A novel high-toughness controllable degradation magnesium alloy bone nail and a preparation method thereof

Abstract

This invention belongs to the field of biomedical metal materials and devices, specifically disclosing a novel high-strength, tough, controllable degradable magnesium alloy bone nail and its preparation method. The method comprises: using Mg-30wt.%Sc alloy, Mg-10wt.%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99%wt.% as raw materials, and preparing Mg-Sc-Al-Mn alloy ingots under the protection of a mixed gas of CO2 and SF6; homogenizing the Mg-Sc-Al-Mn alloy ingots; then processing the Mg-Sc-Al-Mn alloy into bone nail blanks through reciprocating extrusion; processing the bone nail blanks into threaded Mg-Sc-Al-Mn alloy bone nails; and constructing a Mg(OH)F-(ScOF / Al3O3F3) composite passivation film layer on the surface of the threaded Mg-Sc-Al-Mn alloy bone nails. This invention uses NaF treatment to react with the Mg, Al, Mn, and Sc elements in the alloy of this invention, thereby constructing a novel Mg(OH)F-(ScOF / Al3O3F3) composite passivation film with strong bonding force in situ on the surface of the bone nail. Compared with the traditional MgF2 film, the synergistic effect of the three elements (Mg(OH)F, ScOF, and Al3O3F3) achieves a highly corrosion-resistant surface layer and internal densification enhancement, and realizes the self-repair of the passivation layer.

Description

Technical Field

[0001] This invention belongs to the field of biomedical metal materials and devices, and relates to a novel high-strength, tough, controllable degradable magnesium alloy bone nail and its preparation method. Background Technology

[0002] With the increasing aging of the population, the treatment of bone injuries faces severe challenges. Magnesium alloys, as revolutionary biomedical metallic materials, solve the rejection problem of traditional metal implants with their excellent biocompatibility; their unique in vivo biodegradability spares patients the pain of secondary surgery; more importantly, their elastic modulus of 40-45 GPa is highly matched with that of human bone, which can effectively eliminate the stress shielding effect caused by rigid implants and create an ideal mechanical environment for bone healing.

[0003] However, the widespread application of magnesium alloy bone screws still faces some key challenges, the core of which revolves around the fundamental contradiction of "uncontrollable degradation." Through alloying methods, such as employing "interphase potential regulation" strategies and optimizing the microstructure, it is possible to achieve a uniform and controllable degradation rate and a good balance between strength and toughness from the material itself.

[0004] In the alloying design of this invention, to avoid the formation of Mg, which commonly impairs plasticity and biocompatibility in Mg-Al alloys... 17 Al 12 This invention addresses the brittle phases and the Al-Mn phase with a high potential difference between the Al and the magnesium matrix in Mg-Al-Mn alloys. Guided by thermodynamic calculations, it adds Sc, Al, and Mn (in a mass ratio of approximately 9:6:5) to the Mg matrix to form a novel Al2(Sc, Mn) phase with a lower potential difference between the Al and the magnesium matrix, fundamentally reducing the tendency for galvanic corrosion. Furthermore, AlSc and Al3Mn nanophases precipitate during extrusion, improving strength and controllable degradation, and avoiding the formation of Mg phases that impair plasticity and biocompatibility. 17 Al 12 Brittle phase.

[0005] Besides alloying methods, large plastic deformation processes are effective means of controlling the microstructure of magnesium alloys. Reciprocating extrusion, as a highly efficient large plastic deformation technology, has the core advantage of achieving microstructural densification and refinement through the synergistic effect of back pressure and multi-pass extrusion. The conventional extrusion temperature for magnesium alloys is 350-450 ℃, and the extrusion-to-extrusion ratio is usually <10:1. The 280-300 ℃ used in this invention can reduce energy consumption while suppressing grain growth that may be induced by high temperatures, while the high true strain provides sufficient driving force for microstructural refinement and the induction of nano-precipitates.

[0006] Magnesium alloy bone screws suffer from rapid and uneven degradation in vivo, leading to premature failure of mechanical properties and the creation of a localized alkaline environment that hinders bone healing. Constructing a stable and dense protective layer on the screw surface can effectively address this issue. Fluorination has attracted attention due to its ability to form a chemically stable MgF2 layer with extremely low solubility in chloride-containing environments. However, current fluorination processes face several challenges. First, most studies currently use hydrofluoric acid, a highly polluting and corrosive treatment, which is environmentally unfriendly and requires strict operator protection, hindering large-scale implementation. Therefore, this invention employs NaF solution, which offers higher safety and environmental friendliness and is more suitable for large-scale industrial application. The concentration and treatment time of the NaF solution are specifically selected based on the four components: Mg, Sc, Al, and Mn. Second, the pure MgF2 conversion film is thin and may contain microcracks, and its protection relies primarily on physical isolation. The Mg(OH)F-(ScOF / Al3O3F3) composite passivation layer constructed in this invention has significant comprehensive advantages compared to traditional MgF2 films. This passivation layer is based on dense Mg(OH)F, with dense and chemically stable ScOF distributed on the surface of Mg(OH)F, while Al3O3F3 is uniformly dispersed on the surface and interior of Mg(OH)F. The highly stable and dense ScOF on the surface can directly resist the erosion of Cl⁻ ions in corrosive media. The uniformly distributed Al3O3F3 particles inside and on the surface can significantly improve the density and crack propagation resistance of the Mg(OH)F matrix. Traditional MgF2 films are prone to damage and localized corrosion during implantation, while Mg(OH)F, as the main passivation layer, can resist crack propagation through F⁻. - The passivation layer undergoes slow-release self-repair. In addition, traditional passivation films are prone to peeling off during implantation, while the Mg(OH)F-(ScOF / Al3O3F3) composite passivation layer is generated in situ on the surface of the alloy substrate, ensuring excellent bonding strength with the substrate, reducing the risk of peeling off during implantation, and ensuring the long-term stability and biocompatibility of the implanted device in the physiological environment.

