A biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure and a preparation method and application thereof

Abstract

This invention belongs to the field of materials technology, specifically relating to a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure, its preparation method, and its applications. This invention constructs a nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure on the surface of pure titanium or titanium alloys. Specifically, its interior contains micron-sized macropores, while its pore walls contain numerous submicron to nano-sized micropores. The framework material is nanocrystalline, thereby achieving a synergistic enhancement of the bioactivity and adjustment of the elastic modulus of the Ti-Mg alloy through porous structures of different scales. Simultaneously, the nanocrystalline structure strengthens the mechanical properties of the porous coating. Ti acts as the framework, providing mechanical support, while Mg serves as the bioactive and micro / nano-porous material. When the Ti-Mg composite material is implanted into the human body, Mg gradually degrades, which can improve the material's bioactivity (inducing new bone formation).

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure, its preparation method, and its application. Background Technology

[0002] Biomedical metallic materials are the most commonly used materials for hard tissue repair and replacement due to their high mechanical strength, good mechanical properties, and machinability. Titanium alloys, with their low density, high specific strength, good corrosion resistance, and biocompatibility, are among the most attractive biometallic materials currently available. However, the following two shortcomings limit their clinical application performance: ① Titanium alloys are bioinert materials with poor bioactivity and cannot actively induce phosphate deposition on their surface. Therefore, the implant and human bone are only simply mechanically bonded rather than strongly chemically bonded, resulting in poor implant stability and a longer osseointegration time. ② Titanium alloys have a high elastic modulus, which can cause a "stress shielding" phenomenon in the implant. The elastic modulus of human bone tissue is usually between 0.3 and 30 GPa, while the elastic modulus of Ti and titanium alloys is generally between 50 and 114 GPa. Therefore, the elastic modulus of medical titanium alloy materials does not match that of human bone tissue. It is difficult for the load to be transferred from the implant to the adjacent bone tissue, which makes it difficult for the bone tissue to be exercised, and it gradually shrinks. This causes the implant to loosen from the surrounding bone tissue, eventually leading to implantation failure, which is the phenomenon of "stress shielding".

[0003] Considering that biological tissues primarily interact with the atoms on the surface of titanium alloy implants, improving the surface bioactivity of titanium alloys could transform the bond between them and human bone from mechanical intercalation to stable biological bonding, thereby promoting bone repair and remodeling. Therefore, surface coating biomodification of titanium alloys is an effective method to address their bioinertness and improve their bioactivity. Currently, depositing hydroxyapatite (HA) coatings on titanium alloy surfaces is a common method to enhance the surface bioactivity of titanium alloy materials. However, the significant difference in thermal expansion coefficients between HA and titanium alloys leads to substantial residual thermal stress in the material, making the coating prone to detachment. For example, the linear expansion coefficients of HA and Ti-6Al-4V are approximately 15 × 10⁻⁶. -6 K -1 and 8.8×10 -6 K -1 Thermal stress caused by the mismatch in coefficients of thermal expansion will concentrate at the interface between the coating and the substrate, resulting in poor bonding between the coating and the substrate; in addition, the release of broken particles from the brittle HA coating may also lead to clinical implantation failure. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure, its preparation method and application. The biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure provided by the present invention has high bioactivity, bonding strength and mechanical properties.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure. The titanium grains in the micro / nano porous Ti-Mg alloy coating are nanocrystalline. The coating has micron-scale pores and micro / nano-scale pores. The pore size of the micron-scale pores is 2–35 μm. The pore size of the micro / nano-scale pores is 0.1–2 μm. The micro / nano-scale pores exist on the pore wall surface of the micron-scale pores. The thickness of the micro / nano porous Ti-Mg alloy coating is 100–500 μm.

[0007] Preferably, the average porosity of the biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure is 10-35%.

[0008] Preferably, the atomic ratio of Ti to Mg in the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is (50-80):(20-50).

[0009] This invention also provides a method for preparing a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure as described in the above technical solution, comprising the following steps:

[0010] Ti powder and Mg powder are mixed and mechanically alloyed to obtain nanocrystalline Ti-Mg alloy powder; the nanocrystalline Ti-Mg alloy powder is a Ti-Mg supersaturated solid solution with a particle size of micrometers and a structure in which Ti and Mg elements are uniformly distributed.

[0011] The nanocrystalline Ti-Mg alloy powder is cold-sprayed onto the surface of a pure titanium or titanium alloy substrate to form a porous nanocrystalline Ti-Mg alloy coating with micron-level pores. Then, microwave high-temperature sintering and high-vacuum low-temperature sintering are performed sequentially to obtain a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure.

[0012] Preferably, the volume ratio of Ti powder to Mg powder is (50-90):(10-50).

[0013] Preferably, the mechanical alloying is performed by ball milling; the ball-to-material ratio of the ball milling is (5-15):1; the ball milling time is 5-48 hours; the ball milling speed is 150-350 rpm; a process control agent is added during the ball milling process; the process control agent is stearic acid; and the amount of the process additive added is 0.5-5 wt.%.

[0014] Preferably, the conditions for cold spraying include: the spraying gas is nitrogen, the accelerating gas pressure is 2.0-3.5 MPa, the powder feeding gas pressure is 2.5-4.0 MPa, the spraying temperature is 550-850℃, the powder feeding rate is 15-35 g / min, the spraying distance is 15-25 mm, and the spray gun moving speed is 10-50 mm / s.

