High-corrosion-resistant medical rare earth magnesium alloy, preparation method and application thereof

Abstract

This invention belongs to the field of medical magnesium alloy surface modification technology, specifically relating to a high corrosion-resistant medical rare earth magnesium alloy, its preparation method, and its applications. The magnesium alloy provided in this invention is composed of the following chemical components by weight percentage: 3.50%–6.50% Gd, 0.75%–1.30% Zn, 0.84%–1.56% Y, 0.45%–0.78% Sc, with the balance being Mg. This invention prepares a high-performance corrosion barrier layer on the magnesium alloy surface through cladding rolling, annealing, chemical conversion, and electro-pulse deposition. By synergistically controlling key processes such as pulse frequency, conversion temperature, current density, and ion concentration, the overall protective performance of the film layer is significantly improved. The coating obtained by this invention is dense and has strong adhesion, excellent corrosion resistance, and particularly strong adaptability to product shapes, solving the problems of poor corrosion resistance, uneven corrosion, and severe bubble aggregation in traditional magnesium alloys under physiological conditions.

Description

Technical Field

[0001] This invention belongs to the field of medical magnesium alloy surface modification technology, and specifically relates to a high corrosion-resistant medical rare earth magnesium alloy, its preparation method and application. Background Technology

[0002] To overcome the shortcomings of traditional medical metal materials in terms of service performance (such as inability to degrade spontaneously in vivo, the need for secondary surgery, high cost, and the release of toxic ions), novel biodegradable medical metal materials have emerged in recent years and become a cutting-edge research direction in this field. Ideal medical materials should possess the following characteristics: a matched degradation rate, good biocompatibility, excellent mechanical properties, and the ability to promote tissue regeneration. Among many medical metals, magnesium alloys have attracted attention due to their unique comprehensive advantages (avoiding stress shielding effects, high bioactivity, strong compatibility, and spontaneous degradation), and are considered an ideal choice for next-generation medical implant materials. However, their excessively rapid degradation rate severely restricts their widespread clinical application.

[0003] To address the problem of poor corrosion resistance, surface modification technologies (such as mechanical polishing, fluorination, electroplating, and micro-arc oxidation) are considered effective ways to improve performance. However, current research also has many shortcomings: 1) Existing surface modification technologies are mostly concentrated on single film layers, and these films generally have defects such as microcracks and incomplete coverage, failing to provide long-term effective protection; 2) The film layers have limited functional properties and cannot simultaneously meet the multiple requirements of corrosion resistance and bioactivity. For example, the preparation process in patent CN201611243442.4 is simple and easy to control, with low production costs, and the resulting surface coating has characteristics such as dense structure and strong adhesion. However, it suffers from the problem of long-term protection being limited by ion exchange efficiency, and the durability of protection of a single structural layer may weaken under harsh body fluid environments. Although the surface coating in patent CN202311166207.1 has characteristics such as strong adhesion, high hardness, and few coating defects, this patent uses a combination of sandblasting pretreatment and micro-arc oxidation, which places high demands on sandblasting parameters and electrolyte composition ratios. The process control is difficult during large-scale production due to its stringent requirements, and the multi-step processing also increases the complexity of the production process. Another patent, CN201810158458.8, describes a bifunctional magnesium alloy coating with bisphosphate drug and nano-silver properties. Although it has the characteristics of low defect density, dense and crack-free structure, and strong adhesion, the cost of obtaining silver nitrate, the raw material for the coating, is relatively high, which puts pressure on large-scale production. Moreover, this patent uses a hydrothermal reaction method to prepare the coating, which has a long reaction cycle. Therefore, there is an urgent need for a method to prepare a high corrosion-resistant medical rare earth magnesium alloy to overcome the above-mentioned problems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a highly corrosion-resistant medical rare-earth magnesium alloy, its preparation method, and its applications. This method innovatively develops a selenium / phosphate-manganese / zinc composite film system with a dual-layer structure through a process of "cladding rolling + annealing + chemical conversion + electro-pulse deposition," significantly improving service performance through a dual-layer synergistic protection mechanism. This technology not only facilitates the simultaneous improvement of the overall mechanical properties of the product but also offers strong adaptability to component shapes, reducing initial equipment investment costs and the risk of errors in process connections, thus providing technical support for the clinical application of complex medical magnesium alloy components.