[0007] Patent CN116121611A discloses a Mg-Zn-Sc-Al magnesium alloy with high corrosion resistance and high strength and toughness, and its preparation method, belonging to the field of magnesium alloy material preparation technology. This invention prepares the Mg-Zn-Sc-Al magnesium alloy through smelting, purification, controlling the type and amount of added elements, and modifying the heat treatment process, thereby improving the performance of existing magnesium alloys. However, this patent does not involve any surface treatment processes.

[0008] Patent CN116115833A discloses a biodegradable pure magnesium or magnesium alloy nail plate system for medical use, addressing issues such as crevice corrosion at the contact points of these nail plates. A polymer layer or thin film is introduced at the nail plate contact points to reduce solution retention, thereby minimizing crevice corrosion. Simultaneously, this polymer layer can carry biocompatible corrosion inhibitors for pure magnesium or magnesium alloys. During polymer degradation, the release of these inhibitors further suppresses degradation at the local nail plate sites. However, this system primarily relies on the polymer layer for localized protection and does not optimize the mechanical and corrosion resistance properties of the alloy.

[0009] In view of the above problems, this invention is proposed. Summary of the Invention

[0010] To overcome the above-mentioned shortcomings, the present invention provides a novel high-strength, tough, controllable degradable magnesium alloy bone nail and its preparation method.

[0011] The first objective of this invention is to provide a novel method for preparing a high-strength, tough, and controllable degradable magnesium alloy bone nail, comprising the following steps:

[0012] S1: Using Mg-30wt.%Sc alloy, Mg-10wt.%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99%wt.% as raw materials, Mg-Sc-Al-Mn alloy ingots are prepared under the protection of CO2 and SF6 mixed gas.

[0013] S2: Homogenize the Mg-Sc-Al-Mn alloy ingot;

[0014] S3: The homogenized Mg-Sc-Al-Mn alloy obtained in step S2 is processed into bone nail blanks by reciprocating extrusion.

[0015] S4: The bone nail blank obtained in step S3 is processed into a threaded Mg-Sc-Al-Mn alloy bone nail.

[0016] S5: Construct a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface of the threaded Mg-Sc-Al-Mn alloy bone nail obtained in step S4.

[0017] Preferably, the volume ratio of CO2 to SF6 in step S2 is 97:3.

[0018] Preferably, step S2 specifically involves: placing the Mg-Sc-Al-Mn alloy ingot into alumina powder and wrapping it with aluminum foil, and then holding it at a temperature of 360-400 ℃ for 16-30 h to perform homogenization treatment.

[0019] Preferably, step S3 specifically includes:

[0020] S31: Cut the homogenized Mg-Sc-Al-Mn alloy into cylinders with a diameter of Φ36 mm × 30 mm, and grind off the oxide film on the surface.

[0021] S32: Preheat the cylinder and the mold at 270-300 ℃ for 15-20 min. After the temperature reaches 280-300 ℃, perform 4-6 reciprocating extrusion processes, with an extrusion ratio of 6.1 for each pass.

[0022] S33: The reciprocating extruded alloy material is subjected to 260-300 ℃ and held for 10-20 min to obtain a reciprocating extruded annealed Mg-Sc-Al-Mn alloy billet;

[0023] S34: Extruding the reciprocating extrusion annealed Mg-Sc-Al-Mn alloy billet into Mg-Sc-Al-Mn alloy bone nail blanks with a diameter of 6 mm-10 mm.

[0024] Preferably, the threaded Mg-Sc-Al-Mn alloy bone nail in step S4 has a diameter of 4 mm-6 mm and a length of 10 mm-30 mm.

[0025] Preferably, step S5 specifically includes:

[0026] S51: The threaded Mg-Sc-Al-Mn alloy bone nail is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water.

[0027] S52: Immerse the bone nails treated in step S51 completely in a 0.005-0.03 mol / L NaF solution and treat them at 70-90 ℃ for 6-9 h;

[0028] S53: Take out the bone nail after step S52, rinse with deionized water, then dehydrate and dry with anhydrous ethanol to obtain a Mg-Sc-Al-Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface.

[0029] The second objective of this invention is to provide a novel high-strength, high-toughness, controllable degradable magnesium alloy bone nail prepared by the above method, the chemical composition of which, by mass percentage, is: Sc 0.75-1.25 wt.%, Al 0.5-1.0 wt.%, Mn 0.4-0.6 wt.%, with the balance being Mg.

[0030] Using the above technical solution, this invention forms an Al2(Sc, Mn) phase, which has not been reported in magnesium alloy systems, through the addition of Al, Mn, and Sc. This phase has a small potential difference with the magnesium matrix, reducing the susceptibility to galvanic corrosion from a thermodynamic perspective. This invention employs a low-temperature process of 280-300 °C combined with a five-pass (6.1 extrusion ratio per pass) high plastic deformation (reciprocating extrusion) process, which effectively refines the microstructure and induces the nano-precipitation of AlSc and Al3Mn phases, transforming the corrosion mode from pitting corrosion to uniform corrosion. Simultaneously, by reacting NaF solution with the Mg, Al, Mn, and Sc elements in the alloy of this invention, a Mg(OH)F-(ScOF / Al3O3F3) passivation film is generated in situ on the surface of the bone screw. This film has self-healing capabilities, effectively protecting the bone screw matrix and ensuring uniform and controllable degradation of the bone screw.

