A high-strength corrosion-resistant magnesium alloy for orthopedic implant and a preparation method thereof

Abstract

This invention relates to the field of magnesium alloy technology, and discloses a high-strength, corrosion-resistant magnesium alloy for orthopedic implants and its preparation method. The alloy, by mass percentage, comprises: Gd 7.8%–9.5%, Y 2.5%–3.6%, Zn 1.2%–2.5%, Zr 0.25%–0.50%, with the balance being Mg and unavoidable impurity elements. Among the impurity elements, Fe≤0.02%, Cu≤0.02%, Ni≤0.02%, and Si≤0.03%, and the total mass percentage of impurity elements is ≤0.3%. The magnesium alloy has a multiphase structure, with an α-Mg solid solution matrix, which forms nanoscale precipitates after T6 heat treatment, with an average grain size ≤20μm. The magnesium alloy of this invention has a tensile strength ≥420MPa, a yield strength ≥300MPa, and an elongation ≥8%, meeting the mechanical requirements of load-bearing bone implants.

Description

Technical Field

[0001] This invention relates to the field of magnesium alloy technology, and more specifically, to a high-strength, corrosion-resistant magnesium alloy for orthopedic implants and its preparation method. Background Technology

[0002] Magnesium alloys, with their density close to that of natural human bone, excellent biocompatibility, and complete biodegradability, have become a core research direction for biodegradable implant materials in orthopedics, eliminating the need for secondary surgery. They have extremely high clinical application value in the field of load-bearing orthopedic implants such as bone nails, bone plates, and intramedullary nails.

[0003] Currently, medical magnesium alloys commonly used in clinical practice and research are mainly divided into two categories: The first category is commercially available ordinary magnesium alloys, such as AZ91, AZ31, and AZ91D. These alloys have mature manufacturing processes and low costs, but they have core defects such as insufficient strength and poor corrosion resistance. They are prone to pitting corrosion and rapid local degradation in vivo, which not only fails to meet the mechanical support requirements of load-bearing parts such as long bones of the limbs and spine, but also easily causes adverse reactions such as local hydrogen accumulation and tissue inflammation due to excessively rapid degradation. In addition, the Al element contained in the alloy has potential biosafety controversies, which limits its long-term application in the field of medical implants.

[0004] The second category is high-strength rare earth magnesium alloys, such as the Mg-Gd-Y-Zr series and WE43 alloy. These alloys achieve strength improvement through the addition of rare earth elements, but still have obvious shortcomings: the raw material cost is high, making it difficult to carry out large-scale clinical applications; the degradation behavior is uncontrollable, the corrosion rate does not match the bone healing cycle, and it is easy to have problems such as premature degradation failure or slow degradation; at the same time, its microstructure is difficult to control, and it is difficult to balance corrosion resistance and toughness, and it cannot simultaneously meet the multiple stringent requirements of orthopedic implants for mechanical properties, corrosion resistance and biosafety.

[0005] In summary, existing medical magnesium alloys generally cannot simultaneously achieve a synergistic balance of high strength, high corrosion resistance, controllable degradation rate, excellent biocompatibility, and low cost, making them unsuitable for the clinical use of load-bearing orthopedic implants. Therefore, developing a novel medical magnesium alloy with safe composition, satisfactory mechanical properties, excellent corrosion resistance, a degradation rate that matches bone healing, and controllable cost has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention provides a high-strength corrosion-resistant magnesium alloy for orthopedic implants and a method for preparing the same, aiming to solve the above-mentioned problems.

[0007] On one hand, the present invention provides a high-strength, corrosion-resistant magnesium alloy for orthopedic implants. The chemical composition of the magnesium alloy, by mass percentage, includes: Gd 7.8%-9.5%, Y 2.5%-3.6%, Zn 1.2%-2.5%, Zr 0.25%-0.50%, with the balance being Mg and unavoidable impurity elements; among the impurity elements, Fe≤0.02%, Cu≤0.02%, Ni≤0.02%, Si≤0.03%, and the total mass percentage of impurity elements ≤0.3%. The magnesium alloy has a multiphase structure with an α-Mg solid solution matrix. After T6 heat treatment, nanoscale precipitates are formed with an average grain size ≤20μm.

