Method for manufacturing medical titanium alloy with dense surface and porous interior

Abstract

The present application relates to a kind of medical titanium alloy preparation method of surface layer dense internal porous, belong to the field of biomedical materials.It is characterized in that comprising the following steps:1) spherical Ti6Al4V5Cu powder is used as raw material;2) raw material is mixed with liquid paraffin and obtains mixture I;3) raw material is mixed with NH4HCO3 pore-forming agent and obtains mixture II;4) mixture I is filled into stainless steel mold and is pressed into hollow cylinder, then mixture II is filled and is pressed into shape;5) it is placed in tubular furnace and is carried out heat defatting;6) after defatting, blank is placed in graphite mold, is placed in spark plasma sintering furnace and is sintered to obtain surface layer dense internal porous Ti6Al4V5Cu medical titanium alloy.The medical titanium alloy prepared by the method of the present application has high compressive strength (≥872MPa) and low elastic modulus (≤16GPa), and has interconnected porous structure in the interior, not only can promote the growth of bone tissue, but also can play the role of stress release and buffer movement load, and has certain antibacterial property.

Description

Technical Field

[0001] The invention relates to a method for preparing a medical titanium alloy with a dense surface and porous interior, and belongs to the field of biomedical materials. Background Art

[0002] An intervertebral implant is a medical implant used during spinal fusion surgery, primarily for the treatment of spinal conditions such as herniated disc, spondylolisthesis, spinal instability, scoliosis, spinal tumors, spinal infection, or spinal fractures. Its primary function is to fill the intervertebral space after the damaged disc or vertebral body is removed, providing support and stability and promoting bone fusion between adjacent vertebrae. Currently, the most commonly used Ti6Al4V alloy titanium cage for intervertebral implants, while biocompatible and stable, has a certain degree of stability. However, due to the mismatch between the elastic modulus of Ti6Al4V alloy and human bone, problems such as implant sinking and stress shielding within adjacent vertebrae can easily occur after surgery. Furthermore, Ti6Al4V alloy lacks antibacterial properties and can easily lead to bacterial infection after surgery. This not only shortens the lifespan of the implant but can also cause implant failure, causing significant pain and financial burden to patients. A large number of studies have shown that by adding copper to Ti6Al4V alloy, not only the strength and corrosion resistance of the alloy are improved, but also it is endowed with unique antibacterial capabilities. In particular, Ti6Al4V5Cu alloy not only has good mechanical properties, but also has a killing rate of up to 98% against Staphylococcus aureus. Summary of the Invention

[0003] In order to overcome the shortcomings of the existing technology, especially the problems of elastic modulus mismatch and lack of antibacterial properties of intervertebral implant materials made of existing titanium alloys, the present invention provides a method for preparing a medical titanium alloy with a dense surface and a porous interior.

[0004] The present invention is accomplished by the following technical solution: a method for preparing a medical titanium alloy with a dense surface and a porous interior, characterized by comprising the following steps:

[0005] (1) Spherical Ti6Al4V5Cu titanium alloy powder with a particle size of 10 to 20 μm is used as raw material;

[0006] (2) adding the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) to liquid paraffin as a binder at an amount of 6.13-6.54 g / ml, heating to 20-30° C., stirring and mixing uniformly to obtain mixture I, which is set aside;

[0007] (3) adding NH4HCO3 powder having a particle size of 300 to 500 μm and serving as a pore-forming agent to the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) at a mass ratio of 35 to 45%, and mixing them uniformly to obtain a mixture II for standby use;

[0008] (4) Filling the mixture I of step (2) into a stainless steel mold and pressing it into a hollow cylinder, then filling the hollow cylinder with the mixture II of step (3), cold pressing, and removing the mold to obtain a green body with the outer layer of the mixture I and the inner layer of the mixture II;

[0009] (5) placing the green body of step (4) into a tubular furnace, heating the body to 200-300°C at a rate of 4-8°C / min under a vacuum of 10-25 Pa and a continuous flow of 99.99% pure argon atmosphere, and keeping the temperature for 240-300 min to complete thermal degreasing, followed by cooling to room temperature in the furnace for later use;

[0010] (6) The green body after thermal degreasing in step (5) is placed in a graphite mold, placed in a spark plasma sintering furnace, evacuated to 4-6 Pa, heated to 550-650°C at a heating rate of 80-90°C / min, then heated to 850-900°C at a heating rate of 90-110°C / min, and finally heated to 1100-1200°C at a heating rate of 40-50°C / min, kept warm for 8-12 minutes to complete spark plasma sintering, and then cooled to room temperature with the furnace to obtain a Ti6Al4V5Cu medical titanium alloy with a dense surface and porous interior.