[0005] To solve the above-mentioned technical problems, this invention provides a method for preparing a highly corrosion-resistant medical rare earth magnesium alloy, comprising the following steps: Magnesium alloys were obtained by smelting and casting Mg-10%Gd, Mg-15%Y, Mg-8%Sc, pure magnesium, and pure zinc as raw materials. The mass ratio of Gd to Zn in the raw materials was 5.0~6.0:1, the mass ratio of Y to Zn was 1.2~1.3:1, and the mass ratio of Y to Sc was 2:1. After the cast magnesium alloy is clad in a billet, it is first held at 380℃~420℃ for 30min~60min, and then rolled in multiple passes at a rolling speed of 0.05m / s~0.20m / s. After rolling, it is annealed at 250℃~280℃ for 4h~6h and cooled to obtain annealed magnesium alloy. The deformation of a single pass is 20%~35%, and the total deformation is 70%~85%. Each pass is rolled at 90° alternating angles. Annealed magnesium alloy is polished and treated with alkaline solution, then reacted in a conversion solution with pH 2.0-2.5 for 500-1000 seconds, and then allowed to stand in a conversion solution heated to 60-80℃ for 10-30 minutes to obtain a surface chemically converted magnesium alloy. The conversion solution consists of 2-4 g / L Na3PO4. 4· It is prepared by mixing 12H2O with 2g / L~4g / L Ca(NO3)2·4H2O and 1g / L~1.5g / L SeO2 in a volume ratio of 1:1:0.5; A highly corrosion-resistant medical-grade rare-earth magnesium alloy was obtained by electro-pulse deposition treatment of a Zn-Mn system electrodeposition solution on a surface chemically transformed magnesium alloy. The current density of the electro-pulse deposition treatment was 0.2 A / cm². -2 ~0.8Acm -2 The pulse frequency is 600Hz to 1200Hz, the duty cycle is 10% to 30%, the electrolytic deposition temperature is 10℃ to 40℃, and the deposition time is 10min to 30min.

[0006] Preferably, the preparation steps of the as-cast magnesium alloy are as follows: Magnesium alloy was placed in a vacuum of 1×10⁻⁶. -2 In a vacuum environment, a mixture of SF6 and CO2 gas is introduced into the vacuum environment, and the mixture is smelted at 720℃~750℃. The mixture is then cooled to 710℃~720℃ for casting. After cooling, a cast magnesium alloy is obtained. The volume percentage of SF6 in the mixture of SF6 and CO2 gas is 0.2%~0.5%.

[0007] Preferably, the deformation per single pass is 20% to 35%, the total deformation per pass is 70% to 85%, and each pass is rolled alternately at 90°.

[0008] Preferably, the steps for treating the cast magnesium alloy with a billet sheath are as follows: A cast magnesium alloy is wrapped around a blank with a thickness of 8mm to 10mm, a chamfer of R3 to R5, and a surface roughness Ra < 1.6μm. The cast magnesium alloy wrapped around the blank is then placed inside a sleeve with a thickness of 0.05mm to 0.10mm of graphite paper on the inner wall. The thickness of the sleeve is 0.4mm to 0.6mm, and the gap between the inner wall of the sleeve and the cast magnesium alloy wrapped around the blank is ≤ 0.5mm.

[0009] Preferably, the sleeve is made of two materials: the upper part of the sleeve is made of 7050 aluminum alloy foil, and the lower part of the sleeve is made of 6061 aluminum alloy foil.

[0010] Preferably, the grinding and alkaline treatment steps of the annealed magnesium alloy are as follows: The annealed magnesium alloy was polished stepwise with SiC sandpaper ranging from 1000# to 4000#. After polishing, the annealed magnesium alloy was alkaline washed in an alkaline solution at 50℃~70℃ for 10min~40min, then rinsed with deionized water and dried with cold air. The alkaline solution was prepared by mixing 50g / L~70g / L NaOH and 10g / L~30g / L Na3PO4.

[0011] Preferably, the Zn-Mn system alloy electrodeposition treatment solution is prepared by mixing 30 g / L to 50 g / L sodium citrate, 5 g / L to 10 g / L Zn(NO3)2 and 30 g / L to 50 g / L MnSO4, and the pH value is adjusted to 1 to 10 by adding a dilute sulfuric acid solution with a concentration of 8% to 15% to the prepared Zn-Mn system electrodeposition treatment solution.

[0012] This invention provides a method for preparing a highly corrosion-resistant medical rare earth magnesium alloy.

[0013] Preferably, the high corrosion-resistant medical rare earth magnesium alloy is made of the following chemical composition by weight percentage: 3.50% to 6.50% Gd, 0.75% to 1.30% Zn, 0.84% ​​to 1.56% Y, 0.45% to 0.78% Sc, with the balance being Mg.