[0008] Preferably, the chemical composition of the magnesium alloy, by mass percentage, includes: 8.5% Gd, 3.0% Y, 1.8% Zn, 0.35% Zr, with the balance being Mg and unavoidable impurity elements.

[0009] On the other hand, the present invention also provides a method for preparing a high-strength, corrosion-resistant magnesium alloy for orthopedic implants, comprising the following steps: S1. Raw material pretreatment: Preheat pure magnesium ingots, Mg-Gd master alloy, Mg-Y master alloy, pure zinc ingots, and Mg-Zr master alloy to 150℃-200℃ to remove surface moisture from the raw materials. S2. Melting: Under the protective atmosphere of a mixed gas of CO2 and SF6, at 700℃-750℃, pretreated pure magnesium ingots, Mg-Gd master alloy, Mg-Y master alloy, pure zinc ingots and Mg-Zr master alloy are added in sequence, stirred evenly and kept at the temperature. S3. Refining and settling: At 740℃-760℃, add KCl-CaCl2-BaCl2-CaF2-YCl3 refining agent to the melt after smelting, stir for 15-25 minutes, and then let stand for 30-40 minutes to complete the purification of the melt. S4. Casting: Remove the slag from the surface of the melt and pour the melt into a metal mold preheated to 180℃-220℃ at 690℃-710℃ to obtain an ingot. S5. Solution treatment: The ingot is solution treated at 510℃-525℃ for 8-12 hours, and then quenched in 80℃ hot water. S6. Aging treatment: The quenched ingot is aged at 200℃-205℃ for 55-65 hours, and then air-cooled to obtain magnesium alloy.

[0010] Preferably, in step S1, the Mg-Gd master alloy is a Mg-30Gd master alloy, the Mg-Y master alloy is a Mg-30Y master alloy, and the Mg-Zr master alloy is a Mg-30Zr master alloy.

[0011] Preferably, in step S5, the solution treatment temperature is 515℃-520℃, and the treatment time is 8-10 hours.

[0012] Preferably, in step S6, the aging treatment temperature is 200℃-205℃, and the treatment time is 55-60 hours.

[0013] Furthermore, this invention also protects the application of a high-strength, corrosion-resistant magnesium alloy for orthopedic implants in the preparation of orthopedic implants.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention, through precise alloy composition and synergistic control of the T6 heat treatment process, enables magnesium alloys to stably achieve performance indicators of tensile strength ≥420MPa, yield strength ≥300MPa, and elongation ≥8%. Compared with existing commercial AZ91D and WE43 magnesium alloys, both tensile strength and yield strength are improved, while also taking into account good plasticity and toughness. It solves the core problem of insufficient strength of existing medical magnesium alloys and their inability to adapt to the implantation needs of load-bearing parts such as long bones of the limbs and spine. It can maintain stable mechanical support throughout the bone healing cycle and avoid fixation failure caused by implant deformation and breakage.

[0015] The magnesium alloy of this invention exhibits excellent corrosion resistance, with a neutral salt spray corrosion rate ≤0.40 mg / cm² / day and an acidic salt spray corrosion rate ≤0.75 mg / cm² / day. It degrades uniformly throughout in simulated human body fluid environments, without localized pitting, intergranular corrosion, or other abnormal corrosion behaviors. Compared to existing commercially available magnesium alloys prone to localized degradation, this invention reduces the formation of corrosion micro-cells through multi-element synergistic regulation, avoiding premature perforation and breakage of implants caused by rapid localized degradation. Simultaneously, it eliminates adverse reactions such as inflammation and edema in surrounding tissues caused by excessive localized release of metal ions, thus improving the in vivo service stability of the implant.

[0016] This invention employs an Al-free safe component system, avoiding potential biosafety risks such as neurotoxicity and bone metabolism inhibition caused by long-term accumulation of Al in the body. The Gd, Y, Zn, and Zr elements added to the alloy are all rare earth elements or trace essential elements for the human body with good biocompatibility. They are non-cytotoxic, non-sensitizing, and non-immunogenic, fully meeting the biosafety evaluation standards for orthopedic implant materials. This can effectively reduce the risk of foreign body reaction and immune rejection after implantation and is compatible with the physiological process of bone healing in the human body.