[0011] Preferably, the chemical composition of the spherical Ti6Al4V5Cu titanium alloy powder in step (1) is as follows: Al: 5.50-6.50wt.%, V: 3.50-4.50wt.%, Cu: 4.50-6.0wt.%, Fe: ≤0.25wt.%, C: ≤0.08wt.%, N: ≤0.03wt.%, H: ≤0.008wt.%, O: ≤0.13wt.%, and the balance is Ti.

[0012] Preferably, the spherical Ti6Al4V5Cu titanium alloy powder in step (1) is prepared by electrode induction melting and inert gas atomization method.

[0013] Preferably, the pressing process of step (4) is unidirectional pressing, the pressing rate is 1 to 3 kN / min, the pressure is 45 to 50 kN, and the holding time is 25 to 30 min.

[0014] The stainless steel mold of step (4) includes: a sleeve with a base at the bottom and a vertical cavity therein, a pad is provided at the bottom of the vertical cavity, and also includes a fixed cylinder that can be placed in the vertical cavity of the sleeve, a core rod placed in the fixed cylinder, and a mold pressure rod that can be placed in the vertical cavity of the sleeve.

[0015] The graphite mold structure of step (6) is: a cylindrical shell with a cylindrical inner cavity, and plugs are respectively connected to both ends of the cylindrical shell.

[0016] The present invention has the following advantages and beneficial effects:

[0017] The present invention uses the above-mentioned technical solution to prepare a Ti6Al4V5Cu medical titanium alloy with a dense surface and porous interior. While achieving high strength, low elastic modulus and antibacterial properties, it also has an interconnected internal porous structure that can promote the ingrowth of bone tissue. The spherical Ti6Al4V5Cu titanium alloy powder prepared by the electrode induction melting inert gas atomization method is used as the raw material. It has the advantages of high sphericity, good fluidity, high purity and low gas impurity content. The pre-alloyed spherical Ti6Al4V5Cu titanium alloy powder is sintered using spark plasma sintering technology to achieve precise control of elements and effectively avoid the segregation problem of the chemical composition of the sintered product. In addition, the use of pre-alloyed spherical Ti6Al4V5Cu titanium alloy powder significantly reduces the activation energy of metal atom diffusion, thereby reducing the sintering temperature and energy consumption, which helps to reduce costs. The prepared surface dense / interior porous medical titanium alloy has high compressive strength (≥872MPa) and low elastic modulus (≤16GPa), and the interior of the surface dense and interior porous medical titanium alloy presents an interconnected porous structure (porosity of 50% to 68%), which not only promotes the growth of bone tissue, but also plays a role in stress release and buffering motion load when the material is deformed by stress. At the same time, copper ions (Cu + ) and body fluids can be transmitted between the internal porous structure and bone tissue, giving the alloy a certain antibacterial property. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a morphology image of the spherical Ti6Al4V5Cu titanium alloy powder used in the present invention;

[0019] Figure 2 This is a structural diagram of a stainless steel mold used in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the pre-pressing process after powder filling according to the present invention;

[0021] Figure 4 This is the interface morphology of the Ti6Al4V5Cu medical titanium alloy cylinder with dense surface and porous interior prepared in Example 2 of the present invention;

[0022] Figure 5 This is a compressive strength-elastic modulus graph of the Ti6Al4V5Cu medical titanium alloy cylinder with dense surface and porous interior prepared in Examples 1, 2, and 3 of the present invention;

[0023] Figure 6 This is a compressive strength-elastic modulus diagram of the Ti6Al4V5Cu medical titanium alloy cylinder with dense surface and porous interior prepared in Examples 2, 4, and 5 of the present invention.

[0024] Figure 2 Middle: 1-core rod; 2-fixing cylinder; 3-sleeve; 4-base at the lower end; 5-mold pressure rod, 6-pad at the bottom of the vertical cavity of the sleeve; DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited to the above contents.