[0014] This invention discloses the application of a highly corrosion-resistant medical rare earth magnesium alloy in medical implant materials.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention involves smelting and casting Mg-10%Gd, Mg-15%Y, Mg-8%Sc, pure magnesium, and pure zinc as raw materials. The resulting as-cast magnesium alloy is then processed using an integrated synergistic process of cladding rolling, annealing, chemical conversion, and electroporation. This process innovatively forms a selenium / phosphate-manganese / zinc composite film system with a double-layer structure on the alloy surface, improving the overall mechanical properties of the high corrosion-resistant medical rare-earth magnesium alloy. Furthermore, through synergistic optimization of key process parameters such as chemical conversion temperature, time, and electrodeposition current density, microcracks and grooves in the composite film system on the alloy surface are repaired, enhancing the integrity of the coating. This solves the defects of microcracks and incomplete coverage present in traditional films, effectively controlling the surface microstructure, density, and bonding strength of the composite film system of the high corrosion-resistant medical rare-earth magnesium alloy. The overall protective performance and service life of the high corrosion-resistant medical rare-earth magnesium alloy composite film system are significantly improved. Moreover, this invention innovatively incorporates a Se-containing conversion layer during the chemical conversion, further enhancing the material's biocompatibility. More importantly, this process has low requirements for product shape and can be used for materials with complex irregular end face structures. Furthermore, the coating quality can be improved by adjusting the current and electroplating time, thereby enhancing the corrosion resistance of the alloy.

[0016] This invention, through the innovative design of scientifically introducing bioactive selenium and combining it with an electrolytic zinc-manganese layer, yields a membrane that is complete and uniform with few micro-defects and strong adhesion to the substrate. It successfully solves the technical challenge of traditional biomedical membranes in simultaneously achieving bioactivity and corrosion resistance, realizing a dual breakthrough in both practical function and bioefficacy, and providing more comprehensive performance support for its clinical application.

[0017] The process system employed in this invention is simple and efficient, significantly shortening the production cycle and reducing initial equipment investment costs and the risk of errors in process connections. In particular, this technology is highly adaptable to product shapes, exhibits excellent corrosion resistance, and solves the problems of rapid corrosion, uneven corrosion, and severe bubble aggregation in traditional medical magnesium alloys under physiological conditions. Attached Figure Description

[0018] Figure 1The surface microstructure of the alloy obtained in Example 1 after immersion in Hank's simulated body fluid for 7 days is shown.

[0019] Figure 2 The surface microstructure of the alloy obtained in Example 2 after immersion in Hank's simulated body fluid for 7 days is shown.

[0020] Figure 3 The surface microstructure of the alloy obtained in Example 3 after immersion in Hank's simulated body fluid for 7 days is shown. Detailed Implementation

[0021] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0022] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in Examples 1 to 5, preferred embodiments are described to avoid redundancy. However, this invention is not limited to these, but can be implemented in other ways within the scope of the technical solutions defined in the appended claims. All raw materials, reagents, instruments, and equipment used in the following embodiments of this invention can be purchased commercially or prepared using existing methods.

[0023] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Example 1 This embodiment 1 provides a method for preparing a highly corrosion-resistant medical rare earth magnesium alloy, including the following steps: S1. Using Mg-10%Gd, Mg-15%Y, Mg-8%Sc, pure magnesium, and pure zinc as raw materials, place them under a vacuum of 1×10⁻⁶. -2In a vacuum environment, a mixture of SF6 and CO2 gas is introduced into the vacuum environment, and the mixture is melted at 730°C. The temperature is then lowered to 710°C for casting. After cooling, a cast magnesium alloy is obtained. The volume percentage of SF6 in the SF6 and CO2 mixture is 0.3%. The alloy is then cooled to room temperature and melted and cast again to obtain a cast magnesium alloy. The raw material ratio satisfies the following conditions: the chemical weight ratio of Gd / Zn is 5:1, the chemical weight ratio of Y / Zn is 1.2:1, and the mass ratio of Y / Sc is 2:1.

