A bio-adaptive surface composite modification method for beta titanium alloy

Abstract

This invention provides a biocompatible β This invention relates to a method for composite modification of titanium alloy surfaces, belonging to the technical field of alloy modification methods. The invention includes applications in medical... β This invention involves introducing bioactive particles onto the surface of a titanium alloy substrate, performing friction stir processing (FSP) on the substrate to introduce bioactive particles and construct a gradient grain structure, and then subjecting the FSP-treated substrate to compressed plasma flow (CPF) treatment to achieve uniform distribution of bioactive particles and construct a topology with an average surface roughness of 3-6 μm suitable for cell growth. The invention precisely controls the amount of bioactive particles introduced and constructs a gradient grain structure through friction stir processing (FSP); simultaneously, compressed plasma flow (CPF) technology achieves uniform distribution of bioactive particles and an ideal surface roughness of 3-6 μm on the titanium alloy surface. Ultimately, this significantly improves the cell adhesion, proliferation capacity, and osteogenic properties of the material surface, solving the technical problem of low integration efficiency of traditional titanium alloy implants with human bone tissue.

Description

Technical Field

[0001] This invention relates to the field of alloy modification methods, and more particularly to a biocompatible method. β A composite modification method for titanium alloy surfaces. Background Technology

[0002] In orthopedic clinical treatment, the biocompatibility of implant materials directly affects treatment effectiveness and implant lifespan. The elastic modulus of human bone tissue is approximately 10-30 GPa. Although traditional medical titanium alloys (such as Ti-6Al-4V) have good corrosion resistance and mechanical strength, their elastic modulus (approximately 110 GPa) differs significantly from that of human bone tissue, easily inducing a "stress shielding effect." This can lead to absorption and loosening of the bone tissue surrounding the implant, ultimately requiring a secondary surgery for removal.

[0003] Ti35Nb2Ta3Zr (TNTZ) β Titanium alloys, as a novel medical-grade titanium alloy, have an elastic modulus (approximately 50-60 GPa) closer to that of human bone tissue and are free of toxic elements such as aluminum and vanadium, resulting in higher biocompatibility and making them an increasingly ideal material for orthopedic implants. However, TNTZ titanium alloys have a bioinert surface, lacking bioactive sites that promote cell adhesion, proliferation, and osteogenic differentiation, and their surface topology is unfavorable for cell growth, leading to slower integration with bone tissue and limiting their widespread clinical application.

[0004] To overcome the challenge of bioinertness on the surface of medical titanium alloys, surface modification technology has become a hot research topic. Introducing bioactive elements and constructing optimized topologies on the material surface can significantly improve its biocompatibility. Currently, titanium alloy surface modification technologies mainly include bioactive coating preparation, ion implantation, machining modification, and plasma treatment. Among these, friction stir processing (FSP) and compressed plasma flow (CPF) technologies have received widespread attention in the field of metallic material surface modification due to their unique advantages.

[0005] The conventional modification methods in the prior art are as follows: (1) Friction Stir Processing (FSP) Modification Technology: The surface of TNTZ titanium alloy is treated by FSP process, which uses thermomechanical action to refine the surface grains. At the same time, bioactive particles such as Zn and Mg can be introduced during the processing to improve the bioactivity of the material surface. For example, related studies have shown that by filling the grooves on the surface of titanium alloy with Zn powder, FSP processing can introduce Zn element and refine grains, which can improve the cell compatibility of the material to a certain extent.

[0006] (2) Compressed Plasma Flow (CPF) Modification Technology: By utilizing the high energy density of CPF, the surface of titanium alloy is etched and activated to change the surface roughness and surface energy, thereby constructing a topological structure that is conducive to cell adhesion. For example, by adjusting the CPF process parameters, a micron-level rough structure is formed on the surface of titanium alloy, which improves the initial adhesion ability of cells to the material surface.

[0007] However, existing technologies have the following drawbacks: (1) Friction Stir Processing (FSP) Modification Technology: FSP processing mainly achieves plastic deformation and element doping of materials through the mechanical action of the stirring head. Although it can introduce bioactive ions such as Zn and refine grains, it is difficult to form a uniform and controllable microstructure on the material surface. The surface roughness after processing is low (usually less than 2 μm), and Zn ions are unevenly distributed on the surface, with some areas showing agglomeration. This results in uneven distribution of cell adhesion sites, which cannot fully exert the role of bioactive elements, and the improvement in osteogenic performance is limited.

[0008] (2) Compressed Plasma Flow (CPF) Modification Technology: CPF technology can effectively control the surface roughness of titanium alloys and construct optimized topological structures, but it is difficult to achieve the stable introduction of bioactive ions such as Zn. The modified surface only relies on physical morphology to improve cell adhesion, lacks the chemical stimulation of bioactive elements, and is difficult to effectively promote long-term cell proliferation and osteogenic differentiation. The integration strength between the material and bone tissue is not significantly improved.

[0009] (3) Common problems of other existing modification technologies: Bioactive coating preparation technology (such as hydroxyapatite coating) has problems such as weak bonding between coating and substrate and easy peeling; Although ion implantation technology can introduce active elements, the implantation depth is shallow (only nanometer level), and the active elements are easily lost during long-term use, and it cannot change the macroscopic topological structure of the material surface.