[0026] Example 1

[0027] A method for preparing a medical titanium alloy with a dense surface and a porous interior, characterized by comprising the following steps:

[0028] (1) Spherical Ti6Al4V5Cu titanium alloy powder prepared by electrode induction melting and inert gas atomization method was used as raw material, and its particle size was 10 μm;

[0029] The chemical composition of the spherical Ti6Al4V5Cu titanium alloy powder is as follows: Al: 6.08 wt.%, V: 3.98 wt.%, Cu: 5.01 wt.%, Fe: 0.028 wt.%, C: 0.011 wt.%, N: 0.007 wt.%, H: 0.0015 wt.%, O: 0.067 wt.%, and the balance is Ti;

[0030] (2) adding 6.13 g / ml of the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) to liquid paraffin as a binder, heating the mixture to 20° C., and stirring the mixture to obtain a mixture I for later use;

[0031] (3) The spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) was added with NH4HCO3 powder having a particle size of 300 μm and used as a pore-forming agent at a mass ratio of 40%, and the mixture was mixed evenly to obtain a mixture II for standby use; the purity of the NH4HCO3 powder used as a pore-forming agent was analytically pure and had a particle size of 300 μm;

[0032] (4) The stainless steel mold used in this step includes: a base 4 at the bottom, a sleeve 3 with a vertical cavity therein, a pad 6 at the bottom of the vertical cavity, a fixed cylinder 2 that can be placed in the vertical cavity of the sleeve 3, a core rod 1 placed in the fixed cylinder 2, and a mold pressure rod 5 that can be placed in the vertical cavity of the sleeve 3; during operation: the pad 6 is placed in the vertical cavity of the sleeve 3, the core rod 1 is inserted into the vertical cavity of the sleeve 3, and then the mixture I of step (2) is filled into the vertical cavity of the sleeve 3, the fixed cylinder 2 is inserted, and the mixture inside is manually pressed. Ⅰ is pressed into a hollow cylinder, then the core rod 1 is pulled out, and the mixture II in step (3) is filled into the vertical cavity of the fixed tube 2, and the core rod 1 is inserted again. The core rod 1 is manually pressed to compact the mixture II in the hollow cylinder, and the core rod 1 and the fixed tube 2 are pulled out, and the mold pressure rod 5 is inserted, and then sent to a conventional press, and unidirectional pressure is applied to 45 kN at a pressure rate of 1 kN / min, and the pressure is maintained for 30 minutes to complete the cold pressing molding, and then demolding is performed to obtain a cylindrical green body with an outer layer of dense mixture I and an inner core of porous mixture II;

[0033] (5) The cylindrical green body obtained in step (4) was placed in a tubular furnace, and heated to 250°C at a rate of 5°C / min under a vacuum of 10 Pa and a continuous flow of 99.99% pure argon atmosphere. The temperature was kept at this temperature for 280 min to complete thermal degreasing, and then the green body was cooled to room temperature in the furnace for use.

[0034] (6) The cylinder that has been thermally degreased in step (5) is placed in a graphite mold, and then placed in a spark plasma sintering furnace. After evacuating to 5 Pa, the temperature is increased to 590°C at a heating rate of 85°C / min, then increased to 880°C at a heating rate of 100°C / min, and finally increased to 1200°C at a heating rate of 45°C / min. The temperature is kept at this temperature for 10 minutes to complete the spark plasma sintering, and then cooled to room temperature with the furnace to obtain a Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior;

[0035] The graphite mold structure is: a cylindrical shell with a cylindrical inner cavity, and plugs are respectively connected to both ends of the cylindrical shell.

[0036] The dimensions of the cold-pressed green body and the sintered sample were measured using a vernier caliper, and the shrinkage of the sample was calculated using a conventional calculation formula. The radial and axial shrinkage rates of the Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior were 12.10% and 10.87%, respectively.

[0037] The dense layer and the porous layer were cut into 3mm×3mm×3mm samples respectively using the electric spark wire cutting method, and polished with 400-grit sandpaper to expose the surface with metallic luster. The density of the dense layer and the porosity of the porous layer were measured according to the Archimedes drainage method. The density of the surface dense layer of the Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior was 93.1%, and the porosity of the internal porous layer was 58.5%.

[0038] The mechanical properties of the material were tested for compression properties according to GB / T 31930-2015. In order to make the test statistically significant, the average value was obtained after multiple tests. The test results are shown in Figure 5 The Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and porous interior has high compressive strength and a low elastic modulus. The compressive strength is 1104MPa, the yield strength is 775.9MPa, and the elastic modulus is 15.1GPa, which matches the elastic modulus of human bones (2-30GPa). After implantation, it has both load-bearing capacity and can disperse stress, reduce stress shielding, and is conducive to long-term and effective implantation.