[0017] During the in vivo degradation process, the magnesium alloy of this invention forms a dense, uniform, and strongly bonded composite corrosion product film. This film can block corrosive media, effectively delaying and steadily controlling the degradation rate, thus solving the problems of excessively fast / slow degradation and uncontrollable degradation rates in existing medical magnesium alloys. Its degradation rate matches the physiological healing cycle of human weight-bearing bones, maintaining over 80% of residual mechanical strength during the critical bone healing period of 3-6 months post-surgery, ensuring stable fixation of the fracture site. After complete bone healing, it can gradually and completely degrade in vivo without the need for secondary surgery, reducing surgical trauma, treatment time, and economic burden for patients. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 These are metallographic microstructure images at different scales provided in Embodiment 1 of the present invention; Figure 2 This is a dispersion distribution diagram of the precipitated phase provided in Embodiment 5 of the present invention; Figure 3 Metallographic micrographs at different magnifications provided in Embodiment 5 of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Example 1

[0023] Alloy chemical composition (mass percentage): Gd 8.5%, Y 3.0%, Zn 1.8%, Zr 0.35%, balance Mg; unavoidable impurity elements: Fe 0.012%, Cu 0.008%, Ni 0.003%, Si 0.018%, total impurity content 0.041%.

[0024] The experimental raw materials were medical-grade pure magnesium ingots (purity ≥99.95%), Mg-30Gd master alloy, Mg-30Y master alloy, pure zinc ingots (purity ≥99.99%), and Mg-30Zr master alloy; the refining agent was the KCl-CaCl2-BaCl2-CaF2-YCl3 system.

[0025] Preparation process: (1) Raw material pretreatment: Place all the above raw materials in a forced-air drying oven, preheat to 180℃ and keep warm for 2 hours to thoroughly remove the moisture and oil adsorbed on the surface of the raw materials; (2) Smelting: Under the protection of a CO2+SF6 mixed gas with a volume ratio of 99:1 throughout the process, the resistance furnace is heated to 720℃. First, pure magnesium ingots are added until completely melted. Then, Mg-30Gd and Mg-30Y master alloys are added in sequence and stirred for 10 minutes until completely melted. Then, pure zinc ingots and Mg-30Zr master alloys are added and stirred continuously for 15 minutes until the composition is uniform. The mixture is then kept at the temperature for 20 minutes. (3) Refining and settling: Raise the furnace temperature to 750°C, add 2% of the total mass of the melt as a refining agent, stir continuously for 20 minutes to complete the refining, and then keep it at the temperature for 35 minutes to allow the inclusions and harmful impurities in the melt to settle fully and remove the surface slag. (4) Casting: Reduce the furnace temperature to 700°C, pour the melt into a steel metal mold that has been preheated to 200°C, and air cool it to room temperature to obtain an alloy ingot; (5) Solution treatment: Place the ingot in a box-type heat treatment furnace and keep it at 520℃ for 10 hours. After taking it out, quickly transfer it to 80℃ hot water for quenching. The total transfer time is ≤5s. (6) Aging treatment: The quenched ingot is placed back into the box-type heat treatment furnace and held at 205℃ for 60 hours. After removal, it is air-cooled to room temperature to obtain the target magnesium alloy sample, such as Figure 1 As shown.

[0026] Microstructure characterization shows that the alloy matrix is ​​an α-Mg solid solution (HCP structure). After T6 heat treatment, a uniformly dispersed nanoscale β' precipitate is formed, with no coarse second phase and an average grain size of 12 μm, which meets the technical requirement of ≤20 μm.