[0010] (4) Problems with composite modification technology: Some studies have attempted to combine two or more single modification technologies, but have failed to achieve synergistic optimization of process parameters, making it difficult to simultaneously meet the needs of comprehensive improvement in mechanical compatibility, cell compatibility and osteogenic performance. Summary of the Invention

[0011] In view of this, in order to solve the existing β Addressing the technical problems of insufficient bioactivity on titanium alloy surfaces and the need to improve cell adhesion and osteogenic properties, this invention provides a biocompatible... βA composite modification method for titanium alloy surfaces was developed, establishing a synergistic and controllable modification approach that integrates micro / nano structures with bioactive elements. Friction stir processing (FSP) was used to precisely control the introduction of bioactive particles and construct a gradient grain structure. Simultaneously, compressed plasma flow (CPF) technology was employed to achieve uniform distribution of bioactive particles and an ideal surface roughness of 3-6 μm on the titanium alloy surface. Ultimately, this significantly improved the cell adhesion, proliferation capacity, and osteogenic properties of the material surface, solving the technical challenge of low integration efficiency between traditional titanium alloy implants and human bone tissue.

[0012] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a biocompatible β A method for composite modification of titanium alloy surfaces, characterized by comprising the following steps: Step (1), pre-treated medical β A continuous groove structure is machined on the surface of a titanium alloy substrate, and bioactive particles are introduced. Step (2): The substrate treated in step (1) is subjected to friction stirring to introduce bioactive particles into the surface layer of the substrate and to construct a gradient grain structure. Step (3): The substrate after step (2) is subjected to compressed plasma flow treatment to make the bioactive particles uniformly distributed on the surface of the substrate and to construct a topology with an average surface roughness of 3-6 μm suitable for cell growth.

[0013] Preferably, in step (2), the friction stir processing parameters are as follows: The stirring head has a forward speed of 50-100 mm / min, a rotation speed of 150 r / min-300 r / min, and a downward pressure of 0.05-0.2 mm.

[0014] Preferably, in step (2), during friction stirring, the structural parameters of the stirring head are as follows: The shoulder diameter is 16mm, and the bottom diameter, top diameter and length of the truncated cone-shaped needle are 6mm and 4mm respectively.

[0015] Preferably, in step (3), the compressed plasma flow processing parameters are as follows: The capacitor energy storage device has a capacity of 1000-1500mF and an initial operating voltage of 2-6 kV; the plasma flow pulse duration is 50-200 μs, the pulse interval is about 3-10 s, and a total of three pulse processes are performed; the plasma flow velocity is (4-8)×10 6 cm / s, electron concentration is (3-8)×10 17 cm -3 The working distance between the sample and the plasma outlet is 8-16 cm.

[0016] Preferably, in step (3), the compressed plasma flow treatment is carried out under a nitrogen atmosphere of 400 Pa.

[0017] Preferably, in step (2), the surface ultrafine grain size of the gradient grain structure is 1-2 μm, gradually increasing towards the interior.

[0018] Preferably, the bioactive particles are Zn nanoparticles.

[0019] Preferably, the Zn nanoparticles have a particle size of 50-100 nm and a packing density of 1.2 g / cm³. 3 .

[0020] Preferably, in the groove structure, the groove depth is 1mm, the width is 1mm, the groove spacing is 2mm, and the groove direction is consistent with the friction stirring processing direction.

[0021] Preferably, in step (1), the preprocessing is as follows: First, the medical β-titanium alloy substrate is mechanically polished with sandpaper to remove surface oxide scale and impurities; then, it is ultrasonically cleaned with anhydrous ethanol to remove surface oil; finally, it is dried and ready for use.

[0022] Compared with the prior art, the present invention has the following beneficial effects: Synergistic Enhancement of Biocompatibility: This invention utilizes a composite process of friction stir processing (FSP) and compressed plasma flow (CPF) to synergistically regulate the introduction of bioactive particles and the construction of surface topology: The FSP process stably introduces Zn bioactive ions into the surface of Ti-35Nb-2Ta-3Zr (TNTZ) titanium alloy, providing chemical stimulation for cell growth; the CPF process precisely constructs a surface topology with an average roughness of 3-6 μm, increasing the contact area and adhesion sites between cells and materials, and further dispersing Zn particles that may aggregate during the FSP process, so that the active elements are evenly distributed on the surface layer, significantly improving cell compatibility.

[0023] Simultaneous optimization of osteogenic performance and mechanical compatibility: This invention constructs a gradient grain structure (the surface ultrafine grain size is 1-2μm, gradually increasing towards the interior) through the FSP process, making the surface mechanical properties of titanium alloy more compatible with human bone tissue and avoiding the "stress shielding effect"; at the same time, the CPF process achieves uniform distribution of Zn ions, ensuring their continuous release to promote osteoblast differentiation and bone matrix secretion. The optimized surface topology provides physical guidance for bone tissue growth, accelerates the integration of implants with bone tissue, and significantly improves osteogenic performance.

[0024] Improved stability and durability of the modified layer structure: This invention achieves metallurgical bonding between Zn nanoparticles and titanium alloy substrate through the solid-state stirring action of FSP, resulting in high bonding strength and avoiding the problem of easy peeling of traditional coatings; CPF treatment is carried out in a nitrogen atmosphere, forming a slight nitriding layer on the surface of the titanium alloy, improving the surface hardness and corrosion resistance of the material; the composite process further enhances the structural stability of the modified layer, ensuring that it maintains structural integrity and performance stability in the human physiological environment for a long time, and extending the service life of the implant.