[0039] Example 2

[0040] A method for preparing a medical titanium alloy with a dense surface and a porous interior, characterized by comprising the following steps:

[0041] (1) Spherical Ti6Al4V5Cu titanium alloy powder prepared by electrode induction melting and inert gas atomization method was used as raw material, and its particle size was 10 μm;

[0042] The chemical composition of the spherical Ti6Al4V5Cu titanium alloy powder is as follows: Al: 6.08 wt.%, V: 3.98 wt.%, Cu: 5.01 wt.%, Fe: 0.028 wt.%, C: 0.011 wt.%, N: 0.007 wt.%, H: 0.0015 wt.%, O: 0.067 wt.%, and the balance is Ti;

[0043] (2) adding 6.13 g / ml of the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) to liquid paraffin as a binder, heating the mixture to 20° C., and stirring the mixture to obtain a mixture I for later use;

[0044] (3) Add 40% by mass of NH4HCO3 powder with a particle size of 300 μm as a pore-forming agent to the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1), mix them evenly, and obtain mixture II for standby use; the purity of the NH4HCO3 powder used as the pore-forming agent is analytical grade;

[0045] (4) The stainless steel mold used in this step is the same as that in Example 1; the pad 6 is placed in the vertical cavity of the sleeve 3, the core rod 1 is inserted into the vertical cavity of the sleeve 3, and then the mixture I of step (2) is filled into the vertical cavity of the sleeve 3, the fixed cylinder 2 is inserted, and the mixture I inside is pressed manually to be pressed into an internal hollow cylinder, then the core rod 1 is pulled out, and the mixture II of step (3) is filled into the vertical cavity of the fixed cylinder 2, and the core rod 1 is inserted again, and the core rod 1 is pressed manually to compact the mixture II in the hollow cylinder, the core rod 1 and the fixed cylinder 2 are pulled out, and the mold pressure rod 5 is inserted, and then sent to a conventional press, and unidirectionally pressurized to 50 kN at a pressurization rate of 2 kN / min, and the pressure is maintained for 25 minutes to complete the cold pressing molding, and then demolded to obtain a cylindrical green body with a dense outer layer of the mixture I and a porous inner core of the mixture II;

[0046] (5) The cylindrical green body of step (4) was placed in a tubular furnace, and heated to 200°C at a rate of 4°C / min under a vacuum of 15 Pa and a continuous flow of 99.99% pure argon atmosphere. The temperature was kept at this temperature for 260 min to complete thermal degreasing, and then cooled to room temperature in the furnace for use;

[0047] (6) The cylinder that has been thermally degreased in step (5) is placed in a graphite mold, and then placed in a spark plasma sintering furnace. After evacuating to 5 Pa, the temperature is increased to 650°C at a heating rate of 90°C / min, then increased to 850°C at a heating rate of 90°C / min, and finally increased to 1150°C at a heating rate of 50°C / min. The temperature is kept at this temperature for 12 minutes to complete the spark plasma sintering, and then cooled to room temperature with the furnace to obtain a Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior; the graphite mold structure is the same as that in Example 1.

[0048] The dimensions of the cold-pressed green body and sintered sample were measured with a vernier caliper, and the shrinkage of the sample was calculated using a conventional formula. The radial and axial shrinkage rates of the Ti6Al4V5Cu medical titanium alloy cylinder, which has a dense surface and a porous interior, were 11.9% and 10.48%, respectively.

[0049] The dense layer and the porous layer were cut into 3mm×3mm×3mm samples respectively using the electric spark wire cutting method, and polished with 400-grit sandpaper to reveal the surface with metallic luster. The density of the dense layer and the porosity of the porous layer were measured according to the Archimedes drainage method. The density of the surface dense layer of the Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior was 92.5%, and the porosity of the internal porous layer was 61.0%.

[0050] The Ti6Al4V5Cu medical titanium alloy cylinder with dense surface and porous interior obtained in Example 2 was observed by metallographic microscope. Figure 3As shown, the interface between the dense and porous layers is well-developed, with uniform structure and no cracks. The porous layer, due to the volatilization of the pore-forming agent NH₄HCO₃, forms evenly distributed pores of varying sizes, with pore sizes primarily ranging from 200 to 700 μm, meeting the requirements for bone cell growth.

[0051] The mechanical properties of the material were tested for compression properties according to GB / T 31930-2015. In order to make the test statistically significant, the average value was obtained after multiple tests. The test results are shown in Figure 5 The Ti6Al4V5Cu medical titanium alloy with a dense surface and porous interior has high compressive strength and low elastic modulus. The compressive strength is 1040.2 MPa, the yield strength is 762.9 MPa, and the elastic modulus is 14.6 GPa, which has an elastic modulus matching that of human bones (2-30 GPa). After implantation, it has both load-bearing capacity and can disperse stress, reduce stress shielding, and is conducive to long-term and effective implantation.