[0031] In this invention, an Al2(Sc, Mn) phase is formed in the alloy, along with the precipitation of AlSc and Al3Mn phases. The Al2(Sc, Mn) phase formed in this invention has a potential closer to that of the magnesium matrix, which thermodynamically reduces the tendency for galvanic corrosion. Simultaneously, the extrusion temperature of 280-300 °C, combined with five passes, refines the microstructure and induces the precipitation of AlSc and Al3Mn nanophases, enhancing the mechanical properties of the alloy. Furthermore, this invention uses only a low-concentration NaF solution (0.01 mol / L), avoiding the use of highly polluting and hazardous HF acid, thus reducing environmental pollution and making it more suitable for large-scale industrial application. On the other hand, the Mg(OH)F-(ScOF / Al3O3F3) passivation film generated in this invention is formed by the combined reaction of Mg, Al, Mn, and Sc elements in the alloy. Through the synergistic effect of ScOF, Al3O3F3 and Mg(OH)F, the surface layer achieves high corrosion resistance, internal densification and enhancement, and the passivation layer has self-healing function.

[0032] The beneficial effects of this invention are:

[0033] (1) The present invention forms a novel potential Al2(Sc,Mn) phase with a smaller potential than the magnesium matrix by alloying Sc, Mn and Al, thereby reducing the galvanic corrosion sensitivity.

[0034] (2) The low temperature of 280-300 ℃ combined with the large plastic deformation process adopted in this invention can effectively refine the microstructure and promote the precipitation of AlSc and Al3Mn nanophases, thereby synergistically improving the material strength and degradation uniformity.

[0035] (3) The present invention uses NaF treatment to react with the Mg, Al, Mn and Sc elements in the alloy of the present invention to construct a novel Mg(OH)F-(ScOF / Al3O3F3) passivation film with good bonding force with the bone nail in situ on the surface of the bone nail. Compared with the traditional MgF2 film layer, this passivation layer has high density and self-healing function, and more effectively protects the alloy substrate.

[0036] (4) The bone nail prepared by the present invention degrades uniformly and controllably. It degrades uniformly in 3.5 wt.% NaCl with a corrosion rate as low as 0.014 mm / y - 0.053 mm / y, thus achieving a synergistic improvement in the controllability of bone nail degradation and mechanical properties. Attached Figure Description

[0037] Figure 1 The image shows the microstructure of a reciprocatingly extruded Mg-Sc-Al-0.5Mn magnesium alloy.

[0038] Figure 2 TEM image of AlSc nanoprecipitates in a reciprocatingly extruded Mg-Sc-Al-0.5Mn magnesium alloy.

[0039] Figure 3 The image shows the XRD pattern of the reciprocating extruded Mg-Sc-Al-0.5Mn magnesium alloy.

[0040] Figure 4 This is a line distribution diagram of the Al2(Sc, Mn) phase and its surrounding elements.

[0041] Figure 5 This is a cross-sectional elemental distribution diagram of the passivation film constructed after NaF treatment.

[0042] Figure 6 XRD pattern of Mg-Sc-Al-0.5Mn magnesium alloy bone nail with passivation film.

[0043] Figure 7 SEM image of the constructed Mg(OH)F-(ScOF / Al3O3F3) passivation film.

[0044] Figure 8 This is a SEM image of the decorrosion product of a reciprocating extruded Mg-Sc-Al-0.5Mn magnesium alloy.

[0045] Figure 9 Image of a threaded Mg-Sc-Al-Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on its surface. Detailed Implementation

[0046] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0047] This invention provides the following technical solution:

[0048] A novel method for preparing a high-strength, tough, and controllable degradable magnesium alloy bone nail includes the following steps:

[0049] S1: Using Mg-30wt.%Sc alloy, Mg-10wt.%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99%wt.% as raw materials, Mg-Sc-Al-Mn alloy ingots are prepared under the protection of CO2 and SF6 mixed gas.

[0050] S2: Homogenize the Mg-Sc-Al-Mn alloy ingot;

[0051] S3: The homogenized Mg-Sc-Al-Mn alloy obtained in step S2 is processed into bone nail blanks by reciprocating extrusion.

[0052] S4: The bone nail blank obtained in step S3 is processed into a threaded Mg-Sc-Al-Mn alloy bone nail.

[0053] S5: Construct a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface of the threaded Mg-Sc-Al-Mn alloy bone nail obtained in step S4.

[0054] In some embodiments, the volume ratio of CO2 to SF6 in step S2 is 97:3.

[0055] In some embodiments, step S2 specifically involves: placing the Mg-Sc-Al-Mn alloy ingot into alumina powder and wrapping it with aluminum foil, and then homogenizing it by holding it at a temperature of 360-400 ℃ for 16-30 h.

[0056] In some embodiments, step S3 specifically includes:

[0057] S31: Cut the homogenized Mg-Sc-Al-Mn alloy into cylinders with a diameter of Φ36 mm × 30 mm, and grind off the oxide film on the surface.