[0025] The process is green and controllable, with potential for personalized customization: The FSP and CPF processes used in this invention do not require the use of toxic and harmful chemical reagents. FSP is carried out under argon protection, and CPF is carried out in a nitrogen atmosphere, with no pollutant emissions throughout the process. Moreover, the parameters of both processes can be precisely controlled, and the Zn ion content, grain size and surface roughness can be flexibly adjusted according to clinical needs to achieve personalized customization of modification effects and adapt to different orthopedic implantation scenarios. Attached Figure Description

[0026] Figure 1 for β Microscopic morphology images of titanium alloys, where a represents the microstructure of titanium alloy in Example 1. β Surface microstructure of titanium alloy substrate; b is the microstructure of titanium alloy substrate in Example 1. β Microstructure of titanium alloy after surface modification by friction stir; c is the microstructure of titanium alloy in Example 1. β Microstructure of titanium alloy after surface modification by compressed plasma flow; Figure 2 This is a gradient grain structure morphology diagram, where a represents the structure in Example 1. β The overall cross-sectional gradient grain structure morphology of the titanium alloy after friction stir processing; b is the morphology of Example 1. β The morphology of the ultrafine grain region in the titanium alloy cross-section; c represents the morphology in Example 1. β The morphology of the transition zone in the titanium alloy section; d represents the morphology in Example 1. β Morphology of the heat-affected zone in titanium alloy cross-sections; Figure 3 In the table, a is a fluorescence image of rat bone marrow mesenchymal stem cells on the substrate surface in Example 1; b is a fluorescence image of rat bone marrow mesenchymal stem cells on the surface of sample FSP-1 in Example 1; c is a fluorescence image of rat bone marrow mesenchymal stem cells on the surface of sample FSP-2 in Example 2; d is a fluorescence image of rat bone marrow mesenchymal stem cells on the surface of sample CPF-1 in Example 1; and e is a fluorescence image of rat bone marrow mesenchymal stem cells on the surface of sample CPF-2 in Example 2. Figure 4In the images, a is an image of alkaline phosphatase-induced osteogenic differentiation staining on the surface of the substrate in Example 1; b is an image of alkaline phosphatase-induced osteogenic differentiation staining on the surface of sample FSP-1 in Example 1; c is an image of alkaline phosphatase-induced osteogenic differentiation staining on the surface of sample FSP-2 in Example 2; d is an image of alkaline phosphatase-induced osteogenic differentiation staining on the surface of sample CPF-1 in Example 1; and e is an image of alkaline phosphatase-induced osteogenic differentiation staining on the surface of sample CPF-2 in Example 2. Detailed Implementation

[0027] Terminology Explanation: β Titanium alloy: specifically refers to Ti-35Nb-2Ta-3Zr (TNTZ) high-strength low-modulus titanium alloy. This alloy does not contain aluminum and vanadium elements with toxic side effects, and its mechanical properties are highly compatible with human bone tissue, making it one of the preferred base materials in the field of orthopedic implants.

[0028] Friction stirring (FSP): A solid-phase material processing technology that uses a high-speed rotating stirring head to generate heat through friction with the material and achieve solid stirring and plasticization. It uses thermomechanical action to refine the grain size, eliminate defects, or perform composite modification of the material. The material does not melt during the processing and can retain the original excellent properties of the base material to the greatest extent.

[0029] Compressed plasma flow (CPF): A type of intense pulsed cryogenic plasma generated by a magnetoplasm compressor in a near-steady-state plasma accelerator. It features high velocity, high energy density, and long discharge time, and can be used for precise modification of material surfaces.

[0030] Surface topology: refers to the microscopic geometric morphology formed on the surface of a material through modification treatment. Its roughness, pore distribution and other characteristics directly affect the adhesion and proliferation behavior of cells on the material surface.

[0031] Biocompatibility: When the material interacts with the human biological environment, it has good cell compatibility, tissue compatibility and mechanical compatibility, and will not cause adverse consequences such as immune rejection or toxic reactions, and can meet the clinical application requirements of orthopedic implants.

[0032] This invention provides a biocompatible β A method for composite modification of titanium alloy surfaces, characterized by comprising the following steps: Step (1), pre-treated medical βA continuous groove structure is machined onto the surface of a titanium alloy substrate, and bioactive particles are introduced. For example, a continuous groove structure is machined on the pretreated titanium alloy surface using a CNC milling machine. The grooves are 1 mm deep, 1 mm wide, and 2 mm apart, with the groove direction aligned with the subsequent FSP machining direction. These grooves are used to fill the bioactive particles. The bioactive particles are preferably Zn nanoparticles with a particle size of 50-100 nm, which are uniformly filled into the grooves at a density of 1.2 g / cm³. 3 After filling, use a scraper to smooth it out, ensuring that the Zn nanoparticles are flush with the surface of the trench.

[0033] Step (2): The substrate treated in step (1) is subjected to friction stirring to introduce bioactive particles into the surface layer of the substrate and construct a gradient grain structure. Specifically: Friction stir processing (FSP) Processing equipment and tools: A CNC friction stir machining machine tool is selected, equipped with a W-Re alloy stirring head (W content 95%, Re content 5%). The stirring head consists of a shoulder and a needle. Its process parameters are as follows: the shoulder diameter is 16mm, the needle is a truncated cone structure with a bottom diameter of 6mm, a top diameter of 4mm, and a needle length of 0.9mm (slightly smaller than the groove depth to ensure thorough stirring).