[0052] Example 3

[0053] A method for preparing a medical titanium alloy with a dense surface and a porous interior, characterized by comprising the following steps:

[0054] (1) Spherical Ti6Al4V5Cu titanium alloy powder prepared by electrode induction melting and inert gas atomization method was used as raw material, and its particle size was 15 μm;

[0055] The chemical composition of the spherical Ti6Al4V5Cu titanium alloy powder is as follows: Al: 6.08 wt.%, V: 3.98 wt.%, Cu: 5.01 wt.%, Fe: 0.028 wt.%, C: 0.011 wt.%, N: 0.007 wt.%, H: 0.0015 wt.%, O: 0.067 wt.%, and the balance is Ti;

[0056] (2) adding 6.34 g / ml of the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) to liquid paraffin as a binder, heating the mixture to 25° C., and stirring the mixture to obtain a mixture I for later use;

[0057] (3) Add 400 μm NH4HCO3 powder as a pore-forming agent to the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) at a mass ratio of 40%, mix well, and obtain mixture II for standby use; the purity of the NH4HCO3 powder used as a pore-forming agent is analytical grade and the particle size is 400 μm;

[0058] (4) The stainless steel mold used in this step is the same as that in Example 1; the cushion block 6 is placed in the vertical cavity of the sleeve 3, the core rod 1 is inserted into the vertical cavity of the sleeve 3, and then the mixture I of step (2) is filled into the vertical cavity of the sleeve 3, the fixed cylinder 2 is inserted, and the mixture I therein is manually pressed to be pressed into an internal hollow cylinder, then the core rod 1 is pulled out, and the mixture II of step (3) is filled into the vertical cavity of the fixed cylinder 2, and the core rod 1 is inserted again, and the core rod 1 is manually pressed to compact the mixture II in the hollow cylinder, the core rod 1 and the fixed cylinder 2 are pulled out, and the mold pressure rod 5 is inserted, and then sent to a conventional press, and unidirectionally pressurized to 48 kN at a pressurization rate of 3 kN / min, and the pressure is maintained for 28 minutes to complete the cold pressing molding, and then demolded to obtain a cylindrical green body with an outer layer of dense mixture I and an inner core of porous mixture II;

[0059] (5) The cylindrical green body from step (4) was placed in a tubular furnace, heated to 270°C at a rate of 7°C / min under a vacuum of 20 Pa and a continuous flow of 99.99% pure argon atmosphere, and kept at this temperature for 300 min to complete thermal debinding. The green body was then cooled to room temperature in the furnace and set aside for use.

[0060] (6) The cylinder that has been thermally degreased in step (5) is placed in a graphite mold, and then placed in a spark plasma sintering furnace. After evacuating to 4 Pa, the temperature is increased to 550°C at a heating rate of 80°C / min, then increased to 900°C at a heating rate of 110°C / min, and finally increased to 1100°C at a heating rate of 50°C / min. The temperature is kept at this temperature for 9 minutes to complete the spark plasma sintering, and then cooled to room temperature with the furnace to obtain a Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior; the graphite mold structure is the same as that in Example 1.

[0061] The dimensions of the cold-pressed green body and sintered sample were measured with a vernier caliper, and the shrinkage of the sample was calculated using a conventional formula. The radial and axial shrinkage rates of the Ti6Al4V5Cu medical titanium alloy cylinder, which has a dense surface and a porous interior, were 10.20% and 9.53%, respectively.

[0062] Using wire-cut electrospark cutting, the dense layer and porous layer were cut into 3mm x 3mm x 3mm specimens, then polished with 400-grit sandpaper to reveal a metallic surface. The density of the dense layer and the porosity of the porous layer were measured using the Archimedean drainage method. The density of the dense layer and the porosity of the porous layer of the Ti6Al4V5Cu medical titanium alloy cylinder, which has a dense surface and a porous interior, was 91.3%, while the porosity of the porous layer was 61.7%.