[0058] S32: Preheat the cylinder and the mold at 270-300 ℃ for 15-20 min. After the temperature reaches 280-300 ℃, perform 4-6 reciprocating extrusion processes, with an extrusion ratio of 6.1 for each pass.

[0059] S33: The reciprocating extruded alloy material is subjected to 260-300 ℃ and held for 10-20 min to obtain a reciprocating extruded annealed Mg-Sc-Al-Mn alloy billet;

[0060] S34: Extruding the reciprocating extrusion annealed Mg-Sc-Al-Mn alloy billet into Mg-Sc-Al-Mn alloy bone nail blanks with a diameter of 6 mm-10 mm.

[0061] In some embodiments, the threaded Mg-Sc-Al-Mn alloy bone nail in step S4 has a diameter of 4 mm-6 mm and a length of 10 mm-30 mm.

[0062] In some embodiments, step S5 specifically includes:

[0063] S51: The threaded Mg-Sc-Al-Mn alloy bone nail is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water.

[0064] S52: Immerse the bone nails treated in step S51 completely in a 0.005-0.03 mol / L NaF solution and treat them at 70-90 ℃ for 6-9 h;

[0065] S53: Take out the bone nail after step S52, rinse with deionized water, then dehydrate and dry with anhydrous ethanol to obtain a Mg-Sc-Al-Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface.

[0066] The novel high-strength, high-toughness, controllable degradable magnesium alloy bone nail prepared by the above method has the following chemical composition by mass percentage: Sc 0.75-1.25 wt.%, Al 0.5-1.0 wt.%, Mn 0.4-0.6 wt.%, with the balance being Mg.

[0067] The raw materials used in the examples are magnesium and aluminum ingots with a purity of 99.99 wt.% or higher, Mg-30wt%Sc alloy and Mg-10wt%Mn alloy.

[0068] Example 1

[0069] The preparation of Mg-Sc-Al-0.5Mn alloy bone nails includes the following steps:

[0070] (1) Using Mg-30wt.%Sc alloy, Mg-10wt%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99% wt.% as raw materials, under the protection of CO2 and SF6 (gas volume ratio of 97:3), Mg-Sc-Al-0.5Mn alloy ingots were produced;

[0071] (2) The Mg-Sc-Al-0.5Mn alloy ingot was placed in alumina powder and wrapped with aluminum foil. It was then homogenized in a large box-type heat treatment furnace at a temperature of 380 °C for 24 h.

[0072] (3) Cut a Φ36 mm×30 mm cylinder from the homogenized Mg-Sc-Al-0.5Mn alloy using a wire EDM machine, and grind off the oxide film on the surface;

[0073] (4) Preheat the above cylinder and mold at 280 ℃ for 17 min. After the temperature reaches 280 ℃, perform 5 reciprocating extrusion processes, with an extrusion ratio of 6.1 for each pass.

[0074] (5) The extruded alloy material is subjected to 290 °C and held for 15 min to obtain a reciprocating extrusion annealed Mg-Sc-Al-0.5Mn alloy billet, and then immediately subjected to a single extrusion at this temperature to extrude Mg-Sc-Al-0.5Mn alloy rods with a diameter of 8 mm.

[0075] (6) The Mg-Sc-Al-0.5Mn alloy rod is precision machined into a threaded magnesium alloy bone nail with a diameter of 5 mm and a length of 25 mm.

[0076] (7) The Mg-Sc-Al-0.5Mn bone nails were ultrasonically cleaned in sequence with acetone, anhydrous ethanol and deionized water to remove surface oil stains;

[0077] (8) The Mg-Sc-Al-0.5Mn bone nail was completely immersed in a 0.01 mol / L NaF solution and treated in a reactor at 70 °C for 7 h.

[0078] (9) The bone nail was removed, rinsed with deionized water, then dehydrated and dried with anhydrous ethanol to obtain a Mg-Sc-Al-0.5Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface. The obtained Mg-Sc-Al-0.5Mn alloy sample had a yield strength of 350 MPa, a tensile strength of 400 MPa, and an elongation of 35%. The Mg-Sc-Al-0.5Mn bone nail degraded uniformly in 3.5 wt.% NaCl solution with a corrosion rate as low as 0.014 mm / y.

[0079] Example 2

[0080] The difference between this embodiment and Embodiment 1 is that the preparation of the Mg-0.75Sc-Al-0.5Mn alloy bone nail in this embodiment includes the following steps:

[0081] (1) Using Mg-30wt.%Sc alloy, Mg-10wt%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99% wt.% as raw materials, under the protection of CO2 and SF6 (gas volume ratio of 97:3), Mg-0.75Sc-Al-0.5Mn alloy ingots were produced;

[0082] (2) The Mg-0.75Sc-Al-0.5Mn alloy ingot was placed in alumina powder and wrapped with aluminum foil. It was then homogenized in a large box-type heat treatment furnace at a temperature of 380 °C for 24 h.

[0083] (3) Cut a Φ36 mm×30 mm cylinder from the homogenized Mg-0.75Sc-Al-0.5Mn alloy using a wire EDM machine, and grind off the oxide film on the surface;

[0084] (4) Preheat the above cylinder and mold at 300 °C for 17 min. After the temperature reaches 290 °C, perform 5 reciprocating extrusion processes, with an extrusion ratio of 6.1 for each pass.