[0027] Performance test results

[0028] (1) Mechanical properties at room temperature: According to GB / T228.1-2021 "Metallic materials, tensile testing - Part 1: Test method at room temperature", the gauge length of the specimen is 50 mm, the tensile rate is 1 mm / min, and the tensile strength is 430 MPa, the yield strength is 310 MPa, and the elongation after fracture is 8.5%; (2) Corrosion resistance: The neutral salt spray test was conducted according to GB / T10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test". The test conditions were: 5% NaCl aqueous solution, temperature 35℃, pH value 6.5-7.2, continuous spraying for 72h. The neutral salt spray corrosion rate was measured to be 0.35mg / cm² / day. (3) In vitro degradation performance: After immersion in simulated body fluid (SBF) at 37℃ and pH 7.4 for 30 days, the average degradation rate was 0.32 mg / cm² / day.

[0029] Example 2

[0030] Alloy chemical composition (mass percentage): Gd 9.0%, Y 3.2%, Zn 2.0%, Zr 0.40%, balance Mg; unavoidable impurity elements: Fe 0.010%, Cu 0.007%, Ni 0.002%, Si 0.015%, total impurity content 0.034%.

[0031] The experimental materials were the same as those in Example 1.

[0032] Preparation process

[0033] (1) Raw material pretreatment: Preheat all raw materials to 180℃ and keep warm for 2 hours to remove moisture and oil; (2) Smelting: Under the protection of CO2+SF6 mixed gas, pure magnesium ingot, Mg-30Gd and Mg-30Y master alloy were added sequentially at 730℃ and stirred for 10min until melted; then pure zinc ingot and Mg-30Zr master alloy were added and stirred for 15min until uniform, and kept at the temperature for 20min. (3) Refining and settling: When the furnace temperature is raised to 750℃, add 2% of the total mass of the melt as a refining agent, stir for 20 minutes to refine, settling for 35 minutes, and remove the slag; (4) Casting: The furnace temperature is reduced to 700°C, and the molten metal is poured into a steel mold preheated to 200°C and air-cooled to obtain an ingot; (5) Solution treatment: The ingot is held at 515℃ for 10 hours and then quenched in hot water at 80℃; (6) Aging treatment: After quenching, the sample is kept at 200℃ for 60h and then air-cooled to room temperature to obtain the target sample.

[0034] Microstructure characterization shows that the alloy matrix is ​​an α-Mg solid solution with dispersed nano-precipitates and an average grain size of 10 μm.

[0035] Performance test results

[0036] (1) Room temperature mechanical properties: Tested according to the same standards as in Example 1, the tensile strength was 440 MPa, the yield strength was 320 MPa, and the elongation after fracture was 8.0%; (2) Corrosion resistance: The neutral salt spray test was conducted according to the same standard as in Example 1, and the neutral salt spray corrosion rate was measured to be 0.32 mg / cm² / day; (3) In vitro degradation performance: After immersion in simulated body fluid for 30 days, the average degradation rate was 0.30 mg / cm² / day.

[0037] Example 3

[0038] Alloy chemical composition (mass percentage): Gd 8.0%, Y 2.8%, Zn 1.5%, Zr 0.30%, balance Mg; unavoidable impurity elements: Fe 0.015%, Cu 0.009%, Ni 0.004%, Si 0.020%, total impurity content 0.048%.

[0039] The experimental materials were the same as those in Example 1.

[0040] Preparation process: (1) Raw material pretreatment: preheat all raw materials to 180℃ and keep warm for 2 hours to remove moisture and oil; (2) Smelting: Under the protection of CO2+SF6 mixed gas, pure magnesium ingot, Mg-30Gd and Mg-30Y master alloy were added sequentially at 720℃ and stirred for 10min until melted; then pure zinc ingot and Mg-30Zr master alloy were added and stirred for 15min until uniform, and kept at the temperature for 20min. (3) Refining and settling: When the furnace temperature is raised to 750℃, add 2% of the total mass of the melt as a refining agent, stir for 20 minutes to refine, settling for 35 minutes, and remove the slag; (4) Casting: The furnace temperature is reduced to 700°C, and the molten metal is poured into a steel mold preheated to 200°C and air-cooled to obtain an ingot; (5) Solution treatment: The ingot is held at 525℃ for 8 hours and then quenched in hot water at 80℃; (6) Aging treatment: After quenching, the sample is kept at 205℃ for 55h and then air-cooled to room temperature to obtain the target sample.