[0034] Processing parameters: The titanium alloy plate filled with Zn nanoparticles is fixed on a rigid worktable, and an argon protective atmosphere (argon flow rate of 15 L / min) is used to prevent oxidation of the material surface during processing. The processing parameters are as follows: the forward speed of the stirring head is preferably 50-100 mm / min, more preferably 50 mm / min; the rotation speed is preferably 150 r / min-300 r / min, more preferably 225 r / min-300 r / min; and the downward pressure is preferably 0.05-0.2 mm, more preferably 0.1 mm.

[0035] Processing procedure: The machine tool is started, and the stirring head rotates at high speed according to the set parameters while slowly pressing down. The friction between the shoulder and the material surface generates heat, causing the local material to heat up to a plastic state (approximately 700-800℃). The stirring needle is inserted into the groove and the surrounding material, and through shearing and stirring, the Zn nanoparticles are uniformly dispersed to the surface layer of the titanium alloy, while simultaneously refining the surface grains to form a gradient grain structure (the surface ultrafine grain size is 1-2μm, gradually increasing in size towards the interior). After processing, argon gas protection is maintained until the material cools to room temperature.

[0036] Step (3): The substrate treated in step (2) is subjected to compressed plasma flow treatment to uniformly distribute bioactive particles on the substrate surface and construct a topology with an average surface roughness of 3-6 μm suitable for cell growth. Specifically: Compressed Plasma Flow (CPF) Processing Processing Equipment and Environment: A compact magnetic plasma compressor (MPC) was used as the CPF generator. This device consists of a coaxial electrode system (the central electrode is the cathode, and six surrounding electrodes are the anodes), a capacitor energy storage device, and a vacuum system. The FSP-treated samples (samples FSP-1 and FSP-2) were fixed on the sample stage inside the vacuum chamber, ensuring that the processed surface was directly facing the plasma outlet. The entire experiment was conducted in a 400 Pa nitrogen atmosphere (nitrogen was used as the working gas and could also form a slight nitriding layer on the material surface, increasing surface hardness).

[0037] Processing parameters: The capacity of the capacitor energy storage device is preferably 1000-1500mF, more preferably 1200mF; the initial operating voltage is preferably 2-6 kV, more preferably 4kV; the plasma flow pulse duration is preferably 50-200 μs, more preferably 100 μs; the pulse interval is preferably 3-10 s, more preferably 5 s; a total of three pulse processes are performed; the plasma flow rate is preferably (4-8)×10 6 cm / s, more preferably (5-6)×10 6 The electron concentration is preferably (3-8) × 10 cm / s. 17 cm -3 More preferably, it is (4-7)×10 17 cm -3 The plasma temperature is 2-3 eV; the working distance between the sample and the plasma outlet is preferably 8-16 cm, more preferably 12 cm.

[0038] Processing procedure: After evacuating the vacuum system to the set pressure, nitrogen gas is introduced. The electrode spacing and working distance are adjusted, and the capacitor energy storage device is activated to discharge, generating a strong pulsed compressed plasma flow to etch and activate the FSP-treated surface. Through the physical impact and energy transfer of the plasma flow, the surface-agglomerated Zn nanoparticles are further dispersed, ensuring a uniform distribution of Zn ions on the surface layer. Simultaneously, a micron-level uneven structure is formed on the surface, ultimately obtaining a topological structure with an average surface roughness of 3-6 μm. After processing, the vacuum chamber is allowed to cool naturally to room temperature before the samples (sample CPF-1 and sample CPF-2) are removed.

[0039] In this invention, the preprocessing in step (1) is as follows: First, the medical-grade β-titanium alloy substrate is mechanically polished with sandpaper to remove surface oxide scale and impurities; then, it is ultrasonically cleaned with anhydrous ethanol to remove surface oil; finally, it is dried and ready for use. Specifically: Medical-grade β-titanium alloy Ti-35Nb-2Ta-3Zr (TNTZ) was selected as the base material. This alloy was processed into 5mm thick plates through vacuum melting, hot forging, and cold rolling. First, the surface of the titanium alloy plate was pretreated: it was mechanically polished sequentially with 180#, 400#, 800#, and 1200# sandpaper to remove surface oxide scale and impurities; then, it was ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove surface oil; finally, it was dried in a 60℃ vacuum drying oven for 2 hours for later use.

[0040] In summary, the present invention provides a method for surface modification of titanium alloys using a composite of FSP and CPF, achieving the following technical objectives: (1) Zn bioactive ions are stably introduced into the surface of TNTZ titanium alloy by FSP process, and a gradient grain structure is constructed to improve the surface mechanical properties and the number of bioactive sites. (2) The surface treated with FSP is modified by CPF technology to achieve uniform distribution of Zn ions and avoid agglomeration. (3) Precisely control the surface roughness of titanium alloy to form an average surface roughness of 3-6 μm, and construct a microscopic topological structure that is conducive to cell adhesion and proliferation; (4) The modified titanium alloy implant has mechanical compatibility that matches human bone tissue, excellent cell compatibility and efficient osteogenic properties, which accelerates the integration speed of the implant with bone tissue and improves the clinical application effect and the service life of the implant.