[0085] (5) The extruded alloy material is subjected to 270 °C and held for 15 min to obtain a reciprocating extrusion annealed Mg-0.75Sc-Al-0.5Mn alloy billet, and then immediately subjected to a single extrusion at this temperature to extrude Mg-0.75Sc-Al-0.5Mn alloy rods with a diameter of 8 mm.

[0086] (6) The Mg-0.75Sc-Al-0.5Mn alloy rod is precision machined into a magnesium alloy bone nail with threads, a diameter of 5 mm and a length of 25 mm.

[0087] (7) The Mg-0.75Sc-Al-0.5Mn bone nails were ultrasonically cleaned in sequence with acetone, anhydrous ethanol and deionized water to remove surface oil stains;

[0088] (8) The Mg-0.75Sc-Al-0.5Mn bone nail was completely immersed in a 0.01 mol / L NaF solution and treated in a reactor at 80 °C for 9 h.

[0089] (9) The bone nail was removed, rinsed with deionized water, then dehydrated and dried with anhydrous ethanol to obtain a Mg-0.75Sc-Al-0.5Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface. The obtained Mg-0.75Sc-Al-0.5Mn alloy sample had a yield strength of 280 MPa, a tensile strength of 355 MPa, and an elongation of 31%. The Mg-0.75Sc-Al-0.5Mn bone nail degraded uniformly in 3.5 wt.% NaCl solution with a corrosion rate as low as 0.053 mm / y.

[0090] Example 3

[0091] The difference between this embodiment and Embodiment 1 is that the preparation of the Mg-1.25Sc-Al-0.5Mn alloy bone nail in this embodiment includes the following steps:

[0092] (1) Using Mg-30wt.%Sc alloy, Mg-10wt%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99% wt.% as raw materials, under the protection of CO2 and SF6 (gas volume ratio of 97:3), Mg-1.25Sc-Al-0.5Mn alloy ingots were produced;

[0093] (2) The Mg-1.25Sc-Al-0.5Mn alloy ingot was placed in alumina powder and wrapped with aluminum foil. It was then homogenized in a large box-type heat treatment furnace at a temperature of 380 °C for 24 h.

[0094] (3) Cut a Φ36 mm×30 mm cylinder from the homogenized Mg-1.25Sc-Al-0.5Mn alloy using a wire EDM machine, and grind off the oxide film on the surface;

[0095] (4) Preheat the above cylinder and mold at 300 °C for 17 min. After the temperature reaches 280 °C, perform 5 reciprocating extrusion processes, with an extrusion ratio of 6.1 for each pass.

[0096] (5) The extruded alloy material is subjected to 280 °C and held for 15 min to obtain a reciprocating extrusion annealed Mg-1.25Sc-Al-0.5Mn alloy billet, and then immediately subjected to a single extrusion at this temperature to extrude Mg-1.25Sc-Al-0.5Mn alloy rods with a diameter of 8 mm.

[0097] (6) The Mg-1.25Sc-Al-0.5Mn alloy rod is precision machined into a magnesium alloy bone nail with threads, a diameter of 5 mm and a length of 25 mm.

[0098] (7) The Mg-1.25Sc-Al-0.5Mn bone nails were ultrasonically cleaned in sequence with acetone, anhydrous ethanol and deionized water to remove surface oil stains;

[0099] (8) The Mg-1.25Sc-Al-0.5Mn bone nail was completely immersed in a 0.01 mol / L NaF solution and treated in a reactor at 80 °C for 8 h.

[0100] (9) The bone nail was removed, rinsed with deionized water, then dehydrated and dried with anhydrous ethanol to obtain a Mg-1.25Sc-Al-0.5Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface. The obtained Mg-1.25Sc-Al-0.5Mn alloy sample had a yield strength of 295 MPa, a tensile strength of 320 MPa, and an elongation of 28%. The Mg-1.25Sc-Al-0.5Mn bone nail degraded uniformly in 3.5 wt.% NaCl solution with a corrosion rate as low as 0.051 mm / y.

[0101] like Figure 1 The image shows the microstructure of the obtained Mg-Sc-Al-0.5Mn alloy after five reciprocating extrusion processes at 280 °C with an extrusion ratio of 6.1 per pass. The results show that after reciprocating extrusion, the alloy microstructure consists of micron-sized grains with good uniformity.

[0102] like Figure 2 The image shown is a TEM image of the nano-precipitated phases in the obtained Mg-Sc-Al-0.5Mn alloy bone nail material. The results show that after five reciprocating extrusion processes at 280 °C with an extrusion ratio of 6.1 per pass, uniform, fine and dispersed Al3Mn and AlSc nano-phases were precipitated in the alloy, which effectively improved the controllability of the alloy's degradation.

[0103] like Figure 3 The figure shows the XRD pattern of the reciprocating extruded Mg-Sc-Al-0.5Mn alloy. The results show that the Al2(Sc, Mn) phase is formed in the reciprocating extruded Mg-Sc-Al-0.5Mn alloy.

[0104] like Figure 4 The figure shows the elemental content distribution of the Al2(Sc, Mn) phase in the obtained reciprocating extrusion Mg-Sc-Al-0.5Mn alloy bone nail material. The results show that Sc, Al and Mn elements are significantly enriched in the Al2(Sc, Mn) phase.

[0105] like Figure 5The figure shows the cross-sectional elemental distribution of the passivation film constructed after NaF treatment. The results show that Mg, Sc, Al, O and F elements are enriched in the passivation film.