[0041] Microstructure characterization shows that the alloy matrix is ​​an α-Mg solid solution with uniformly distributed nano-precipitates and an average grain size of 15 μm.

[0042] Performance test results

[0043] (1) Room temperature mechanical properties: Tested according to the same standards as in Example 1, the tensile strength was 425 MPa, the yield strength was 305 MPa, and the elongation after fracture was 9.0%; (2) Corrosion resistance: The neutral salt spray test was conducted according to the same standard as in Example 1, and the neutral salt spray corrosion rate was measured to be 0.38 mg / cm² / day; (3) In vitro degradation performance: After immersion in simulated body fluid for 30 days, the average degradation rate was 0.35 mg / cm² / day.

[0044] Example 4

[0045] The alloy chemical composition (mass percentage) is the same as in Example 1: Gd 8.5%, Y 3.0%, Zn 1.8%, Zr 0.35%, with the balance being Mg; the impurity content is the same as in Example 1.

[0046] The experimental materials were the same as those in Example 1.

[0047] Preparation process: (1) The raw material pretreatment, smelting, refining and settling and casting process is completely consistent with that in Example 1, and alloy ingots are obtained; (2) Homogenization treatment: Place the ingot in a box furnace, keep it at 510℃ for 12 hours, and air cool it to room temperature to eliminate the segregation of the as-cast components; (3) Hot extrusion: The homogenized ingot is heated to 400℃ and held for 2 hours. It is then hot extruded using a horizontal extruder with an extrusion ratio of 16:1 and an extrusion rate of 0.5 m / min. After extrusion, it is air-cooled to room temperature to obtain extruded bar stock. (4) Solution treatment: Place the extruded bar in a box furnace and keep it at 520℃ for 8 hours. After taking it out, quickly transfer it to 80℃ hot water for quenching. (5) Aging treatment: The quenched bar is placed in a box furnace and kept at 200℃ for 48 hours. After being taken out, it is air-cooled to room temperature to obtain the target sample.

[0048] Microstructure characterization shows that the alloy undergoes dynamic recrystallization after hot extrusion, resulting in significantly refined grains with an average grain size of 3 μm, far below the technical requirement of ≤20 μm. The matrix is ​​an α-Mg solid solution, and the nano-precipitates are more uniformly and diffusely distributed without texture defects.

[0049] Performance test results

[0050] (1) Room temperature mechanical properties: Tested according to the same standard as in Example 1, the tensile strength was 465 MPa, the yield strength was 355 MPa, and the elongation after fracture was 12.5%. Compared with Example 1 in T6 state, the strength and plasticity were significantly improved simultaneously. (2) Corrosion resistance: The neutral salt spray test was conducted according to the same standard as in Example 1, and the neutral salt spray corrosion rate was measured to be 0.30 mg / cm² / day, indicating further improvement in corrosion resistance; (3) In vitro degradation performance: After 30 days of immersion in simulated body fluid, the average degradation rate was 0.28 mg / cm² / day, and the degradation controllability was better.

[0051] Example 5: Isothermal Forging Process

[0052] The alloy chemical composition (mass percentage) is the same as in Example 2: Gd 9.0%, Y 3.2%, Zn 2.0%, Zr 0.40%, with the balance being Mg; the impurity content is the same as in Example 2 and meets the limit requirements.

[0053] The experimental materials were the same as those in Example 1.

[0054] Preparation process: (1) Raw material pretreatment, smelting, refining and settling, casting process: completely consistent with Example 2, to obtain alloy ingots; (2) Homogenization treatment: Place the ingot in a box furnace, keep it at 515℃ for 12 hours, and air cool it to room temperature to eliminate the segregation of the as-cast components; (3) Isothermal forging: The homogenized ingot is heated to 400℃ and held for 2 hours. Isothermal forging is then performed using a hydraulic press. The forging temperature is maintained at 400℃ throughout the forging process, and the strain rate is 0.01s. -1 The total deformation was 60%, and the single-pass deformation was 10%. After forging, the sample was air-cooled to room temperature to obtain a forged sample. (4) Solution treatment: Place the forged sample in a box furnace and keep it at 515℃ for 8 hours. After taking it out, quickly transfer it to 80℃ hot water for quenching. (5) Aging treatment: The quenched sample is placed in a box furnace and held at 200℃ for 50 hours. After removal, it is air-cooled to room temperature to obtain the target sample, such as Figure 2 and 3 As shown.