[0063] Table 1 shows the effect of sintering temperature on the density of the dense layer and the porosity of the porous layer of medical titanium alloy with dense surface and porous interior in Examples 1, 2 and 3;

[0064] Table 1

[0065]

[0066]

[0067] As can be seen from Table 1, the surface dense layer of the surface dense and internal porous medical titanium alloy material has a density greater than 90%, and the internal porous layer has a porosity of about 60%, which belongs to the high porosity category. Most of these pores form a network structure, which not only facilitates the ingrowth of bone cells and the formation of capillaries, but also plays a stress release role in the overall stress deformation of the material, so that the material can absorb more energy when deformed.

[0068] The mechanical properties of the material were tested for compression performance according to GB / T 31930-2015. In order to test statistically, multiple tests were taken for average, and the test results are shown in Table 1. Figure 5 The surface dense and internal porous Ti6Al4V5Cu medical titanium alloy material has high compressive strength and low elastic modulus. The compressive strength is 872 MPa, the yield strength is 636.4 MPa, and the elastic modulus is 13.8 GPa. It has a matching elastic modulus with human bone (2-30 GPa). After implantation, the Ti6Al4V5Cu medical titanium alloy material not only has load-bearing capacity but also can disperse stress, reduce stress shielding, and is conducive to long-term effective implantation.

[0069] Example 4

[0070] A method for preparing a surface dense and internal porous medical titanium alloy, characterized in that it comprises the following steps:

[0071] (1) Using spherical Ti6Al4V5Cu titanium alloy powder prepared by electrode induction melting and inert gas atomization method as raw material, the particle size is 20 μm;

[0072] The chemical composition of the spherical Ti6Al4V5Cu titanium alloy powder is as follows: Al: 6.08 wt.%, V: 3.98 wt.%, Cu: 5.01 wt.%, Fe: 0.028 wt.%, C: 0.011 wt.%, N: 0.007 wt.%, H: 0.0015 wt.%, O: 0.067 wt.%, and the balance is Ti;

[0073] (2) The spherical Ti6Al4V5Cu titanium alloy powder of step (1) is added to liquid paraffin as a binder at a quantity of 6.54 g / ml, heated to 30°C, and stirred and mixed uniformly to obtain mixture I, which is ready for use;

[0074] (3) The spherical Ti6Al4V5Cu titanium alloy powder of step (1) is mixed with 35% by mass of NH4HCO3 powder with a particle size of 500 μm as a pore-forming agent to obtain a mixture II, which is ready for use. The purity of the NH4HCO3 powder used as a pore-forming agent is analytical pure, and the particle size is 500 μm;

[0075] (4) The stainless steel mold used in this step is the same as in Example 1. The cushion block 6 is placed in the vertical cavity of the sleeve 3, the core rod 1 is inserted into the vertical cavity of the sleeve 3, and then the mixture I of step (2) is filled into the vertical cavity of the sleeve 3. The fixed cylinder 2 is inserted, and the mixture I in the fixed cylinder 2 is pressed into a hollow cylinder by hand. Then the core rod 1 is pulled out, the mixture II of step (3) is filled into the vertical cavity of the fixed cylinder 2, and the core rod 1 is inserted again. The mixture II is pressed into the hollow cylinder by hand pressing the core rod 1. The core rod 1 and the fixed cylinder 2 are pulled out, and then the mold pressing rod 5 is inserted. The mold is sent to a conventional pressing machine, and unidirectional pressing is performed at a pressing rate of 2 kN / min to 48 kN. The pressure is maintained for 27 min, and the cold pressing is completed. Then the mold is demolded to obtain a green body of a cylinder with a dense mixture I on the outer layer and a porous mixture II in the inner core.

[0076] (5) The cylinder green body of step (4) is placed in a tube furnace. The vacuum degree is 25 Pa, and the purity of the argon atmosphere is 99.99%. The temperature is raised to 250℃ at a rate of 5℃ / min, and the temperature is maintained for 270 min. The thermal debinding is completed, and then the furnace is cooled to room temperature for use.

[0077] (6) The cylinder that has completed thermal debinding in step (5) is placed in a graphite mold, and then placed in a spark plasma sintering furnace. The vacuum degree is 5 Pa, and the temperature is raised to 580℃ at a rate of 85℃ / min, then to 880℃ at a rate of 96℃ / min, and finally to 1150℃ at a rate of 47℃ / min. The temperature is maintained for 10 min, and the spark plasma sintering is completed. Then the furnace is cooled to room temperature to obtain a Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior.

[0078] The dense layer and the porous layer are cut into 3mm×3mm×3mm samples by electric spark wire cutting. The samples are polished using 400 mesh sandpaper to expose the metal luster surface. The density of the dense layer and the porosity of the porous layer are measured by the Archimedes drainage method. The density of the dense surface layer of the Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior is 92.3%, and the porosity of the porous interior layer is 53.2%.