[0015] Preferably, the protective gas for microwave high-temperature sintering is argon, the temperature is 600-800℃, and the holding time is 10-30 min; the vacuum pressure for high-vacuum low-temperature sintering is 10-100 Pa, the temperature is 350-550℃, and the holding time is 5-25 h.

[0016] The present invention also provides the application of the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure described in the above technical solution or the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure prepared by the preparation method described in the above technical solution in the preparation of medical implants.

[0017] The present invention also provides a medical implant comprising a pure titanium or titanium alloy substrate and a biomedical nanocrystalline Ti-Mg alloy coating having a micro / nano porous structure;

[0018] The biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure described in the above technical solution or the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure prepared by the preparation method described in the above technical solution.

[0019] This invention provides a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure. The titanium grains in the micro / nano porous Ti-Mg alloy coating are nanocrystalline. The coating has micron-scale pores and micro / nano-scale pores. The pore size of the micron-scale pores is 2–35 μm. The pore size of the micro / nano-scale pores is 0.1–2 μm. The micro / nano-scale pores exist on the pore wall surface of the micron-scale pores. The thickness of the micro / nano porous Ti-Mg alloy coating is 100–500 μm. This invention constructs a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure on the surface of a pure titanium or titanium alloy substrate. The coating contains micron-sized macropores internally, while its surface walls contain numerous submicron to nano-sized micropores. The porous structure and rough internal and external surfaces of the coating increase the contact area between the implant and human bone, facilitating osteoblast adhesion, proliferation, and differentiation. This promotes the ingrowth of new bone tissue into the pores, forming a stable biological fixation. Simultaneously, the interconnected channels facilitate the exchange of nutrients and metabolic waste, promoting rapid tissue repair and reconstruction, and accelerating the healing process. Furthermore, the porous structure reduces the surface elastic modulus of the titanium alloy implant, mitigating the "stress shielding" effect caused by its high elastic modulus. The micron-sized pore structure facilitates osteoblast conduction into the pores and attachment, while the nanoporous structure significantly promotes early osteoblast adhesion and growth, thereby strengthening the interfacial bond between the implant and bone tissue. Meanwhile, the Mg element in the Ti-Mg alloy gradually degrades and is reabsorbed in the human body environment, improving the bioinertness of Ti and enhancing the bioactivity of the Ti-Mg alloy. Furthermore, the dissolution of Mg on the material surface creates numerous open pores, facilitating the ingrowth of newly formed bone tissue into these pores, resulting in mechanical interlocking between the implant and bone. The micropores increase the interface connection area, reducing the average stress level at the interface, allowing the load to be uniformly and effectively transferred to the surrounding bone tissue, thus mitigating stress shielding. This achieves a synergistic enhancement of the bioactivity of the Ti-Mg composite material through porous structures of different scales, while simultaneously utilizing nanocrystals to strengthen the mechanical properties of the porous coating. Ti acts as the framework, providing mechanical support, while Mg serves as the bioactive and pore-forming material. After the Ti-Mg composite material is implanted in the human body, Mg gradually degrades, which on the one hand improves the material's bioactivity (inducing new bone formation), and on the other hand leaves numerous pores to facilitate the ingrowth of new bone tissue, while the Ti framework provides mechanical support throughout the process.

[0020] This invention also provides a method for preparing the biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure. First, Ti powder and Mg powder are mechanically alloyed by ball milling to obtain highly bioactive nanocrystalline Ti-Mg alloy powder. This alloy powder is a Ti(Mg) supersaturated solid solution with a micrometer-scale particle size and a structure in which Ti and Mg elements are uniformly distributed internally. Then, it is cold-sprayed onto the surface of a pure titanium or titanium alloy substrate. Based on the low-temperature characteristics of cold spraying and the difficult-to-deform characteristics of titanium alloy particles, a porous nanocrystalline Ti-Mg alloy coating with micrometer-scale pores is formed on the surface of the titanium substrate. Then, a two-stage composite sintering process of microwave high-temperature sintering and high-vacuum low-temperature sintering is performed. On the one hand, the microwave high-temperature sintering... Warm sintering enhances the mechanical properties of micron-sized porous nanocrystalline Ti-Mg alloy coatings and the bonding performance between the coating and the substrate. On the other hand, based on the principle of vacuum sublimation, high-vacuum low-temperature sintering allows for the controllable volatilization of solid Mg atoms (partially) at lower temperatures, thereby forming submicron to nano-sized pores on the surface of micron-sized pores. This enables the synergistic construction of biomedical nanocrystalline Ti-Mg alloy coatings with micro / nano porous structures on the surface of pure titanium or titanium alloy substrates. Simultaneously, the high activity of nanocrystals is utilized to diffuse and strengthen the bonding strength of the "internal" and "external" interfaces of the porous coating during the sintering process. Attached Figure Description

[0021] Figure 1 This is a SEM image of the Ti powder used in Example 1 of the present invention;

[0022] Figure 2 This is a SEM image of the Mg powder used in Example 1 of the present invention;

[0023] Figure 3 The image shows the XRD pattern of the Ti powder used in Example 1 of this invention.

[0024] Figure 4 The image shows the XRD pattern of the Mg powder used in Example 1 of this invention.

[0025] Figure 5 The above are XRD patterns of mixed powders of Ti powder and Mg powder with different volume ratios before ball milling in an embodiment of the present invention.