[0025] S2. A 10mm thick blank with a chamfer of R5 and a surface roughness of 1.5μm is wrapped around a cast magnesium alloy. The cast magnesium alloy wrapped around the blank is then placed inside an aluminum alloy foil sheath with an inner wall of 0.10mm thick graphite paper. The aluminum alloy foil sheath is 0.5mm thick, and the gap between the inner wall of the aluminum alloy foil sheath and the cast magnesium alloy blank is ≤0.5mm. The blank is held at 420℃ for 60min, and then rolled in multiple passes at a rolling rate of 0.05m / s. The deformation per pass is controlled at 20%, and the total deformation is 75%. Each pass is rolled alternately at 90°. After rolling, the blank is annealed at 280℃ for 4h and then water-cooled to obtain an annealed magnesium alloy. The upper material of the aluminum alloy foil sheath is 7050 aluminum alloy foil, and the lower material of the sheath is 6061 aluminum alloy foil.

[0026] S3. Before conversion, the annealed magnesium alloy is successively polished with 1000# to 4000# SiC sandpaper. After polishing, the annealed magnesium alloy is alkaline washed in an alkaline solution at 55℃ for 25 minutes, rinsed with deionized water, and then dried with cold air. The alkaline solution is prepared by 50 g / L NaOH and 10 g / L Na3PO4. The alkaline-washed annealed magnesium alloy is reacted in a conversion solution at pH 2.0 for 600 seconds, and then the conversion solution is heated to 65℃ and allowed to stand for 10 minutes to obtain a surface chemically converted magnesium alloy. The chemical conversion solution is prepared by 2 g / L Na3PO4·12H2O, 2 g / L Ca(NO3)2·4H2O, and 1.5 g / L SeO2 in a volume ratio of 1:1:0.5.

[0027] S4. Surface-chemically transformed magnesium alloy was subjected to pulsed electrodeposition in a Zn-Mn electrodeposition solution to obtain a highly corrosion-resistant medical-grade rare-earth magnesium alloy. The Zn-Mn electrodeposition solution was prepared by mixing 30 g / L sodium citrate, 5 g / L Zn(NO3)2, and 30 g / L MnSO4. A 10% dilute sulfuric acid solution was added dropwise to adjust the pH to 4. The pulsed electrodeposition current density was 0.4 Acm. -2The pulse frequency was 600Hz, the duty cycle was 20%, the electrolytic deposition temperature was 30℃, and the deposition time was 30min.

[0028] The chemical composition by weight percentage of a high corrosion-resistant medical magnesium alloy prepared in this embodiment is: 3.75% Gd, 0.75% Zn, 0.90% Y, 0.45% Sc, with the balance being Mg.

[0029] Example 2 This embodiment 2 provides a method for preparing a highly corrosion-resistant medical rare earth magnesium alloy, including the following steps: S1. Using Mg-10%Gd, Mg-15%Y, Mg-8%Sc, pure magnesium, and pure zinc as raw materials, place them under a vacuum of 1×10⁻⁶. -2 In a vacuum environment, a mixture of SF6 and CO2 gas is introduced into the vacuum environment, and the mixture is melted at 750°C. The temperature is then lowered to 710°C for casting. After cooling, a cast magnesium alloy is obtained. The volume percentage of SF6 in the SF6 and CO2 mixture is 0.4%. The alloy is then cooled to room temperature and melted and cast again to obtain a cast magnesium alloy. The raw material ratio satisfies the following conditions: the chemical weight ratio of Gd / Zn is 5:1, the chemical weight ratio of Y / Zn is 1.2:1, and the mass ratio of Y / Sc is 2:1.

[0030] S2. A cast magnesium alloy is wrapped around a billet with a thickness of 8.85 mm, a chamfer of R5, and a surface roughness of 1.2 μm. The cast magnesium alloy wrapped around the billet is then placed inside an aluminum alloy foil sheath with an inner wall of graphite paper thickness of 0.10 mm and a thickness of 0.5 mm. The gap between the inner wall of the aluminum alloy foil sheath and the cast magnesium alloy billet is ≤0.5 mm. The sheath is held at 405℃ for 60 min, and then rolled in multiple passes at a rolling speed of 0.1 m / s, controlling the deformation per pass to 30% and the total deformation to 78%. Each pass is rolled alternately at 90°. After rolling, the sheath is annealed at 260℃ for 4 h and then water-cooled to obtain an annealed magnesium alloy. The upper end of the aluminum alloy foil sheath is made of 7050 aluminum alloy foil, and the lower end is made of 6061 aluminum alloy foil.