[0106] like Figure 6 The image shown is an XRD pattern of a Mg-Sc-Al-0.5Mn alloy bone nail with a passivation film. The results show that the passivation layer is Mg(OH)F-(ScOF / Al3O3F3).

[0107] like Figure 7 The image shown is a SEM image of the Mg(OH)F-(ScOF / Al3O3F3) passivation film constructed on the surface of the bone screw. The results show that the constructed Mg(OH)F-(ScOF / Al3O3F3) passivation film is relatively dense.

[0108] like Figure 8 The image shows the morphology of the de-corrosion products of the reciprocating extruded Mg-Sc-Al-0.5Mn alloy after corrosion in 3.5 wt.% NaCl solution. The results show that the corrosion behavior of the Mg-Sc-Al-0.5Mn alloy exhibits uniform degradation characteristics.

[0109] like Figure 9 The image shown is a diagram of a threaded Mg-Sc-Al-Mn alloy bone screw with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on its surface.

[0110] Example 4

[0111] In this embodiment, a Mg(OH)F-(ScOF / Al3O3F3) passivation film was prepared on the surface of a Mg-Sc-Al-0.5Mn bone screw using a 0.02 mol / L NaF solution, including the following steps:

[0112] (1) Using Mg-30wt.%Sc alloy, Mg-10wt%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99% wt.% as raw materials, under the protection of CO2 and SF6 (gas volume ratio of 97:3), Mg-Sc-Al-0.5Mn alloy ingots were produced;

[0113] (2) The Mg-Sc-Al-0.5Mn alloy ingot was placed in alumina powder and wrapped with aluminum foil. It was then homogenized in a large box-type heat treatment furnace at a temperature of 380 °C for 24 h.

[0114] (3) Cut a Φ36 mm×30 mm cylinder from the homogenized Mg-Sc-Al-0.5Mn alloy using a wire EDM machine, and grind off the oxide film on the surface;

[0115] (4) Preheat the above cylinder and mold at 300 °C for 17 min. After the temperature reaches 280 °C, perform 5 reciprocating extrusion processes, with an extrusion ratio of 6.1 for each pass.

[0116] (5) The extruded alloy material is subjected to 280 °C and held for 15 min to obtain a reciprocating extrusion annealed Mg-Sc-Al-0.5Mn alloy billet, and then immediately subjected to one extrusion at this temperature to extrude into Mg-Sc-Al-0.5Mn alloy rods with a diameter of 8 mm.

[0117] (6) The Mg-Sc-Al-0.5Mn alloy rod is precision machined into a threaded magnesium alloy bone nail with a diameter of 5 mm and a length of 25 mm.

[0118] (7) The Mg-Sc-Al-0.5Mn bone nails were ultrasonically cleaned in sequence with acetone, anhydrous ethanol and deionized water to remove surface oil stains;

[0119] (8) The Mg-Sc-Al-0.5Mn bone nail was completely immersed in a 0.02 mol / L NaF solution and treated in a reactor at 80 °C for 8 h.

[0120] (9) The bone nail was removed, rinsed with deionized water, then dehydrated and dried with anhydrous ethanol to obtain a Mg-Sc-Al-0.5Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface. The yield strength of the obtained Mg-Sc-Al-0.5Mn alloy sample was 343 MPa, the tensile strength was 394 MPa, and the elongation was 31%. The corrosion rate of the Mg-Sc-Al-0.5Mn bone nail in 3.5 wt.% NaCl solution was 0.039 mm / y.

[0121] Example 5

[0122] In this embodiment, a Mg(OH)F-(ScOF / Al3O3F3) passivation film was prepared on the surface of a Mg-Sc-Al-0.5Mn bone screw using a 0.005 mol / L NaF solution, including the following steps:

[0123] (1) Using Mg-30wt.%Sc alloy, Mg-10wt%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99% wt.% as raw materials, under the protection of CO2 and SF6 (gas volume ratio of 97:3), Mg-Sc-Al-0.5Mn alloy ingots were produced;

[0124] (2) The Mg-Sc-Al-0.5Mn alloy ingot was placed in alumina powder and wrapped with aluminum foil. It was then homogenized in a large box-type heat treatment furnace at a temperature of 380 °C for 24 h.

[0125] (3) Cut a Φ36 mm×30 mm cylinder from the homogenized Mg-Sc-Al-0.5Mn alloy using a wire EDM machine, and grind off the oxide film on the surface;

[0126] (4) Preheat the above cylinder and mold at 300 °C for 17 min. After the temperature reaches 280 °C, perform 5 reciprocating extrusion processes, with an extrusion ratio of 6.1 for each pass.

[0127] (5) The extruded alloy material is subjected to 280 °C and held for 15 min to obtain a reciprocating extrusion annealed Mg-Sc-Al-0.5Mn alloy billet, and then immediately subjected to a single extrusion at this temperature to extrude Mg-Sc-Al-0.5Mn alloy rods with a diameter of 8 mm.

[0128] (6) The Mg-Sc-Al-0.5Mn alloy rod is precision machined into a threaded magnesium alloy bone nail with a diameter of 5 mm and a length of 25 mm.

[0129] (7) The Mg-Sc-Al-0.5Mn bone nails were ultrasonically cleaned in sequence with acetone, anhydrous ethanol and deionized water to remove surface oil stains;

[0130] (8) The Mg-Sc-Al-0.5Mn bone nail was completely immersed in a 0.005 mol / L NaF solution and treated in a reactor at 80 °C for 8 h.