[0026] Figure 6 The graph shows the effect of ball milling time on the phase structure of Ti-40Mg (volume ratio) alloy powder.

[0027] Figure 7 The graph shows the effect of ball milling time on the grain size of Ti-40Mg (volume ratio) alloy powder.

[0028] Figure 8 This is a particle size distribution diagram of Ti-40Mg (volume ratio) alloy powder after ball milling for 20 hours.

[0029] Figure 9 The image shows the SEM surface morphology of Ti-40Mg (volume ratio) alloy powder after ball milling for 20 hours.

[0030] Figure 10 SEM cross-sectional morphology of Ti-40Mg (volume ratio) alloy powder after ball milling for 20 hours;

[0031] Figure 11 SEM image of the surface morphology of the porous nanocrystalline Ti-Mg alloy coating with micron-sized pores prepared in Example 1;

[0032] Figure 12 SEM image of the cross section of the porous nanocrystalline Ti-Mg alloy coating with micron-sized pores prepared in Example 1;

[0033] Figure 13 SEM image of the fracture surface of the nanocrystalline Ti-Mg alloy coating with micro / nano porous structure prepared in Example 1;

[0034] Figure 14 The images show the SEM surface morphology and cross-sectional morphology of the Ti-10Mg alloy powder after ball milling in Example 2 of this invention.

[0035] Figure 15 The graph shows the effect of ball milling time on the phase structure of Ti-10Mg (volume ratio) alloy powder.

[0036] Figure 16 The graph shows the effect of ball milling time on the grain size of Ti-10Mg (volume ratio) alloy powder.

[0037] Figure 17 The images show the cross-sectional morphology of the cold-spray deposited Ti-10Mg alloy coating and the SEM images of the fracture surface of the micro / nano porous nanocrystalline Ti-Mg alloy coating in Example 2 of this invention.

[0038] Figure 18 This is a graph showing the ball milling results of the Ti-Mg alloy powder in Comparative Example 1 of this invention;

[0039] Figure 19 This is a flowchart illustrating the preparation of a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure, as described in this embodiment of the invention.

[0040] Figure 20 This is a schematic diagram of a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure, as described in an embodiment of the present invention. Detailed Implementation

[0041] This invention provides a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure. The titanium grains in the micro / nano porous Ti-Mg alloy coating are nanocrystalline. The coating has micron-scale pores and micro / nano-scale pores. The pore size of the micron-scale pores is 2–35 μm. The pore size of the micro / nano-scale pores is 0.1–2 μm. The micro / nano-scale pores exist on the pore wall surface of the micron-scale pores. The thickness of the micro / nano porous Ti-Mg alloy coating is 100–500 μm.

[0042] In this invention, the titanium grains in the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure are nanocrystalline; the particle size of the nanocrystalline grains is preferably 20-80 nm, more preferably 50 nm; the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure has a structure of micron-scale pores and micro / nano-scale pores; the pore size of the micron-scale pores is 2-35 μm, preferably 5-30 μm; the pore size of the micro / nano-scale pores is 0.1-2 μm, preferably 0.5-1.5 μm.

[0043] In this invention, the average porosity of the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is preferably 10-35%, more preferably 15-30%.

[0044] In this invention, the atomic ratio of Ti to Mg in the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is preferably (50-80):(20-50), more preferably (55-70):(30-45).

[0045] In this invention, the thickness of the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is 100-500 μm, more preferably 200-300 μm.

[0046] In this invention, Ti acts as a framework providing mechanical support, while Mg serves as a bioactive and pore-forming substance. When the Ti-Mg composite material is implanted into the human body, Mg gradually degrades, which on the one hand improves the material's bioactivity (inducing new bone formation), and on the other hand leaves a large number of pores to facilitate the ingrowth of new bone tissue, while the Ti framework provides mechanical support throughout the process.

[0047] This invention also provides a method for preparing a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure as described in the above technical solution, comprising the following steps:

[0048] Ti powder and Mg powder are mixed and mechanically alloyed to obtain nanocrystalline Ti-Mg alloy powder; the nanocrystalline Ti-Mg alloy powder is a Ti-Mg supersaturated solid solution with a particle size of micrometers and a structure in which Ti and Mg elements are uniformly distributed inside.

[0049] The nanocrystalline Ti-Mg alloy powder is cold-sprayed onto the surface of a pure titanium or titanium alloy substrate to form a porous nanocrystalline Ti-Mg alloy coating with micron-level pores. Then, microwave high-temperature sintering and high-vacuum low-temperature sintering are performed sequentially to obtain a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure.

[0050] Unless otherwise specified, the present invention does not have special requirements on the source of the raw materials used in the preparation, and commercially available products well known to those skilled in the art can be used.

[0051] This invention involves mechanically alloying Ti powder and Mg powder to obtain nanocrystalline Ti-Mg alloy powder; the nanocrystalline Ti-Mg alloy powder is a Ti-Mg supersaturated solid solution with a particle size in the micrometer range and a structure in which Ti and Mg elements are uniformly distributed inside.

[0052] In this invention, the particle size of the Ti powder is preferably 25-65 μm, more preferably 30-50 μm; the particle size of the Mg powder is preferably 15-45 μm, more preferably 20-40 μm.

[0053] In this invention, the volume ratio of Ti powder to Mg powder is preferably (50-90):(10-50), more preferably (60-90):(10-40).