[0055] Performance test results

[0056] (1) Room temperature mechanical properties: Tested according to the same standard as in Example 1, the tensile strength was 458 MPa, the yield strength was 348 MPa, and the elongation after fracture was 11.8%. Compared with Example 2 in T6 state, the strength and toughness were significantly improved simultaneously. (2) Corrosion resistance: The neutral salt spray test was conducted according to the same standard as in Example 1, and the neutral salt spray corrosion rate was measured to be 0.28 mg / cm² / day, indicating a significant improvement in corrosion resistance; (3) In vitro degradation performance: Fractures of weight-bearing bones in the lower limbs, such as the tibia, typically heal in 3-6 months. Therefore, biodegradable magnesium alloys used for bone fixation or repair need to maintain necessary mechanical support for at least several months and avoid rapid degradation before the bone tissue has completed initial healing. Based on this requirement, the corrosion rate of biodegradable magnesium alloys in simulated body fluids typically needs to be controlled below 0.5 mm / year to ensure effective support during a service life of at least 6 months.

[0057] From the perspective of specific material properties, the Mg-Zn-Gd-Y-Zr alloy exhibits a yield strength half-life of approximately 51 days in simulated body fluids, indicating that the alloy can maintain high residual strength in the early post-implantation period, sufficient to cover the mechanical stability requirements of the initial fracture healing stage. Its elongation half-life is approximately 20 days, suggesting that the material's plasticity decays faster than its strength, but the overall strength retention time still meets the early fixation needs of bone healing. On the other hand, the complete in vivo degradation period of WE43 magnesium alloy is approximately 12-24 months, significantly longer than the conventional healing time of 3-6 months for lower limb weight-bearing bones, thus covering the bone healing and subsequent bone remodeling stages. Furthermore, WE43 alloy showed degradation behavior adapted to the bone remodeling process in sheep models at 6 and 24 weeks, indicating that its in vivo degradation process is not excessively rapid but rather maintains a good time-matching relationship with the bone tissue repair and reconstruction process.

[0058] The performance of the above embodiments and comparative examples (Comparative Example 1 is AZ91D, Comparative Example 2 is WE43) was tested, and the test results are shown in Tables 1-3.

[0059] Table 1

[0060] Table 2 Initial mechanical properties of commercially available comparative alloys

[0061] Table 3. Strength decay data of other magnesium alloys in simulated body fluids.

[0062] In summary, the tensile strength and yield strength of all embodiments of this invention are more than 69% higher than those of commercial AZ91D and WE43 magnesium alloys, and the improvement in the hot deformation process embodiments exceeds 80%, completely solving the core pain point of insufficient strength of existing commercial magnesium alloys and their inability to meet the requirements of load-bearing bone implantation. The elongation of all embodiments of this invention is ≥8%, and the elongation of the hot deformation process embodiments exceeds 11%, which is far higher than that of commercial magnesium alloys, combining high strength and high toughness, avoiding the risk of brittle fracture during implantation. The corrosion resistance of all embodiments of this invention meets the technical requirements, and the corrosion resistance of the hot deformation process embodiments is comparable to that of commercial WE43 magnesium alloy and far superior to existing high-strength magnesium alloys. At the same time, it solves the problem of local pitting corrosion that is prone to occur in existing commercial magnesium alloys, achieving uniform and controllable degradation. The alloy of this invention does not contain controversial elements such as Al, and its biocompatibility is far superior to that of Al-containing AZ91D magnesium alloy, fully meeting the safety requirements of medical orthopedic implantation.

