, place the two in a planetary ball mill at a ball-to-material ratio of 3:1 and a rotation speed of 120 r / min for 4 hours to obtain a uniformly mixed nickel-titanium mixed powder; b. Add a certain proportion of hydroxyethyl methacrylate monomer and 1,6-hexanediol diacrylate crosslinker to n-octanol solvent to prepare a premix, wherein the mass fraction of the monomer is 30% and the mass ratio of the monomer to the crosslinker is 10:1; c. Add the nickel-titanium mixed powder and 1.5 wt.% of the dispersant Silok-7456F by weight of the nickel-titanium mixed powder to the premix, and place the premix in a planetary ball mill at a rotation speed of 120 r / min for 10 hours to obtain slurry 1# with good fluidity and a solid phase volume fraction of 50 vol.%;

[0047] Preparation of slurries 2# and 3#: NaCl with a diameter of 75 to 150 μm was screened and mixed with uniformly mixed nickel and titanium powders using the same mixing procedure as in step a above. The subsequent steps were the same as steps b and c above to prepare slurry 2# containing 8 vol% NaCl in the solid phase and slurry 3# containing 16 vol% NaCl in the solid phase, respectively. The total solid phase volume fraction of slurry 2# and slurry 3# was 50 vol.%.

[0048] In a vacuum glove box, Figure 1 The outer mold of the assembled mold is placed in an ultrasonic oscillation cleaning machine. 2 wt.% of tert-butyl peroxybenzoate initiator and 1.5 wt.% of N,N-dimethylaniline catalyst are injected into the three slurries respectively. A glass rod is used to stir for 20 seconds. Then, the three slurries are injected into the mold from each pouring port at the same time. Slurry 1# is injected into the outer layer, slurry 2# is injected into the middle layer, and slurry 3# is injected into the inner layer. While injecting, the inner mold is moved upward (see Figure 2As shown), the moving speed of the inner mold matches the injection speed of the slurry so that the layers of slurry contact each other near the lower edge of the diaphragm. The outer mold and the blank are then placed in a drying oven at 70°C for vacuum curing for 45 minutes, and then the outer mold is removed and the temperature is raised to 120°C and dried for 5 hours. The dried blank is then heated to 300°C at a heating rate of 3°C / min and kept warm for 1 hour, then heated to 550°C at 4.5°C / min and kept warm for 1 hour, and then heated to 1050°C at a heating rate of 8°C / min and sintered for 90 minutes. The degreasing and sintering process is carried out under the protection of high-purity argon. Finally, the sintered blank is desalted in a water bath at 45°C deionized water for 12 hours, and the deionized water is replaced every 2 hours. After drying, a bionic bone radial gradient porous NiTi alloy with no obvious interface in the internal layers can be obtained. The porosity of the porous NiTi alloy changes from 55% to 17% from the center to the outer diameter, and the average pore size changes from 35μm to 175μm. Its compressive strength is 130MPa and the compressive elastic modulus is 5.8GPa. The microstructure is shown in the attached figure. Figure 4 .

[0049] Example 2

[0050] The inner mold of the mold used in this embodiment includes four layers of aluminum foil diaphragms welded to an aluminum plate, and the outer mold is a quartz glass cylinder. From the outer to the inner, the gaps between the layers are evenly spaced with 6, 5, 4, 3, and 1 pouring ports, respectively.

[0051] The same method as in Example 1 was adopted to prepare slurry 1#, slurry 2#, slurry 3#, slurry 4# and slurry 5#. The total solid volume fraction of the five slurries was controlled at 50 vol%. No pore-forming agent was added to the solid phase of slurry 1#, slurry 2# contained 10 vol% of NaCl with a particle size of <75 μm in the solid phase, slurry 3# contained 20 vol% of NaCl with a particle size of 75-150 μm in the solid phase, slurry 4# contained 30 vol% of NaCl with a particle size of 150-250 μm in the solid phase, and slurry 5# contained 40 vol% of NaCl with a particle size >250 μm in the solid phase. In the assembled mold, various slurries are injected from each pouring port at the same time. Slurries 1#, 2#, 3#, 4# and inner layer 5# are used in sequence from the outside to the inside. After solidification, drying and degreasing, the obtained green body is heated to 1100°C at a heating rate of 7°C / min and sintered for 90 minutes under high-purity argon protection. Subsequently, after desalination treatment, a bionic bone radial gradient porous NiTi alloy with no obvious interface in each layer is obtained. The porous NiTi alloy has a porosity gradient change from 67% to 15% from the center to the outer diameter, and a gradient change from 32μm to 345μm in average pore size. Its compressive strength is 88MPa, and its compressive elastic modulus is 2.8GPa. Its microstructure is shown in the attached figure. Figure 5 .