[0054] In this invention, the mechanical alloying is preferably ball milling; the ball-to-material ratio of the ball milling is preferably (5-15):1, more preferably (6-10):1; the ball milling time is preferably 5-48h, more preferably 10-30h; the ball milling speed is preferably 150-350rpm, more preferably 180-250rpm.

[0055] In this invention, the equipment used for ball milling is preferably a planetary ball mill; the ball milling is preferably carried out under inert gas protection; the inert gas is preferably nitrogen; a process control agent is preferably added during the ball milling process; the process control agent is preferably stearic acid; the amount of the process additive added is preferably 0.5-5 wt.%, more preferably 1-3 wt.%.

[0056] In this invention, the particle size of the nanocrystalline Ti-Mg alloy powder is in the micrometer range; the grain size of the nanocrystalline Ti-Mg alloy powder is preferably 20-100 nm, and the particle size is preferably 10-25 μm. The nanocrystalline Ti-Mg alloy powder is a supersaturated solid solution alloy powder in which Mg is dissolved in Ti. The powder particles are approximately spherical in shape and have a structure in which Ti and Mg are uniformly distributed inside.

[0057] As shown in the Ti-Mg binary phase diagram, the solid solubility between Ti and Mg is very low (below 500℃, the solid solubility of Mg in Ti is only 0.3 at.%, while the solid solubility of Ti in Mg is about 0.1 at.%). Furthermore, the boiling point of Mg is 1107℃, which is lower than the melting point of Ti (1680℃). Therefore, traditional smelting methods cannot be used to prepare Ti-Mg composite materials. This invention utilizes ball milling to mechanically alloy Ti and Mg powders. During ball milling, high-speed collisions cause severe plastic deformation of the Ti and Mg powder particles, generating numerous dislocations and other crystal defects within the material. This leads to a corresponding increase in lattice distortion and microstrain, forming high-density dislocations in high-strain regions. Dislocation rearrangement causes the original coarse grains to split into multiple subgrains with low-angle grain boundaries. These subgrains gradually refine and evolve into even finer grains, forming nanocrystalline Ti-Mg alloy powder. Grain refinement can significantly enhance cell viability and stem cell response speed on the surface of titanium implants, and accelerate stem cell adsorption on the Ti surface, osteoblast proliferation, and bone integration.

[0058] In this invention, the internal structure of the nanocrystalline Ti-Mg alloy powder is preferably a structure in which Ti and Mg are uniformly distributed.

[0059] Both Ti and Mg are metals with a certain degree of plastic deformation capability. During mechanical alloying, under the intense collision of the grinding balls, both Ti and Mg particles undergo strong plastic deformation and flattening. Simultaneously, they also "cold-weld" together to form a layered structure with an approximately alternating distribution of Ti and Mg. As the ball milling time increases, the thickness of these layered structures continuously decreases, and they diffuse and even alloy with each other, ultimately leading to the disappearance of the layered structure and the formation of a completely homogeneous alloy. For ductile metals, layered structures are an inevitable phenomenon during ball milling. The appearance of a fine layered structure indicates that the two powders have been completely homogenized through collision deformation and cold welding. It also indicates that the material grains are very small, even reaching nanocrystal size. This invention, by controlling the size of Mg in the Ti-Mg supersaturated solid solution, can obtain micro- and nano-scale pores during subsequent vacuum heat treatment through the in-situ solid-state sublimation of tiny Mg particles.

[0060] After obtaining the nanocrystalline Ti-Mg alloy powder, the present invention cold sprays the nanocrystalline Ti-Mg alloy powder onto the surface of a pure titanium or titanium alloy substrate to form a nanocrystalline Ti-Mg alloy coating with a micron-scale porous structure.

[0061] In this invention, the titanium alloy is preferably a β-type titanium alloy, more preferably a Ti-Mo titanium alloy or a Ti-Ta titanium alloy.

[0062] In this embodiment of the invention, the dimensions of the pure titanium or titanium alloy substrate are specifically 50mm × 25mm × 5mm.

[0063] Before the cold spraying, the present invention preferably sandblasts the surface of the pure titanium or titanium alloy substrate; the sandblasting is preferably performed using 24-mesh brown corundum; the sandblasting pressure is preferably 0.3-0.6 MPa, more preferably 0.4-0.5 MPa; the sandblasting time is preferably 10-30 s, more preferably 15-20 s.

[0064] In this invention, the surface roughness of the pure titanium or titanium alloy substrate after sandblasting is preferably Ra = 5 to 15 μm, more preferably Ra = 10 μm.

[0065] This invention removes impurities from the surface of a pure titanium or titanium alloy substrate by sandblasting and increases the surface roughness of the pure titanium or titanium alloy substrate, thereby improving the adhesion between the pure titanium or titanium alloy substrate and the coating.

[0066] In this invention, the conditions for cold spraying include: the spraying gas is preferably nitrogen, the accelerating gas pressure is preferably 2.0-3.5 MPa, more preferably 2.5-3 MPa, the powder feeding gas pressure is preferably 2.5-4.0 MPa, more preferably 3.0-3.5 MPa, the spraying temperature is preferably 550-850℃, more preferably 550-750℃, the powder feeding rate is preferably 15-35 g / min, more preferably 20-25 g / min, the spraying distance is preferably 15-25 mm, more preferably 20-25 mm, and the spray gun moving speed is preferably 10-50 mm / s, more preferably 10-30 mm / s.