[0031] S3. Before conversion, the annealed magnesium alloy is successively polished with 1000# to 4000# SiC sandpaper. After polishing, the annealed magnesium alloy is alkaline washed in an alkaline solution at 70℃ for 30 minutes, rinsed with deionized water, and then dried with cold air. The alkaline solution is prepared by 50 g / L NaOH and 10 g / L Na3PO4. The alkaline-washed annealed magnesium alloy is reacted in a conversion solution at pH 2.5 for 800 seconds, and then the conversion solution is heated to 70℃ and allowed to stand for 15 minutes to obtain a surface chemically converted magnesium alloy. The chemical conversion solution is prepared by 2 g / L Na3PO4·12H2O, 2 g / L Ca(NO3)2·4H2O, and 1.5 g / L SeO2 in a volume ratio of 1:1:0.5.

[0032] S4. Surface-chemically transformed magnesium alloy was subjected to pulsed electrodeposition in a Zn-Mn electrodeposition solution to obtain a highly corrosion-resistant medical-grade rare-earth magnesium alloy. The Zn-Mn electrodeposition solution was prepared by mixing 30 g / L sodium citrate, 5 g / L Zn(NO3)2, and 30 g / L MnSO4. A 10% dilute sulfuric acid solution was added dropwise to adjust the pH to 4.5. The pulsed electrodeposition current density was 0.3 A / cm². -2 The pulse frequency was 800Hz, the duty cycle was 20%, the electrolytic deposition temperature was 30℃, and the deposition time was 30min.

[0033] The chemical composition by weight percentage of a high corrosion-resistant medical magnesium alloy prepared in this embodiment is: 4.15% Gd, 0.83% Zn, 0.996% Y, 0.498% Sc, with the balance being Mg.

[0034] Example 3 This embodiment provides a method for preparing a highly corrosion-resistant medical rare earth magnesium alloy, including the following steps: S1. Using Mg-10%Gd, Mg-15%Y, Mg-8%Sc, pure magnesium, and pure zinc as raw materials, place them under a vacuum of 1×10⁻⁶. -2 In a vacuum environment, a mixture of SF6 and CO2 gas is introduced into the vacuum environment, and the mixture is melted at 740°C. The temperature is then lowered to 710°C for casting. After cooling, a cast magnesium alloy is obtained. The volume percentage of SF6 in the SF6 and CO2 mixture is 0.5%. The alloy is then cooled to room temperature and melted and cast again to obtain a cast magnesium alloy. The raw material ratio satisfies the following conditions: the chemical weight ratio of Gd / Zn is 6:1, the chemical weight ratio of Y / Zn is 1.3:1, and the mass ratio of Y / Sc is 2:1.

[0035] S2. A cast magnesium alloy is wrapped around a billet with a thickness of 8.65 mm, a chamfer of R5, and a surface roughness of 1.2 μm. The cast magnesium alloy wrapped around the billet is then placed inside an aluminum alloy foil sheath with an inner wall of graphite paper thickness of 0.10 mm and a thickness of 0.5 mm. The gap between the inner wall of the aluminum alloy foil sheath and the cast magnesium alloy billet is ≤0.5 mm. The sheath is held at 400℃ for 60 min, and then rolled in multiple passes at a rolling speed of 0.15 m / s, controlling the deformation per pass to 30% and the total deformation to 85%. Each pass is rolled alternately at 90°. After rolling, the sheath is annealed at 250℃ for 5 h and then water-cooled to obtain an annealed magnesium alloy. The upper end of the aluminum alloy foil sheath is made of 7050 aluminum alloy foil, and the lower end is made of 6061 aluminum alloy foil.

[0036] S3. Before conversion, the annealed magnesium alloy is successively polished with 1000# to 4000# SiC sandpaper. After polishing, the annealed magnesium alloy is alkaline washed in an alkaline solution at 70℃ for 40 minutes, rinsed with deionized water, and then dried with cold air. The alkaline solution is prepared by 65 g / L NaOH and 30 g / L Na3PO4. The alkaline-washed annealed magnesium alloy is reacted in a conversion solution at pH 2.5 for 1000 seconds, and then the conversion solution is heated to 80℃ and allowed to stand for 15 minutes to obtain a surface chemically converted magnesium alloy. The chemical conversion solution is prepared by 3 g / L Na3PO4·12H2O, 3 g / L Ca(NO3)2·4H2O, and 1.5 g / L SeO2 in a volume ratio of 1:1:0.5.

[0037] S4. The surface-chemically transformed magnesium alloy was subjected to pulsed electrodeposition in a Zn-Mn electrodeposition solution to obtain a highly corrosion-resistant medical-grade rare-earth magnesium alloy. The Zn-Mn electrodeposition solution was prepared by mixing 45 g / L sodium citrate, 8 g / L Zn(NO3)2, and 30 g / L MnSO4. A 10% dilute sulfuric acid solution was added dropwise to adjust the pH to 5.1. The pulsed electrodeposition current density was 0.6 A / cm². -2 The pulse frequency was 900 Hz, the duty cycle was 30%, the electrolytic deposition temperature was 35℃, and the deposition time was 30 min.