[0052] Example 3

[0053] The inner mold used in this example consists of seven layers of diaphragms. These copper foil diaphragms are welded to a copper plate. The outer mold is a cylindrical quartz glass mold. From the outermost layer to the innermost layer, there are 10, 9, 8, 6, 4, 3, 2, and 1 pouring ports evenly spaced between the layers.

[0054] Each slurry was prepared in the same manner as in Example 1: a. An appropriate amount of hydrogenated dehydrogenated Ti powder (<45 μm) and atomized Ni powder (5-10 μm) were weighed in a molar ratio of 1:1, and the two were placed in a planetary ball mill at a ball-to-material ratio of 5:1 and a rotation speed of 150 r / min for 3 h to obtain a uniformly mixed nickel-titanium mixed powder; b. A certain proportion of hydroxyethyl methacrylate monomer and 1,6-hexanediol diacrylate crosslinker were added to n-octanol solvent to prepare a premix, wherein the mass fraction of the monomer was 10% and the mass ratio of the monomer to the crosslinker was 20:1; c. The nickel-titanium mixed powder and 0.5 wt.% of the dispersant Silok-7456F by weight of the nickel-titanium mixed powder were added to the premix, and the mixture was placed in a planetary ball mill at a rotation speed of 100 r / min for 12 h to obtain slurry 1# with a solid phase volume fraction of 53 vol.% and good fluidity. The total solid volume fraction of the eight slurries, slurry 1#, slurry 2#, slurry 3#, slurry 4#, slurry 5#, slurry 6#, slurry 7# and slurry 8#, is controlled at 53 vol%. No pore-forming agent is added to the solid phase of slurry 1#; slurries 2# to 4# use NaCl with a diameter of <75 μm as a pore-forming agent, and its content accounts for 4 vol%, 10 vol% and 16 vol% of the total solid phase, respectively; slurries 5# to 8# use NaCl with a diameter of 75 to 150 μm as a pore-forming agent, and its content accounts for 24 vol%, 32 vol%, 39 vol% and 45 vol% of the total solid phase, respectively. In an assembled mold, various slurries were simultaneously injected through various pouring ports. From the outermost layer to the innermost layer, slurries 1#, 2#, 3#, 4#, 5#, 6#, 7#, and 8# were used sequentially. The resulting green body was vacuum-cured at 80°C for 30 minutes, then heated to 150°C and dried for 2 hours. Under argon protection, the dried green body was heated at a rate of 2°C / min to 280°C and held for 2 hours. The temperature was then increased at a rate of 6°C / min to 500°C and held for 3 hours. Finally, the green body was sintered at a rate of 6°C / min to 980°C for 120 minutes. Finally, the sintered green body was desalted in deionized water at 60°C for 10 hours, with the deionized water replaced every hour. After drying, a bionic bone-inspired radially gradient porous NiTi alloy with no distinct internal interfaces was produced. The porosity of the porous NiTi alloy changes gradually from 72% to 18% from the center to the outer diameter, and the average pore size changes gradually from 37μm to 235μm. Its compressive strength is 108MPa and the compressive elastic modulus is 4.7GPa.

[0055] Example 4

[0056] This example is substantially the same as Example 1, except that the dispersant dosage is 2 wt %, the total solid volume fraction of each slurry is maintained at 48 vol %, the initiator addition amount is 0.4 wt %, the catalyst is 0.4 wt %, the sintering temperature is 980° C., the sintering time is 2 h, and the desalination temperature is 50° C., the time is 11 h. The prepared radially gradient porous NiTi alloy has a porosity gradient from 60% to 20% from the center to the outer diameter, and an average pore size gradient from 42 μm to 195 μm. Its compressive strength is 102 MPa, and its compressive elastic modulus is 4.2 GPa.

[0057] Example 5

[0058] This example is substantially the same as Example 4, except that the dispersant dosage is 1 wt %, the total solid volume fraction of each slurry is maintained at 53 vol %, the initiator addition amount is 1 wt %, the catalyst is 1 wt %, the sintering temperature is 1100° C., and the sintering time is 2 h. The prepared radially gradient porous NiTi alloy exhibits a porosity gradient from 48% to 14% from the center to the outer diameter, and an average pore size gradient from 28 μm to 150 μm. Its compressive strength is 168 MPa, and its compressive elastic modulus is 8.1 GPa.