[0079] The mechanical properties of the material were tested for compression properties according to GB / T 31930-2015. In order to make the test statistically significant, the average value was obtained after multiple tests. The test results are shown in Figure 6 The Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and porous interior has high compressive strength and a low elastic modulus. The compressive strength is 1079.1 MPa, the yield strength is 769.1 MPa, and the elastic modulus is 14.8 GPa, which matches the elastic modulus of human bones (2-30 GPa). After implantation, the Ti6Al4V5Cu medical titanium alloy material has both load-bearing capacity and can disperse stress, reducing stress shielding, which is conducive to long-term and effective implantation.

[0080] Example 5

[0081] A method for preparing a medical titanium alloy with a dense surface and a porous interior, characterized by comprising the following steps:

[0082] (1) Spherical Ti6Al4V5Cu titanium alloy powder prepared by electrode induction melting and inert gas atomization method was used as raw material, and its particle size was 20 μm;

[0083] The chemical composition of the spherical Ti6Al4V5Cu titanium alloy powder is as follows: Al: 6.08 wt.%, V: 3.98 wt.%, Cu: 5.01 wt.%, Fe: 0.028 wt.%, C: 0.011 wt.%, N: 0.007 wt.%, H: 0.0015 wt.%, O: 0.067 wt.%, and the balance is Ti;

[0084] (2) adding 6.54 g / ml of the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) to liquid paraffin as a binder, heating the mixture to 30° C., and stirring the mixture to obtain a mixture I for later use;

[0085] (3) Add 500 μm NH4HCO3 powder as a pore-forming agent to the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) at a mass ratio of 45%, mix well, and obtain mixture II for standby use; the purity of the NH4HCO3 powder used as a pore-forming agent is analytical grade and the particle size is 500 μm;

[0086] (4) The stainless steel mold used in this step is the same as that in Example 1; the cushion block 6 is placed in the vertical cavity of the sleeve 3, the core rod 1 is inserted into the vertical cavity of the sleeve 3, and then the mixture I of step (2) is filled into the vertical cavity of the sleeve 3, the fixed cylinder 2 is inserted, and the mixture I inside is pressed manually to be pressed into an internal hollow cylinder, then the core rod 1 is pulled out, and the mixture II of step (3) is filled into the vertical cavity of the fixed cylinder 2, and the core rod 1 is inserted again, and the core rod 1 is pressed manually to compact the mixture II in the hollow cylinder, the core rod 1 and the fixed cylinder 2 are pulled out, and the mold pressure rod 5 is inserted, and then sent to a conventional press, unidirectionally pressurized to 46 kN at a pressurization rate of 1 kN / min, and the pressure is maintained for 29 minutes to complete the cold pressing molding, and then demolded to obtain a cylindrical green body with an outer layer of dense mixture I and an inner core of porous mixture II;

[0087] (5) The cylindrical green body obtained in step (4) was placed in a tubular furnace, and heated to 270°C at a rate of 7°C / min under a vacuum of 20 Pa and a continuous flow of 99.99% pure argon atmosphere. The temperature was kept at this temperature for 260 min to complete thermal degreasing, and then the green body was cooled to room temperature in the furnace for later use.

[0088] (6) The cylinder that has been thermally degreased in step (5) is placed in a graphite mold, and then placed in a spark plasma sintering furnace. After evacuating to 6 Pa, the temperature is increased to 560°C at a heating rate of 82°C / min, then increased to 890°C at a heating rate of 110°C / min, and finally increased to 1150°C at a heating rate of 48°C / min. The temperature is kept at this temperature for 10 minutes to complete the spark plasma sintering, and then cooled to room temperature in the furnace to obtain a Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior. The graphite mold structure is the same as that in Example 1.

[0089] The dense layer and the porous layer were cut into 3mm×3mm×3mm samples respectively using the electric spark wire cutting method, and polished with 400-grit sandpaper to reveal the surface with metallic luster. The density of the dense layer and the porosity of the porous layer were measured according to the Archimedes drainage method. The density of the surface dense layer of the Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and a porous interior was 92.6%, and the porosity of the internal porous layer was 65.3%.