[0041] The technical solution and technical effects of the present invention will be described in detail below with reference to the accompanying drawings and specific experimental procedures.

[0042] Example 1 The β-titanium alloy surface modification technology involved in this embodiment includes three steps: material pretreatment, pretreatment before friction stir machining, surface modification treatment after friction stir machining, and surface modification treatment after compressed plasma flow. Step S1: Material Pretreatment Ti-35Nb-2Ta-3Zr (TNTZ) medical-grade β-titanium alloy was selected as the substrate. This alloy was processed into 5mm thick plates through vacuum melting, hot forging, and cold rolling. First, the surface of the titanium alloy plate underwent pretreatment: mechanical grinding with 180#, 400#, 800#, and 1200# sandpaper was performed sequentially to remove surface oxide scale and impurities; then, ultrasonic cleaning with anhydrous ethanol for 15 minutes was performed to remove surface oil; finally, it was dried in a 60℃ vacuum drying oven for 2 hours for later use. The grain morphology of the TNTZ medical-grade β-titanium alloy substrate after etching is shown below. Figure 1 As shown in (a).

[0043] Step S2: Pretreatment before Friction Stir Processing (FSP): A continuous groove structure is machined on the surface of the medical β-titanium alloy substrate pretreated in Step S1, and bioactive particles are introduced. For example, a continuous groove structure is machined on the pretreated titanium alloy surface using a CNC milling machine. The groove depth is 1 mm, the width is 1 mm, and the groove spacing is 2 mm. The groove direction is consistent with the subsequent FSP processing direction, and the grooves are used to fill the bioactive particles. The bioactive particles are preferably Zn nanoparticles with a particle size of 50-100 nm, which are uniformly filled into the grooves at a filling density of 1.2 g / cm³. 3 After filling, use a scraper to smooth it out, ensuring that the Zn nanoparticles are flush with the surface of the trench.

[0044] Step S3: Surface modification treatment for friction stir machining The substrate treated in step S2 is subjected to friction stirring to introduce bioactive particles into the surface layer of the substrate and construct a gradient grain structure. Specifically: Friction stir processing (FSP) Processing equipment and tools: A CNC friction stir machining machine tool is selected, equipped with a W-Re alloy stirring head (W content 95%, Re content 5%). The stirring head consists of a shoulder and a needle. Its process parameters are as follows: the shoulder diameter is 16mm, the needle is a truncated cone structure with a bottom diameter of 6mm, a top diameter of 4mm, and a needle length of 0.9mm (slightly smaller than the groove depth to ensure thorough stirring).

[0045] Processing parameters: The titanium alloy plate filled with Zn nanoparticles was fixed on a rigid worktable, and an argon protective atmosphere (argon flow rate of 15 L / min) was used to prevent oxidation of the material surface during processing. The processing parameters were: stirring head forward speed of 50 mm / min, rotation speed of 300 r / min, and downward pressure of 0.1 mm. The sample under these parameters was named FSP-1.

[0046] Processing procedure: The machine tool is started, and the stirring head rotates at high speed according to the set parameters while slowly pressing down. Friction between the shoulder and the material surface generates heat, raising the local material temperature to a plastic state (approximately 700-800℃). The stirring needle is inserted into the groove and surrounding material, and through shearing and stirring, Zn nanoparticles are uniformly dispersed to the surface layer of the titanium alloy, simultaneously refining the surface grains and forming a gradient grain structure (the surface ultrafine grain size is 1-2 μm, gradually increasing in size towards the interior). After processing, argon gas protection is maintained until the material cools to room temperature. The surface grain morphology of the titanium alloy after friction stirring processing is shown below. Figure 1 As shown in (b), the cross-sectional morphology is as follows: Figure 2 As shown.

[0047] Step S4: Surface modification treatment with compressed plasma flow The substrate treated in step S3 is subjected to compressed plasma flow treatment to uniformly distribute bioactive particles on the substrate surface and construct a topology with an average surface roughness of 3-6 μm suitable for cell growth. Specifically: Compressed Plasma Flow (CPF) Processing Processing Equipment and Environment: A compact magnetic plasma compressor (MPC) was used as the CPF generator. This device consists of a coaxial electrode system (the central electrode is the cathode, and six surrounding electrodes are the anodes), a capacitor energy storage device, and a vacuum system. The FSP-treated sample (sample FSP-1) was fixed on the sample stage inside the vacuum chamber, ensuring that the processed surface was directly facing the plasma outlet. The entire experiment was conducted in a 400 Pa nitrogen atmosphere (nitrogen was used as the working gas and could also form a slight nitriding layer on the material surface, increasing surface hardness).

[0048] Processing parameters: The capacitor energy storage device has a capacity of 1200 mF and an initial operating voltage of 4 kV; the plasma flow pulse duration is 100 μs, the pulse interval is approximately 5 s, and a total of three pulse processes are performed; the plasma flow velocity is 6 × 10⁻⁶. 6 cm / s, electron concentration is 5×10 17 cm-3; the working distance between the sample and the plasma outlet is 12 cm.