[0131] (9) The bone nail was removed, rinsed with deionized water, then dehydrated and dried with anhydrous ethanol to obtain a Mg-Sc-Al-0.5Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface. The yield strength of the obtained Mg-Sc-Al-0.5Mn alloy sample was 347 MPa, the tensile strength was 390 MPa, and the elongation was 33%. The corrosion rate of the Mg-Sc-Al-0.5Mn bone nail in 3.5 wt.% NaCl solution was 0.044 mm / y.

[0132] Example 6

[0133] In this embodiment, a reciprocating extrusion state Mg-Sc-Al-0.5Mn bone nail is prepared by two-pass reciprocating extrusion with an extrusion ratio of 6.1 per pass, including the following steps:

[0134] (1) Using Mg-30wt.%Sc alloy, Mg-10wt%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99% wt.% as raw materials, under the protection of CO2 and SF6 (gas volume ratio of 97:3), Mg-Sc-Al-0.5Mn alloy ingots were produced;

[0135] (2) The Mg-Sc-Al-0.5Mn alloy ingot was placed in alumina powder and wrapped with aluminum foil. It was then homogenized in a large box-type heat treatment furnace at a temperature of 380 °C for 24 h.

[0136] (3) Cut a Φ36 mm×30 mm cylinder from the homogenized Mg-Sc-Al-0.5Mn alloy using a wire EDM machine, and grind off the oxide film on the surface;

[0137] (4) Preheat the above cylinder and mold at 280 °C for 17 min. After the temperature reaches 280 °C, perform two reciprocating extrusion processes with an extrusion ratio of 6.1 for each pass.

[0138] (5) The extruded alloy material is subjected to 290 °C and held for 15 min to obtain a reciprocating extrusion annealed Mg-Sc-Al-0.5Mn alloy billet, and then immediately subjected to a single extrusion at this temperature to extrude Mg-Sc-Al-0.5Mn alloy rods with a diameter of 8 mm.

[0139] (6) The Mg-Sc-Al-0.5Mn alloy rod is precision machined into a threaded magnesium alloy bone nail with a diameter of 5 mm and a length of 25 mm.

[0140] (7) The Mg-Sc-Al-0.5Mn bone nails were ultrasonically cleaned in sequence with acetone, anhydrous ethanol and deionized water to remove surface oil stains;

[0141] (8) The Mg-Sc-Al-0.5Mn bone nail was completely immersed in a 0.01 mol / L NaF solution and treated in a reactor at 70 °C for 7 h.

[0142] (9) The bone nail was removed, rinsed with deionized water, then dehydrated and dried with anhydrous ethanol to obtain a Mg-Sc-Al-0.5Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface. The yield strength of the obtained Mg-Sc-Al-0.5Mn alloy sample was 323 MPa, the tensile strength was 378 MPa, and the elongation was 26%. The corrosion rate of the Mg-Sc-Al-0.5Mn bone nail in 3.5 wt.% NaCl solution was 0.056 mm / y.

[0143] Example 7

[0144] In this embodiment, a reciprocating extrusion state Mg-Sc-Al-0.5Mn bone nail is prepared by five reciprocating extrusion passes with an extrusion ratio of 3.3 per pass, including the following steps:

[0145] (1) Using Mg-30wt.%Sc alloy, Mg-10wt%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99% wt.% as raw materials, under the protection of CO2 and SF6 (gas volume ratio of 97:3), Mg-Sc-Al-0.5Mn alloy ingots were produced;

[0146] (2) The Mg-Sc-Al-0.5Mn alloy ingot was placed in alumina powder and wrapped with aluminum foil. It was then homogenized in a large box-type heat treatment furnace at a temperature of 380 °C for 24 h.

[0147] (3) Cut a Φ36 mm×30 mm cylinder from the homogenized Mg-Sc-Al-0.5Mn alloy using a wire EDM machine, and grind off the oxide film on the surface;

[0148] (4) Preheat the above cylinder and mold at 280 °C for 17 min. After the temperature reaches 280 °C, perform 5 reciprocating extrusion processes, with an extrusion ratio of 3.3 for each pass.

[0149] (5) The extruded alloy material is subjected to 290 °C and held for 15 min to obtain a reciprocating extrusion annealed Mg-Sc-Al-0.5Mn alloy billet, and then immediately subjected to a single extrusion at this temperature to extrude Mg-Sc-Al-0.5Mn alloy rods with a diameter of 8 mm.

[0150] (6) The Mg-Sc-Al-0.5Mn alloy rod is precision machined into a threaded magnesium alloy bone nail with a diameter of 5 mm and a length of 25 mm.

[0151] (7) The Mg-Sc-Al-0.5Mn bone nails were ultrasonically cleaned in sequence with acetone, anhydrous ethanol and deionized water to remove surface oil stains;

[0152] (8) The Mg-Sc-Al-0.5Mn bone nail was completely immersed in a 0.01 mol / L NaF solution and treated in a reactor at 70 °C for 7 h.

[0153] (9) The bone nail was removed, rinsed with deionized water, then dehydrated and dried with anhydrous ethanol to obtain a Mg-Sc-Al-0.5Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface. The yield strength of the obtained Mg-Sc-Al-0.5Mn alloy sample was 331 MPa, the tensile strength was 387 MPa, and the elongation was 24%. The corrosion rate of the Mg-Sc-Al-0.5Mn bone nail in 3.5 wt.% NaCl solution was 0.037 mm / y.

[0154] Experimental Example 1

[0155] Adjust the NaF concentration according to Table 1, and follow the same procedure as in Example 1.