[0090] Table 2 shows the effect of the mass fraction of ammonium bicarbonate on the porosity of the porous layer of medical titanium alloy with dense surface and porous interior in Examples 2, 4, and 5;

[0091] Table 2

[0092] Mass fraction of ammonium bicarbonate (wt%) 35 40 45 Porosity (%) 53.2％ 61.0％ 65.3％

[0093] The mechanical properties of the material were tested for compression properties according to GB / T 31930-2015. In order to make the test statistically significant, the average value was obtained after multiple tests. The test results are shown in Figure 6 As can be seen, as the content of the internal pore-forming agent increases, the compressive strength and elastic modulus of the Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and porous interior show a downward trend. When the mass fraction of the pore-forming agent content is 45%, the Ti6Al4V5Cu medical titanium alloy cylinder with a dense surface and porous interior has high compressive strength while also having a low elastic modulus, with a compressive strength of 984.1 MPa, a yield strength of 744.6 MPa, and an elastic modulus of 14.1 GPa, which matches the elastic modulus of human bone (2-30 GPa). After implantation, the Ti6Al4V5Cu medical titanium alloy material has both load-bearing capacity and can disperse stress, reducing stress shielding and facilitating long-term and effective implantation.

[0094] In summary, the medical titanium alloy with a dense surface and porous interior prepared by the present invention has high compressive strength (≥872MPa) and low elastic modulus (≤16GPa), and the interior of the medical titanium alloy with a dense surface and porous interior presents a porous structure interconnected with each other (porosity of 50% to 68%), which not only promotes the ingrowth of bone tissue, but also plays a role in stress release and buffering motion loads when the material as a whole is subjected to stress and deformation; at the same time, copper ions and body fluids can be transmitted between the internal porous structure and bone tissue, giving the alloy a certain antibacterial property.

[0095] The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any modification and replacement based on the technical solution and inventive concept provided by the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a medical titanium alloy with a dense surface and porous interior, characterized in that The following steps are included: (1) Spherical Ti6Al4V5Cu titanium alloy powder with a particle size of 10~20μm is used as raw material; (2) Add the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) to liquid paraffin as a binder at an amount of 6.13-6.54 g / ml, heat to 20-30°C, and stir to mix uniformly to obtain mixture I, which is set aside; (3) Add NH4HCO3 powder with a particle size of 300-500 μm and used as a pore-forming agent to the spherical Ti6Al4V5Cu titanium alloy powder prepared in step (1) at a mass ratio of 35-45%, mix well, and obtain mixture II for standby use; (4) Filling the mixture I of step (2) into a stainless steel mold and pressing it into a hollow cylinder, then filling the hollow cylinder with the mixture II of step (3), cold pressing and removing the mold to obtain a green body with the outer layer of the mixture I and the inner layer of the mixture II; (5) Place the green body of step (4) into a tubular furnace, and heat it to 200-300°C at a rate of 4-8°C / min under the conditions of a vacuum degree of 10-25 Pa and a continuous flow of 99.99% pure argon atmosphere. Keep the temperature for 240-300 min to complete thermal degreasing, and then cool it to room temperature with the furnace for use; (6) The green body after thermal degreasing in step (5) is placed in a graphite mold, placed in a spark plasma sintering furnace, evacuated to 4~6 Pa, heated to 550~650℃ at a heating rate of 80~90℃ / min, then heated to 850~900℃ at a heating rate of 90~110℃ / min, and finally heated to 1100~1200℃ at a heating rate of 40~50℃ / min, kept at this temperature for 8~12 minutes to complete spark plasma sintering, and then cooled to room temperature with the furnace to obtain Ti6Al4V5Cu medical titanium alloy with dense surface and porous interior.

2. The method for preparing a medical titanium alloy with a dense surface and porous interior according to claim 1, characterized in that: The chemical composition of the spherical Ti6Al4V5Cu titanium alloy powder in step (1) is as follows: Al: 5.50~6.50wt.%, V: 3.50~4.50wt.%, Cu: 4.50~6.0wt.%, Fe: ≤0.25wt.%, C: ≤0.08wt.%, N: ≤0.03wt.%, H: ≤0.008wt.%, O: ≤0.13wt.%, and the balance is Ti.

3. The method for preparing a medical titanium alloy with a dense surface and porous interior according to claim 1, characterized in that: The spherical Ti6Al4V5Cu titanium alloy powder in step (1) is prepared by electrode induction melting and inert gas atomization method.

4. The method for preparing a medical titanium alloy with a dense surface and porous interior according to claim 1, characterized in that: The pressing process of step (4) is unidirectional pressing, the pressing rate is 1-3 kN / min, the pressure is 45-50 kN, and the holding time is 25-30 min.

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