[0067] In this invention, the thickness of the nanocrystalline Ti-Mg alloy coating with a micron-scale porous structure is preferably 0.1–0.5 mm, more preferably 0.2–0.3 mm; the porosity of the nanocrystalline Ti-Mg alloy coating with a micron-scale porous structure is preferably 5–35%, more preferably 5–25%; and the pore size of the nanocrystalline Ti-Mg alloy coating with a micron-scale porous structure is preferably 5–45 μm, more preferably 10–30 μm.

[0068] This invention involves cold spraying nanocrystalline Ti-Mg alloy powder onto the surface of a pure titanium or titanium alloy substrate to form a porous nanocrystalline Ti-Mg alloy coating with micron-scale pores. Since the powder temperature is much lower than the melting point of the material, cold spraying avoids problems such as grain growth, melting and oxidation caused by heating, and can achieve "in-situ transplantation" of the original powder structure.

[0069] After obtaining the nanocrystalline Ti-Mg alloy coating with micron-level porous structure, the present invention sequentially performs microwave high-temperature sintering and high-vacuum low-temperature sintering on the nanocrystalline Ti-Mg alloy coating with micro / nano porous structure to obtain a biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure.

[0070] In this invention, the protective gas for microwave high-temperature sintering is preferably argon, the purity of which is preferably ≥99.99%, more preferably 99.999%, the temperature is preferably 600-800℃, more preferably 650-750℃, the holding time is preferably 10-30 min, more preferably 15-25 min, and the heating rate to the microwave high-temperature sintering temperature is preferably 10℃ / s.

[0071] In this invention, the vacuum pressure of the high-vacuum low-temperature sintering is preferably 10-100 Pa, more preferably 20-50 Pa, the temperature is preferably 350-550℃, more preferably 450-550℃, the holding time is preferably 5-25 h, more preferably 5-15 h, and the heating rate to the high-vacuum low-temperature sintering temperature is preferably 15℃ / s.

[0072] This invention improves the mechanical properties of micron-sized porous nanocrystalline Ti-Mg alloy coatings and the bonding performance between the coating and the substrate through microwave high-temperature sintering; through high-vacuum low-temperature sintering, based on the principle of vacuum sublimation, the controllable volatilization of solid Mg atoms can be achieved at a lower temperature, thereby forming submicron to nano-sized pores on the pore wall surface of micron-sized pores.

[0073] Compared to dense coatings, porous coatings, with their porous structure and rough inner and outer surfaces, increase the contact area between the implant and human bone. This promotes osteoblast adhesion, proliferation, and differentiation, thereby facilitating the ingrowth of new bone tissue into the pores to form a stable biological fixation. Simultaneously, the interconnected channels facilitate the flow and exchange of nutrients and metabolic waste, promoting rapid tissue repair and reconstruction and accelerating the healing process. Furthermore, the porous structure reduces the surface elastic modulus of the titanium alloy implant, thus mitigating the "stress shielding" effect caused by its excessively high elastic modulus. This invention utilizes high-vacuum, low-temperature sintering to sublimate a portion of the Mg on the surface of a porous nanocrystalline Ti-Mg alloy coating, forming micropores with micro / nano-scale pores. This results in a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure. The micron-sized pores facilitate the conduction of osteoblasts into the pores and their attachment, while the nano-sized pores significantly promote early adhesion and growth of osteoblasts. This achieves a synergistic enhancement of the bioactivity and biocompatibility of the Ti-Mg composite material by porous structures of different scales, thereby strengthening the interfacial bonding strength between the implant and bone tissue. Simultaneously, the nanocrystals are used to enhance the mechanical properties of the porous coating.

[0074] Nanocrystalline structures endow materials with higher elastic modulus and activity. Therefore, without the need for pore-forming agents, a porous nanocrystalline Ti-Mg alloy coating with a "natural" micron-scale pore structure can be obtained by depositing a coating on the surface of a titanium alloy using ball-milled nanocrystalline Ti-Mg composite powder as raw material and employing cold spraying technology. Sintering heat treatment can significantly improve the bonding strength of the porous nanocrystalline Ti-Mg alloy coating formed by cold spraying and can control the pore structure and porosity. Based on the principle of vacuum sublimation, the porous nanocrystalline Ti-Mg alloy coating can be subjected to high-vacuum low-temperature sintering treatment over a wide temperature range, achieving controlled volatilization of solid Mg atoms (partially), thereby forming nanoscale pores within the coating.

[0075] This invention proposes a composite process of cold spraying and high-vacuum low-temperature sintering to prepare a micro / nano-porous nanocrystalline Ti-Mg alloy coating. This process creates "nanopores" in situ on the pore walls of the porous Ti-Mg composite material and controls the aggregation and growth of these nanopores, thereby constructing a micro / nano-porous nanocrystalline Ti-Mg alloy coating on the surface of a titanium substrate. Simultaneously, based on the high diffusivity of nanocrystals, the bonding between the nanocrystalline Ti-Mg alloy coating and the titanium alloy substrate, as well as between particles within the coating, can be strengthened, thereby improving the mechanical properties of the porous coating.

[0076] The present invention also provides the application of the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure described in the above technical solution or the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure prepared by the preparation method described in the above technical solution in the preparation of medical implants.

[0077] The present invention also provides a medical implant comprising a pure titanium or titanium alloy substrate and a biomedical nanocrystalline Ti-Mg alloy coating having a micro / nano porous structure;

[0078] The biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure described in the above technical solution or the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure prepared by the preparation method described in the above technical solution.