[0156] Table 1

[0157] NaF concentration (mol / L) Comparative Example 1 0.001 Comparative Example 2 0.005 Comparative Example 3 0.01 Comparative Example 4 0.02 Comparative Example 5 0.03 Comparative Example 6 0.04 Comparative Example 7 0.05

[0158] The test results are detailed in Table 2.

[0159] Table 2

[0160] Yield strength (MPa) Tensile strength (MPa) Elongation (%) Corrosion rate (mm / y) Comparative Example 1 342 378 30 0.092 Comparative Example 2 347 390 33 0.044 Comparative Example 3 350 400 35 0.014 Comparative Example 4 343 394 31 0.039 Comparative Example 5 339 386 29 0.047 Comparative Example 6 341 391 33 0.052 Comparative Example 7 336 388 27 0.059

[0161] Referring to Table 2, the prepared product exhibits good performance within the NaF concentration range of 0.005-0.03 mol / L, with the best results observed at a concentration of 0.01 mol / L.

[0162] Experimental Example 2

[0163] Experimental groups: Comparative Example 8 and Example 1. The difference between Comparative Example 8 and Example 1 is that NaF was replaced with HF.

[0164] Experimental results: The yield strength of the obtained Mg-Sc-Al-0.5Mn alloy sample was 321 MPa, the tensile strength was 382 MPa, and the elongation was 30%. The corrosion rate of the Mg-Sc-Al-0.5Mn bone nail in 3.5 wt.% NaCl solution was 0.11 mm / y.

[0165] By comparing the performance of the products obtained in Example 1 and Comparative Example 8, it can be seen that the performance of the products obtained in Comparative Example 8 is lower than that of Example 1, further proving that the use of NaF can effectively improve product performance.

[0166] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0167] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a novel high-strength, tough, controllable degradable magnesium alloy bone nail, characterized in that, Includes the following steps: S1: Using Mg-30wt.%Sc alloy, Mg-10wt.%Mn alloy, high-purity Al and high-purity Mg with a purity ≥99.99%wt.% as raw materials, Mg-Sc-Al-Mn alloy ingots are prepared under the protection of CO2 and SF6 mixed gas. S2: Homogenize the Mg-Sc-Al-Mn alloy ingot; S3: The homogenized Mg-Sc-Al-Mn alloy obtained in step S2 is processed into bone nail blanks by reciprocating extrusion. S4: The bone nail blank obtained in step S3 is processed into a threaded Mg-Sc-Al-Mn alloy bone nail. S5: Construct a Mg(OH)F-(ScOF / Al3O3F3) composite passivation film on the surface of the threaded Mg-Sc-Al-Mn alloy bone nail obtained in step S4.

2. The method for preparing a novel high-strength, tough, controllable degradable magnesium alloy bone nail as described in claim 1, characterized in that, The volume ratio of CO2 to SF6 in step S1 is 97:

3.

3. The method for preparing a novel high-strength, tough, controllable degradable magnesium alloy bone nail as described in claim 1, characterized in that, Step S2 specifically involves placing the Mg-Sc-Al-Mn alloy ingot into alumina powder and wrapping it with aluminum foil, then holding it at 360-400 ℃ for 16-30 h to homogenize it.

4. The method for preparing a novel high-strength, tough, controllable degradable magnesium alloy bone nail as described in claim 1, characterized in that, Step S3 is as follows: S31: Cut the homogenized Mg-Sc-Al-Mn alloy into cylinders with a diameter of Φ36 mm × 30 mm, and grind off the oxide film on the surface. S32: Preheat the cylinder and the mold at 270-300 ℃ for 15-20 min. After the temperature reaches 280-300 ℃, perform 4-6 reciprocating extrusion processes, with an extrusion ratio of 6.1 for each pass. S33: The reciprocating extruded alloy material is subjected to 260-300 ℃ and held for 10-20 min to obtain a reciprocating extruded annealed Mg-Sc-Al-Mn alloy billet; S34: Extruding the reciprocating extrusion annealed Mg-Sc-Al-Mn alloy billet into Mg-Sc-Al-Mn alloy bone nail blanks with a diameter of 6 mm-10 mm.

5. The method for preparing a novel high-strength, tough, controllable degradable magnesium alloy bone nail as described in claim 1, characterized in that, The threaded Mg-Sc-Al-Mn alloy bone nails in step S4 have a diameter of 4 mm-6 mm and a length of 10 mm-30 mm.

6. The method for preparing a novel high-strength, tough, controllable degradable magnesium alloy bone nail as described in claim 1, characterized in that, Step S5 is as follows: S51: The threaded Mg-Sc-Al-Mn alloy bone nail is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water. S52: Immerse the bone nails treated in step S51 completely in a 0.005-0.03 mol / L NaF solution and treat them at 70-90 ℃ for 6-9 h; S53: Take out the bone nail after step S52, rinse with deionized water, then dehydrate and dry with anhydrous ethanol to obtain a Mg-Sc-Al-Mn alloy bone nail with a Mg(OH)F-(ScOF / Al3O3F3) passivation film on the surface.

7. A novel high-strength, tough, controllable degradable magnesium alloy bone nail prepared by the method described in any one of claims 1-6, characterized in that, Its chemical composition by mass percentage is: Sc 0.75-1.25 wt.%, Al 0.5-1.0 wt.%, Mn 0.4-0.6 wt.%, with the balance being Mg.

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