[0049] Processing procedure: After evacuating the vacuum system to the set pressure, nitrogen gas is introduced. The electrode spacing and working distance are adjusted, and the capacitor energy storage device is activated to discharge, generating a strong pulsed compressed plasma flow to etch and activate the FSP-treated surface. Through the physical impact and energy transfer of the plasma flow, the surface-agglomerated Zn nanoparticles are further dispersed, ensuring a uniform distribution of Zn ions on the surface layer. Simultaneously, a micron-level uneven structure is formed on the surface, ultimately obtaining a topological structure with an average surface roughness of 3-6 μm. After processing, the vacuum chamber is allowed to cool naturally to room temperature, and the sample is removed and named sample CPF-1. Figure 1 (c) shows the surface morphology of CPF-1.

[0050] Example 2: The difference between this embodiment and Embodiment 1 is that in step S3, the stirring head advance speed is 50 mm / min, the rotation speed is 225 r / min, and the downward pressure is 0.1 mm. This sample is named FSP-2. Subsequent compressed plasma flow surface modification is performed on the FSP-2 sample, and the resulting sample is named CPF-2. The other steps are the same as in Embodiment 1.

[0051] Example 3: The difference between this embodiment and Embodiment 1 is that, in step S3, the stirring head advance speed is 100 mm / min, the rotation speed is 300 r / min, and the downward pressure is 0.1 mm. This sample is named FSP-3. Subsequent compressed plasma flow surface modification is performed on the FSP-2 sample, and the resulting sample is named CPF-3. The other steps are the same as in Embodiment 1.

[0052] Example 4: The difference between this embodiment and Embodiment 1 is that in step S3, the stirring head advance speed is 100 mm / min, the rotation speed is 225 r / min, and the downward pressure is 0.1 mm. This sample is named FSP-4. Subsequent compressed plasma flow surface modification is performed on the FSP-2 sample, and the resulting sample is named CPF-4. Other steps are the same as in Embodiment 1.

[0053] Example 5: The difference between this embodiment and Embodiment 1 is that in step S3, the stirring head advance speed is 50 mm / min, the rotation speed is 150 r / min, and the downward pressure is 0.1 mm. This sample is named FSP-5. Subsequent compressed plasma flow surface modification is performed on the FSP-2 sample, and the resulting sample is named CPF-5. The other steps are the same as in Embodiment 1.

[0054] Example 6: The difference between this embodiment and Embodiment 1 is that, in step S3, the stirring head advance speed is 100 mm / min, the rotation speed is 150 r / min, and the downward pressure is 0.1 mm. This sample is named FSP-6. Subsequent compressed plasma flow surface modification is performed on the FSP-2 sample, and the resulting sample is named CPF-6. The other steps are the same as in Embodiment 1.

[0055] Example 7: The difference between this embodiment and Embodiment 1 is that in step S4, the duration of the plasma pulse of the compressed plasma flow is 50 μs, the working distance is 12 cm, and the obtained sample is named CPF-7. The other steps are the same as in Embodiment 1.

[0056] Example 8: The difference between this embodiment and Embodiment 1 is that in step S4, the duration of the plasma pulse of the compressed plasma flow is 50 μs, the working distance is 14 cm, and the obtained sample is named CPF-8. The other steps are the same as in Embodiment 1.

[0057] Example 9: The difference between this embodiment and Embodiment 1 is that in step S4, the duration of the plasma pulse of the compressed plasma flow is 100 μs, the working distance is 14 cm, and the obtained sample is named CPF-9. The other steps are the same as in Embodiment 1.

[0058] Example 10: The difference between this embodiment and Embodiment 1 is that in step S4, the duration of the plasma pulse of the compressed plasma flow is 200 μs, the working distance is 12 cm, and the obtained sample is named CPF-10. The other steps are the same as in Embodiment 1.

[0059] Example 11: The difference between this embodiment and Embodiment 1 is that, in step S4, the duration of the plasma pulse of the compressed plasma flow is 200 μs, the working distance is 14 cm, and the obtained sample is named CPF-11. The other steps are the same as in Embodiment 1.

[0060] Comparative Example 1: This comparative example only involves surface modification of the β-titanium alloy surface through friction stir processing.

[0061] Step S1: Material Pretreatment Medical-grade β-titanium alloy Ti-35Nb-2Ta-3Zr (TNTZ) was selected as the base material. This alloy was processed into 5mm thick plates through vacuum melting, hot forging, and cold rolling. First, the surface of the titanium alloy plate was pretreated: it was mechanically polished sequentially with 180#, 400#, 800#, and 1200# sandpaper to remove surface oxide scale and impurities; then, it was ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove surface oil; finally, it was dried in a 60℃ vacuum drying oven for 2 hours for later use.

[0062] Step S2: Pretreatment before Friction Stir Processing (FSP): A continuous groove structure is machined on the surface of the medical β-titanium alloy substrate pretreated in Step S1, and bioactive particles are introduced. For example, a continuous groove structure is machined on the pretreated titanium alloy surface using a CNC milling machine. The groove depth is 1 mm, the width is 1 mm, and the groove spacing is 2 mm. The groove direction is consistent with the subsequent FSP processing direction, and the grooves are used to fill the bioactive particles. The bioactive particles are preferably Zn nanoparticles with a particle size of 50-100 nm, which are uniformly filled into the grooves at a filling density of 1.2 g / cm³. 3 After filling, use a scraper to smooth it out, ensuring that the Zn nanoparticles are flush with the surface of the trench.