[0063] Specifically, the alloy of this invention has a tensile strength of 427–463 MPa and an 80% residual value of 342–370 MPa, which is still higher than the initial strength of WE43 (260 MPa) and AZ91D (250 MPa); the neutral salt spray corrosion rate is only 0.28–0.38 mg / cm² / day, which is much lower than most biodegradable magnesium alloys; there is no local pitting corrosion, avoiding a sharp drop in strength due to local perforation, and the degradation process is stable; the Mg-10Gd alloy shows good osseointegration and no element accumulation in vivo for 8 weeks; the optimized yield strength of the Mg-Gd-Y-Zn-Zr system is >300 MPa and the elongation is >10%; 3–6 months is the critical period for the healing of load-bearing bones, and the low corrosion rate and high initial strength of the alloy of this invention are sufficient to maintain effective mechanical support during this period. In addition, the AZ91D cell survival rate of L929 fibroblasts was only 60%-70% as measured by the CCK-8 method, while the magnesium alloy of the present invention was tested and found to achieve a cell survival rate of over 90%, thus exhibiting better biocompatibility.

[0064] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A high-strength, corrosion-resistant magnesium alloy for orthopedic implants, characterized in that, The magnesium alloy has the following chemical composition by mass percentage: Gd 7.8%-9.5%, Y 2.5%-3.6%, Zn 1.2%-2.5%, Zr 0.25%-0.50%, with the balance being Mg and unavoidable impurity elements; among the impurity elements, Fe≤0.02%, Cu≤0.02%, Ni≤0.02%, Si≤0.03%, and the total mass percentage of impurity elements ≤0.3%; The magnesium alloy has a multiphase structure with an α-Mg solid solution matrix. After T6 heat treatment, nanoscale precipitates are formed with an average grain size ≤20μm.

2. The high-strength, corrosion-resistant magnesium alloy for orthopedic implants according to claim 1, characterized in that, The chemical composition of the magnesium alloy, by mass percentage, includes: 8.5% Gd, 3.0% Y, 1.8% Zn, 0.35% Zr, with the balance being Mg and unavoidable impurity elements.

3. A method for preparing a high-strength, corrosion-resistant magnesium alloy for orthopedic implants as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Raw material pretreatment: Preheat pure magnesium ingots, Mg-Gd master alloy, Mg-Y master alloy, pure zinc ingots, and Mg-Zr master alloy to 150℃-200℃ to remove surface moisture from the raw materials. S2. Melting: Under the protective atmosphere of a mixed gas of CO2 and SF6, at 700℃-750℃, pretreated pure magnesium ingots, Mg-Gd master alloy, Mg-Y master alloy, pure zinc ingots and Mg-Zr master alloy are added in sequence, stirred evenly and kept at the temperature. S3. Refining and settling: At 740℃-760℃, add KCl-CaCl2-BaCl2-CaF2-YCl3 refining agent to the melt after smelting, stir for 15-25 minutes, and then let stand for 30-40 minutes to complete the purification of the melt. S4. Casting: Remove the slag from the surface of the melt and pour the melt into a metal mold preheated to 180℃-220℃ at 690℃-710℃ to obtain an ingot. S5. Solution treatment: The ingot is solution treated at 510℃-525℃ for 8-12 hours, and then quenched in 80℃ hot water. S6. Aging treatment: The quenched ingot is aged at 200℃-205℃ for 55-65 hours, and then air-cooled to obtain magnesium alloy.

4. The method for preparing the high-strength, corrosion-resistant magnesium alloy for orthopedic implants according to claim 3, characterized in that, In step S1, the Mg-Gd master alloy is a Mg-30Gd master alloy, the Mg-Y master alloy is a Mg-30Y master alloy, and the Mg-Zr master alloy is a Mg-30Zr master alloy.

5. The method for preparing the high-strength, corrosion-resistant magnesium alloy for orthopedic implants according to claim 3, characterized in that, In step S5, the solution treatment temperature is 515℃-520℃, and the treatment time is 8-10 hours.

6. The method for preparing the high-strength, corrosion-resistant magnesium alloy for orthopedic implants according to claim 3, characterized in that, In step S6, the aging treatment temperature is 200℃-205℃, and the treatment time is 55-60 hours.

7. The use of the high-strength corrosion-resistant magnesium alloy for orthopedic implants as described in claim 1 or 2 in the preparation of orthopedic implants.

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