[0079] In this invention, the titanium alloy is preferably a β-type titanium alloy.

[0080] Figure 19 This is a flowchart illustrating the preparation of a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nanoporous structure, as described in an embodiment of the present invention. Figure 19 As can be seen, this invention obtains Ti-Mg supersaturated solid solution nanocrystalline powder by mechanically alloying pure titanium powder and pure magnesium powder, with Ti and Mg elements uniformly distributed inside. Then, the alloy powder obtained by mechanical alloying is deposited with a porous coating by cold spraying to obtain a porous nanocrystalline Ti-Mg alloy coating with micron-level pores. Finally, a nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is obtained by composite sintering of microwave high-temperature sintering and vacuum sintering. Among them, microwave high-temperature sintering can improve the mechanical properties of nanocrystalline Ti-Mg alloy coating and the bonding performance between coating and substrate, while vacuum sintering forms submicron to nano-level pores on the surface of micron-level pores.

[0081] Figure 20 This is a schematic diagram of a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure, as described in an embodiment of the present invention. Figure 20 As shown, the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is composed of nano-Ti-Mg alloy, micron-scale pores, submicron-scale and nano-scale pore structures inside the coating, and the pore walls of the nanocrystalline Ti-Mg alloy particles contain nanopores and submicron-scale pores.

[0082] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0083] Example 1

[0084] Ti powder (particle size 25-65 μm) and Mg powder (particle size 15-45 μm) were selected according to a volume ratio of 60:40 and placed in a planetary ball mill for mechanical alloying under nitrogen protection. The ball-to-material ratio was 10:1, the ball milling time was 30 h, the rotation speed was 180 rpm, and the amount of stearic acid added was 1.5 wt.%, to obtain nanocrystalline Ti-Mg alloy powder with an internal layered structure thickness of 0.5-5 μm.

[0085] The nanocrystalline Ti-Mg alloy powder was deposited onto the surface of a titanium alloy (50mm×25mm×5mm) by cold spraying. Before spraying, the titanium alloy surface was treated with 24-mesh brown corundum sandblasting at a pressure of 0.4MPa for 20s. The surface roughness of the titanium substrate after sandblasting was Ra=10μm. The cold spraying conditions were: nitrogen as the spraying gas, accelerating gas pressure of 2.5MPa, powder feed gas pressure of 3.0MPa, spraying temperature of 550℃, powder feed rate of 25g / min, spraying distance of 25mm, and spray gun moving speed of 10mm. The coating thickness is approximately 0.25 mm, the porosity is between 10 and 15%, and the pore size is between 10 and 25 μm, forming a nanocrystalline Ti-Mg alloy coating with a micron-scale porous structure. Then, the temperature is raised to 680 °C at a rate of 10 °C / s and microwave high-temperature sintering is performed for 30 min under the protection of 99.999% pure argon gas. After that, the temperature is raised to 450 °C at a rate of 15 °C / s under 100 Pa and high-vacuum low-temperature sintering is performed for 5 h. After cooling to room temperature in the furnace, a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure is obtained.

[0086] The coating has a micron-scale pore size range of 10–35 μm, a micro-nano pore size range of 0.1–2 μm, and an average porosity of 25–30%.

[0087] Example 2

[0088] The difference from Example 1 is that the volume ratio of Ti powder to Mg powder is 90:10, while the rest is the same as Example 1.

[0089] Example 3

[0090] The difference from Example 1 is that the spraying temperature is 750°C, but the rest is the same as Example 1.

[0091] A cold-spray deposited Ti-40Mg alloy coating has a porosity between 5% and 8%, with pore sizes between 5 and 10 μm, forming a nanocrystalline Ti-Mg alloy coating with a micron-scale porous structure. After a two-stage heat treatment, a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure was obtained, with a micron-scale pore size range of 2–5 μm, a micro / nano pore size range of 0.1–1 μm, and an average porosity of 10–15%.

[0092] Example 4

[0093] The difference from Example 1 is that after microwave high-temperature sintering at 750°C at a rate of 10°C / s for 30 min, the temperature is then increased to 550°C at a rate of 15°C / s under 50 Pa for high-vacuum low-temperature sintering for 25 h. The rest of the process is the same as in Example 1.

[0094] After two-stage heat treatment, a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure was obtained. The micron-scale pore size range is 15–30 μm, the micro / nano pore size range is 0.5–2 μm, and the average porosity is 30–35%.

[0095] Comparative Example 1

[0096] The difference from Example 1 is that the volume ratio of Ti powder to Mg powder is 30:70, while the rest is the same as Example 1.

[0097] Comparative Example 2

[0098] The difference from Example 1 is that the accelerating gas pressure is 1.5 MPa and the spraying temperature is 500°C during the cold spray coating process. All other aspects are the same as in Example 1.

[0099] The hardness of the Ti-Mg alloy powder after ball milling will increase significantly to about 490HV0.025 (the initial Ti powder is about 130HV0.025). This results in limited collision deformation of the powder under the cold spraying parameters. Most of the powder will bounce back from the collision, and at the same time, it will compact and densify the small amount of particles that have been deposited, making it difficult to prepare a porous coating of a certain thickness.

[0100] Performance testing

[0101] (1) The surface morphology of the Ti powder and Mg powder used in Example 1 of this invention was tested using SEM (scanning electron microscopy) energy dispersive spectroscopy (EDS). The results are as follows: Figures 1-2 As shown.