[0063] Step S3: Surface modification treatment for friction stir machining The substrate treated in step S2 is subjected to friction stirring to introduce bioactive particles into the surface layer of the substrate and construct a gradient grain structure. Specifically: Friction stir processing (FSP) Processing equipment and tools: A CNC friction stir machining machine tool is selected, equipped with a W-Re alloy stirring head (W content 95%, Re content 5%). The stirring head consists of a shoulder and a needle. Its process parameters are as follows: the shoulder diameter is 16mm, the needle is a truncated cone structure with a bottom diameter of 6mm, a top diameter of 4mm, and a needle length of 0.9mm (slightly smaller than the groove depth to ensure thorough stirring).

[0064] Processing parameters: The titanium alloy plate filled with Zn nanoparticles is fixed on a rigid worktable, and an argon protective atmosphere (argon flow rate of 15 L / min) is used to prevent oxidation of the material surface during processing. The processing parameters are: stirring head forward speed of 50 mm / min, rotation speed of 300 r / min, and downward pressure of 0.1 mm.

[0065] Processing procedure: The machine tool is started, and the stirring head rotates at high speed according to the set parameters while slowly pressing down. The friction between the shoulder and the material surface generates heat, causing the local material to heat up to a plastic state (approximately 700-800℃). The stirring needle is inserted into the groove and the surrounding material, and through shearing and stirring, the Zn nanoparticles are uniformly dispersed to the surface layer of the titanium alloy, while simultaneously refining the surface grains to form a gradient grain structure (the surface ultrafine grain size is 1-2μm, gradually increasing in size towards the interior). After processing, argon gas protection is maintained until the material cools to room temperature.

[0066] Comparative Example 2: The difference between this comparative example and Comparative Example 1 is that, in step S3, the rotation speed of the stirring head in the processing parameters is 225 r / min.

[0067] Comparative Example 3: Step S1: Material Pretreatment Medical-grade β-titanium alloy Ti-35Nb-2Ta-3Zr (TNTZ) was selected as the base material. This alloy was processed into 5mm thick plates through vacuum melting, hot forging, and cold rolling. First, the surface of the titanium alloy plate was pretreated: it was mechanically polished sequentially with 180#, 400#, 800#, and 1200# sandpaper to remove surface oxide scale and impurities; then, it was ultrasonically cleaned with anhydrous ethanol for 15 minutes to remove surface oil; finally, it was dried in a 60℃ vacuum drying oven for 2 hours for later use.

[0068] Step S2: Surface modification treatment with compressed plasma flow The substrate treated in step S1 is subjected to compressed plasma flow treatment to uniformly distribute bioactive particles on the substrate surface and construct a topology with an average surface roughness of 3-6 μm suitable for cell growth. Specifically: Compressed Plasma Flow (CPF) Processing Processing Equipment and Environment: A compact magnetic plasma compressor (MPC) was used as the CPF generator. This device consists of a coaxial electrode system (the central electrode is the cathode, and six surrounding electrodes are the anodes), a capacitor energy storage device, and a vacuum system. The substrate was fixed on the sample stage inside the vacuum chamber, ensuring that the processing surface was directly facing the plasma outlet. The entire experiment was conducted in a 400 Pa nitrogen atmosphere (nitrogen was used as the working gas and could also form a slight nitriding layer on the material surface, increasing surface hardness).

[0069] Processing parameters: The capacitor energy storage device has a capacity of 1200 mF and an initial operating voltage of 4 kV; the plasma flow pulse duration is 100 μs, the pulse interval is approximately 5 s, and a total of three pulse processes are performed; the plasma flow velocity is 6 × 10⁻⁶. 6 cm / s, electron concentration is 5×10 17 cm -3 The working distance between the sample and the plasma outlet is 12 cm.

[0070] Processing procedure: After evacuating the vacuum system to the set pressure, nitrogen gas is introduced. The electrode spacing and working distance are adjusted, and the capacitor energy storage device is activated to discharge, generating a strong pulsed compressed plasma flow to etch and activate the FSP-treated surface. Through the physical impact and energy transfer of the plasma flow, the surface-agglomerated Zn nanoparticles are further dispersed, ensuring a uniform distribution of Zn ions on the surface layer. Simultaneously, a micron-level uneven structure is formed on the surface, ultimately achieving a topological structure with an average surface roughness of 3-6 μm. After processing, the vacuum chamber is allowed to cool naturally to room temperature before the sample is removed.

[0071] The above embodiments and comparative examples were characterized, and the test methods and characterization results are as follows: (a) Microscopic morphological characterization The prepared material was etched and then placed under a scanning electron microscope (SEM) for microscopic morphology characterization, such as... Figure 1 As shown. The substrate has a relatively coarse grain size, with an average grain size of approximately 30 μm, such as... Figure 1 As shown in (a); after friction stirring, the grains are significantly refined due to deformation and recrystallization, with an average grain size of approximately 2 μm, as... Figure 1 As shown in (b), after surface treatment with compressed plasma flow, the material surface exhibits an uneven topological morphology with an average roughness of approximately 6 μm. Figure 1 As shown in (c), the cross-sectional morphology of the material after friction stirring is a gradient grain structure, as shown in [example]. Figure 2 As shown in (a), the gradient grain structure consists of an ultrafine grain region, a transition region, and a heat-affected region, as follows: Figure 2 As shown in (b), (c), and (d).