Claims

1. A method for preparing a bionic bone radial gradient porous NiTi alloy, comprising the following steps: Step 1: Slurry preparation 1) Preparation of premix: Prepare monomer and crosslinker at a mass ratio of 10-20:1, and dissolve the prepared monomer and crosslinker in an organic solvent as solutes to obtain a premix with a monomer mass concentration of 10-30wt%; 2) preparing slurries 1#, slurry 2#, ..., and slurry i# in ascending order of the volume concentration of the pore-forming agent in the slurry: preparing nickel powder, titanium powder, and the pore-forming agent according to the designed concentrations, and mixing them uniformly to obtain raw material powders; preparing a dispersant according to 0.5-2 wt% of the mass of the prepared nickel-titanium powder; and mixing the prepared raw material powders and dispersant with the premixed solution prepared in step 1) to prepare slurries 1#, slurry 2#, ..., and slurry i#; The volume concentration of the pore-forming agent in the raw material powders of slurries 1#, slurry 2#, ..., and slurry i# gradually increases within a range of 0 to 45 vol%, and the difference in the volume concentration of the pore-forming agent in the solid phases of two adjacent slurries is controlled to be ≤10 vol%. The solid phase volume concentration of slurries 1#, slurry 2#, ..., and slurry i# remains consistent, and the solid phase volume concentration ranges from 48 to 53 vol%. Step 2: Co-injection molding The mold used includes an outer mold and an inner mold concentrically arranged therewith. The inner mold includes multiple layers of diaphragms arranged inside and outside and a cover plate connected to their upper ends. The planar size of the cover plate is larger than the diameter of the outer mold. A plurality of pouring ports are respectively provided on the cover plate corresponding to the gaps between the layers of the inner membrane and the gap between the outermost diaphragm and the outer mold. The material of the diaphragm is copper foil / aluminum foil; the material of the cover plate is copper / aluminum; the inner mold includes 2 to 7 layers of diaphragms; After vacuum degassing slurry 1#, slurry 2#, ..., and slurry i#, 0.4-2 wt% of the monomer weight of the initiator and catalyst are added respectively and stirred evenly. Then, from the outer layer to the inner layer, slurry 1#, slurry 2#, ..., and slurry i# are injected into the corresponding gap layer from the corresponding pouring port at the same time. During the pouring, the inner mold moves in the opposite direction of the slurry injection direction, and the movement speed matches the slurry injection speed to ensure that each layer of slurry is out of contact with the diaphragm at the moment of combination. Step 3: Curing and drying The co-injection mold base and the outer mold are vacuum cured at 70-80°C to obtain a solidified base after removing the outer mold, and then the temperature is continuously raised to 100-150°C for drying to obtain a dried base; Step 4: Degreasing and sintering The dried blank was heated to 280-300°C at a heating rate of 2-3°C / min and kept warm under a protective atmosphere. The temperature was then increased to 500-550°C at a heating rate of 4-6°C / min and kept warm to complete debinding. The blank was then heated to 980-1100°C at a heating rate of 6-8°C / min and sintered to obtain a sintered sample. Step 5: Removal of pore-forming agent The sintered sample was desalted in deionized water and then vacuum dried at 100-110°C to obtain a bionic bone radial gradient porous metal alloy. In the step 4, the dried blank is heated to 280-300°C at a heating rate of 2-3°C / min under a high-purity argon protective atmosphere and kept warm for 1-2 hours, then heated to 500-550°C at a heating rate of 4-6°C / min and kept warm for 1-3 hours to complete degreasing, and then heated to 980-1100°C at a heating rate of 6-8°C / min and sintered for 1-2 hours to obtain a sintered sample.

2. The method according to claim 1, wherein: The organic solvent is n-octanol, the monomer is hydroxyethyl methacrylate, the crosslinking agent is 1,6-hexanediol diacrylate, the initiator is tert-butyl peroxybenzoate, the catalyst is N,N-dimethylaniline, and the dispersant is Silok-7456F.

3. The method according to claim 1, wherein: The pore-forming agent is of a place-occupying type and is required to remain intact even at a high temperature of 1100° C., not to chemically react with powders and organic reagents, and to be easily dissolved and removed.

4. The method according to claim 3, wherein: The pore-forming agent is NaCl or KCl.

5. The method according to claim 1, wherein: The value of i is any integer between 3 and 8.

6. The method according to claim 1, wherein: In the step 5, the sintered sample is desalted in deionized water at 40-60° C. for 10-12 hours, the deionized water is replaced every 1-2 hours, and then vacuum dried at 100-110° C. for 1-2 hours to obtain a bionic bone radial gradient porous metal alloy.

Images