[0102] Depend on Figure 1 It can be seen that the powder is prepared by melting and crushing and has a polygonal shape.

[0103] Depend on Figure 2 It can be seen that the powder is prepared by gas atomization and has an approximately perfect spherical shape.

[0104] (2) The Ti powder used in Example 1 of this invention was tested using X-ray diffraction technology, and the results are as follows: Figure 3 As shown.

[0105] Depend on Figure 3It can be seen that the powder phase structure is a single α-Ti phase, with no other phases present.

[0106] (3) The Mg powder used in Example 1 of this invention was tested using X-ray diffraction technology, and the results are as follows: Figure 4 As shown.

[0107] Depend on Figure 4 It can be seen that the powder phase structure is a single Mg phase, with no other phases present.

[0108] (4) X-ray diffraction was used to test mixed powders of Ti powder and Mg powder with different volume ratios before ball milling. The results are as follows: Figure 5 As shown.

[0109] Depend on Figure 5 It can be seen that the Ti / Mg mixed powder is composed of Ti phase and Mg phase, and as the volume fraction of Mg increases, the intensity of the Mg main peak in the XRD pattern of the mixed powder also increases continuously.

[0110] (5) X-ray diffraction was used to test Ti-40Mg (volume ratio) alloy powders obtained with different ball milling times. The results are as follows: Figure 6 As shown.

[0111] Depend on Figure 6 It can be seen that as the ball milling time increases, the Ti-40%Mg alloy powder after ball milling is still composed of Ti phase and Mg phase, with no other phases generated. At the same time, the continuous broadening of the diffraction peak of Ti indicates that the grain size of the alloy powder after ball milling is continuously decreasing, while the main diffraction peak of Mg is continuously decreasing, indicating that Mg continuously dissolves into the Ti lattice during the ball milling process to form a supersaturated metastable solution alloy.

[0112] (6) The effect of ball milling time on the grain size of Ti-40Mg (volume ratio) alloy powder, as follows: Figure 7 As shown.

[0113] Depend on Figure 7 It can be seen that as the ball milling time is extended, the grain size of the alloy powder after ball milling decreases rapidly in the initial stage (before 12h), and then decreases slowly and remains at around 20nm.

[0114] (7) The effect of ball milling for 20 hours on the particle size distribution of Ti-40Mg (volume ratio) alloy powder as follows: Figure 8 As shown.

[0115] Depend on Figure 8 It can be seen that the Ti-40Mg alloy powder after ball milling has a concentrated particle size distribution with a median diameter of about 20 μm, and the powder size meets the requirements of the coating deposition technology of cold spraying.

[0116] (8) The SEM surface morphology of Ti-40Mg (volume ratio) alloy powder after ball milling for 20 hours is shown in the figure. Figure 9 As shown.

[0117] Depend on Figure 9 It can be seen that the Ti-40Mg alloy powder after ball milling has a particle shape that is approximately spherical and has good flowability. The powder shape meets the requirements of the cold spray coating technology.

[0118] (9) The SEM cross-sectional morphology of Ti-40Mg (volume ratio) alloy powder after ball milling for 20 hours is shown in the figure. Figure 10 As shown.

[0119] Depend on Figure 10 It can be seen that the gray area inside the cross-section of the ball-milled Ti-40Mg alloy powder is a solid solution region in which Ti and Mg are evenly distributed, and there is a fine Ti and Mg layered structure. The internal microstructure of the powder meets the requirements for the in-situ formation of micro-nano pores by subsequent heat treatment.

[0120] (10) The surface morphology of the porous nanocrystalline Ti-Mg alloy coating with micron-sized pores prepared in Example 1 was tested using SEM (scanning electron microscopy) energy dispersive spectroscopy (EDS). The results are as follows: Figure 11 As shown.

[0121] Depend on Figure 11 It can be seen that the surface of the cold-sprayed Ti-Mg alloy coating is relatively rough and the bonding between the particle interfaces is strong. Due to the high elastic modulus of Ti alloy, the powder particles do not deform sufficiently during the deposition process, and there are a large number of micron-sized pores between the particles, thus achieving the purpose of obtaining a micron-sized porous Ti-Mg alloy coating through cold spraying.

[0122] (11) The cross-section of the porous nanocrystalline Ti-Mg alloy coating with micron-sized pores prepared in Example 1 was tested using SEM (scanning electron microscopy) energy dispersive spectroscopy. The results are as follows: Figure 12 As shown.

[0123] Depend on Figure 12 It can be seen that there are a large number of micron-sized pores inside the cold-sprayed Ti-Mg alloy coating.

[0124] (12) The fracture surface of the nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure prepared in Example 1 was tested using SEM (scanning electron microscopy) energy dispersive spectroscopy. The results are as follows: Figure 13 As shown.

[0125] Depend on Figure 13 It is known that the vacuum sublimation and volatilization of Mg within the Ti-Mg alloy particles inside the coating creates a large number of submicron and even nanoscale micropores. This ultimately results in a Ti-Mg alloy coating with a micro / nano porous structure.

[0126] (13) Figure 14 The images show the SEM surface morphology and cross-sectional morphology of the Ti-10Mg alloy powder after ball milling in Example 2 of this invention. Figure 15 The graph shows the effect of ball milling time on the phase structure of Ti-10Mg (volume ratio) alloy powder. Figure 16 The graph shows the effect of ball milling time on the grain size of Ti-10Mg (volume ratio) alloy powder. Figure 17 The images show the cross-sectional morphology of the cold-spray deposited Ti-10Mg alloy coating in Example 2 of this invention and the SEM images of the fracture surface of the nanocrystalline Ti-Mg alloy coating with micro / nano porous structure.