[0072] (b) Cell viability experiment The inoculation concentration on each sample surface was 2×10⁻⁶. 4 Rat bone marrow mesenchymal stem cells (rhMs) at a concentration of [number] cells / mL were cultured for one day in α-MEM complete medium, followed by a live / dead cell double staining experiment. Cell viability on the material surface was observed using a laser confocal microscope after staining. In the staining protocol, live cells were labeled green with Calcein-AM. It was observed that the substrate surface had the lowest number of live cells, such as [data missing]. Figure 3 As shown in (a), FSP-1 and FSP-2 have more live cells on their surfaces than on the substrate due to the release of Zn ions, such as... Figure 3 As shown in (b) and (c), CPF-1 and CPF-2, due to their higher surface roughness, facilitate cell adhesion, and combined with the effect of Zn ion release, result in more viable cells on their surface compared to FSP-1 and FSP-2. Figure 3 As shown in (d) and (e).

[0073] (c) Alkaline phosphatase staining experiment In a 24-well plate, with 2×10 4 Rat bone marrow mesenchymal stem cells were seeded onto the sample surface at a concentration of [cells / mL] and incubated for 7 days. Cells were fixed with 4% paraformaldehyde and washed three times with PBS buffer. Then, alkaline phosphatase staining was performed according to the instructions using an alkaline phosphatase staining kit. The staining results were observed and images were taken under a light microscope to assess the alkaline phosphatase expression level of the cells. It was observed that the alkaline phosphatase staining on the substrate surface was lighter, indicating a weaker osteogenic level. Figure 4 As shown in (a), due to the release of Zn ions, the alkaline phosphatase on the surface cells of FSP-1 and FSP-2 showed a deeper color than that on the substrate, indicating a higher level of osteogenic activity. Figure 4 As shown in (b) and (c), CPF-1 and CPF-2, due to their higher surface roughness, are more conducive to cell adhesion and proliferation. Combined with the effect of Zn ion release, the surface alkaline phosphatase staining is deeper than that of FSP-1 and FSP-2, indicating a better level of osteogenic activity. Figure 4 As shown in (d) and (e).

[0074] The above description is merely a preferred embodiment of the present invention. However, the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention should be covered within the scope of protection of the present invention.

Claims

1. A bioadapted β A method of surface composite modification of titanium alloys, characterized by The method comprises the following steps: Step (1), pre-treated medical β A continuous groove structure is machined on the surface of a titanium alloy substrate, and bioactive particles are introduced. Step (2), the substrate treated in step (1) is subjected to friction stir processing to introduce bioactive particles into the surface layer of the substrate and build a gradient grain structure; Step (3), the substrate treated in step (2) is subjected to compressed plasma flow processing to make the bioactive particles uniformly distributed on the surface of the substrate and build a topological structure with an average surface roughness of 3-6 μm suitable for cell growth.

2. A biocompatible according to claim 1 β Titanium alloy surface complex modification method, characterized by, In step (2), the friction stir processing parameters are as follows: The forward speed of the stirring head is 50-100 mm / min, the rotation speed is 150 r / min-300 r / min, and the pressing amount is 0.05-0.2 mm.

3. A biocompatible according to claim 1 β Titanium alloy surface complex modification method, characterized by, In step (2), the structure parameters of the stirring head in the friction stir processing are as follows: The shoulder diameter is 16 mm, the bottom diameter of the conical table-shaped needle part is 6 mm, the top diameter is 4 mm, and the length is 0.9 mm.

4. A biocompatible according to claim 1 β Titanium alloy surface complex modification method, characterized by, In step (3), the compressed plasma flow processing parameters are as follows: The capacity of the capacitor energy storage device is 1000-1500 mF, and the initial working voltage is 2-6 kV; the duration of the plasma flow pulse is 50-200 μs, the pulse interval is about 3-10 s, and a total of three pulse treatments are performed; the plasma flow rate is (4-8) × 10 6 cm / s, the electron concentration is (3-8) × 10 17 cm -3 ; and the working distance of the sample from the plasma flow outlet is 8-16 cm.

5. A biocompatible according to claim 1 β A method for surface composite modification of titanium alloys, characterized by In step (3), the compressed plasma flow processing is carried out under a nitrogen atmosphere of 400 Pa.

6. A biocompatible according to claim 1 β Titanium alloy surface complex modification method, characterized by, In step (2), the size of the ultra-fine grains in the surface layer of the gradient grain structure is 1-2 μm, which gradually increases towards the interior.

7. A biocompatible according to claim 1 β Titanium alloy surface complex modification method, characterized by, The bioactive particles are Zn nanoparticles.

8. A biocompatible one according to claim 7 β A method for composite modification of titanium alloy surfaces, characterized in that, The Zn nanoparticles have a particle size of 50-100 nm and a packing density of 1.2 g / cm 3 .

9. A biocompatible according to claim 1 β Titanium alloy surface complex modification method, characterized by, In the groove structure, the groove depth is 1 mm, the width is 1 mm, the groove spacing is 2 mm, and the groove direction is consistent with the friction stir processing direction.

10. A biocompatible according to any one of claims 1-9 β Titanium alloy surface complex modification method characterized by, In step (1), the pretreatment is: First, use sandpaper on the medical... β The titanium alloy substrate is mechanically polished to remove surface oxide scale and impurities; then ultrasonically cleaned with anhydrous ethanol to remove surface oil; finally dried for later use.

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