[0127] Depend on Figures 14-17 It can be seen that the Ti-10Mg alloy powder after ball milling has an approximately spherical particle surface morphology with a particle size of 10–15 μm. The Ti / Mg layered structure inside the cross-section of the alloy powder is highly refined, and the Ti and Mg elements are basically uniformly distributed. With the extension of ball milling time, the diffraction peak of Mg in the Ti-10Mg alloy powder completely disappears, thus obtaining a Ti(Mg) supersaturated solid solution alloy powder. Its grain size does not decrease significantly with the extension of ball milling time. After ball milling for 30 hours, the grain size of the powder is about 15 nm. The cross-sectional morphology of the cold-spray deposited Ti-10Mg alloy coating is shown in the figure. The coating porosity is between 25% and 30%, and the pore size is between 15 and 35 μm, forming a nanocrystalline Ti-Mg alloy coating with a micron-scale porous structure. After undergoing a two-stage heat treatment, the above coating was obtained as a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure. The micron-scale pore size range is 15–30 μm, the micro / nano pore size range is 0.1–1 μm, and the average porosity is 30–35%.

[0128] (14) Figure 18 The image shows the ball milling results of the Ti-Mg alloy powder in Comparative Example 1 of this invention.

[0129] Depend on Figure 18 It is known that during the ball milling process, almost all the powder is cold-welded to the inner wall of the ball mill jar and the surface of the grinding balls, making it impossible to obtain Ti-Mg alloy powder. Therefore, it is also impossible to carry out subsequent coating preparation and heat treatment.

[0130] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure, characterized in that, The titanium grains in the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure are nanocrystalline; the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure has a structure with micron-scale pores and micro / nano-scale pores; the pore size of the micron-scale pores is 10-35µm; The pore size of the micro / nano-scale pores is 0.1–2 µm; The micro / nano-scale pores exist on the pore wall surface of the micron-scale pores; the thickness of the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is 100–500 µm, and the preparation method of the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure includes the following steps: Ti powder and Mg powder are mixed and mechanically alloyed to obtain nanocrystalline Ti-Mg alloy powder; the nanocrystalline Ti-Mg alloy powder is a Ti-Mg supersaturated solid solution with a particle size of micrometers and a structure in which Ti and Mg elements are uniformly distributed. The nanocrystalline Ti-Mg alloy powder is cold-sprayed onto the surface of pure titanium or titanium alloy substrate to form a porous nanocrystalline Ti-Mg alloy coating with micron-level pores. Then, microwave high-temperature sintering and high-vacuum low-temperature sintering are performed sequentially to obtain a biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure. The protective gas for microwave high-temperature sintering is argon, the temperature is 600-800℃, and the holding time is 10-30 min; the vacuum pressure for high-vacuum low-temperature sintering is 10-100 Pa, the temperature is 350-550℃, and the holding time is 5-25 h.

2. The biomedical nanocrystalline Ti-Mg alloy coating according to claim 1, characterized in that, The average porosity of the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is 10–35%.

3. The biomedical nanocrystalline Ti-Mg alloy coating according to claim 1, characterized in that, The atomic ratio of Ti to Mg in the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is (50-80):(20-50).

4. The method for preparing the biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Ti powder and Mg powder are mixed and mechanically alloyed to obtain nanocrystalline Ti-Mg alloy powder; the nanocrystalline Ti-Mg alloy powder is a Ti-Mg supersaturated solid solution with a particle size of micrometers and a structure in which Ti and Mg elements are uniformly distributed. The nanocrystalline Ti-Mg alloy powder is cold-sprayed onto the surface of pure titanium or titanium alloy substrate to form a porous nanocrystalline Ti-Mg alloy coating with micron-level pores. Then, microwave high-temperature sintering and high-vacuum low-temperature sintering are performed sequentially to obtain a biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure. The volume ratio of Ti powder to Mg powder is (50-90):(10-50); The conditions for cold spraying include: the spraying gas is nitrogen, the accelerating gas pressure is 2.0-3.5 MPa, the powder feeding gas pressure is 2.5-4.0 MPa, the spraying temperature is 550-850℃, the powder feeding rate is 15-35 g / min, the spraying distance is 15-25 mm, and the spray gun moving speed is 10-50 mm / s.

5. The preparation method according to claim 4, characterized in that, The mechanical alloying is performed by ball milling; the ball-to-material ratio of the ball milling is (5-15):1; the ball milling time is 5-48 hours; the ball milling speed is 150-350 rpm; a process control agent is added during the ball milling process; the process control agent is stearic acid; the amount of the process control agent added is 0.5-5 wt.%.

6. The application of the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure as described in any one of claims 1 to 3, or the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure prepared by the preparation method described in any one of claims 4 to 5, in the preparation of medical implants.

7. A medical implant, characterized in that, Including a pure titanium or titanium alloy substrate and a biomedical nanocrystalline Ti-Mg alloy coating with a micro / nano porous structure; The biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure is the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure according to any one of claims 1 to 3, or the biomedical nanocrystalline Ti-Mg alloy coating with micro / nano porous structure prepared by the preparation method according to any one of claims 4 to 5.

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