[0038] The chemical composition by weight percentage of a high corrosion-resistant medical magnesium alloy prepared in this embodiment is: 6.12% Gd, 1.02% Zn, 1.326% Y, 0.663% Sc, with the balance being Mg.

[0039] Example 4 This embodiment provides a method for preparing a highly corrosion-resistant medical rare earth magnesium alloy, including the following steps: S1. Using Mg-10%Gd, Mg-15%Y, Mg-8%Sc, pure magnesium, and pure zinc as raw materials, place them under a vacuum of 1×10⁻⁶. -2 In a vacuum environment, a mixture of SF6 and CO2 gas is introduced into the vacuum environment, and the mixture is melted at 720°C. The temperature is then lowered to 715°C for casting. After cooling, a cast magnesium alloy is obtained. The volume percentage of SF6 in the SF6 and CO2 mixture is 0.2%. The alloy is then cooled to room temperature and melted and cast again to obtain a cast magnesium alloy. The raw material ratio satisfies the following conditions: the chemical weight ratio of Gd / Zn is 5:1, the chemical weight ratio of Y / Zn is 1.2:1, and the chemical mass ratio of Y / Sc is 2:1.

[0040] S2. A cast magnesium alloy is wrapped around a billet with a thickness of 8 mm, a chamfer of R4, and a surface roughness of 1.5 μm. The cast magnesium alloy wrapped around the billet is then placed inside an aluminum alloy foil sheath with an inner wall of graphite paper thickness of 0.05 mm and a thickness of 0.4 mm. The gap between the inner wall of the aluminum alloy foil sheath and the cast magnesium alloy billet is ≤0.5 mm. The sheath is held at 380℃ for 30 min, and then rolled in multiple passes at a rolling speed of 0.10 m / s, controlling the deformation per pass to 35% and the total deformation to 70%. Each pass is rolled alternately at 90°. After rolling, the sheath is annealed at 270℃ for 5 h and then water-cooled to obtain an annealed magnesium alloy. The upper end of the aluminum alloy foil sheath is made of 7050 aluminum alloy foil, and the lower end is made of 6061 aluminum alloy foil.

[0041] S3. Before conversion, the annealed magnesium alloy is successively polished with 1000# to 4000# SiC sandpaper. After polishing, the annealed magnesium alloy is alkaline washed in an alkaline solution at 50℃ for 10 minutes, rinsed with deionized water, and then dried with cold air. The alkaline solution is prepared by 60 g / L NaOH and 20 g / L Na3PO4. The alkaline-washed annealed magnesium alloy is reacted in a conversion solution at pH 2.2 for 500 seconds, and then the conversion solution is heated to 60℃ and allowed to stand for 30 minutes to obtain a surface chemically converted magnesium alloy. The chemical conversion solution is prepared by 4 g / L Na3PO4·12H2O, 4 g / L Ca(NO3)2·4H2O, and 1 g / L SeO2 in a volume ratio of 1:1:0.5.

[0042] S4. The surface-chemically transformed magnesium alloy was subjected to pulsed electrodeposition in a Zn-Mn electrodeposition solution to obtain a highly corrosion-resistant medical-grade rare-earth magnesium alloy. The Zn-Mn electrodeposition solution was prepared by mixing 50 g / L sodium citrate, 10 g / L Zn(NO3)2, and 50 g / L MnSO4. An 8% dilute sulfuric acid solution was added dropwise to adjust the pH to 1. The pulsed current density for the electrodeposition treatment was 0.2 A / cm². -2 The pulse frequency was 1200 Hz, the duty cycle was 10%, the electrolytic deposition temperature was 10℃, and the deposition time was 10 min.

[0043] The chemical composition by weight percentage of a high corrosion-resistant medical magnesium alloy prepared in this embodiment is: 3.50% Gd, 0.70% Zn, 0.84% ​​Y, 0.42% Sc, with the balance being Mg.

[0044] Example 5 This embodiment provides a method for preparing a highly corrosion-resistant medical rare earth magnesium alloy, including the following steps: S1. Using Mg-10%Gd, Mg-15%Y, Mg-8%Sc, pure magnesium, and pure zinc as raw materials, place them under a vacuum of 1×10⁻⁶. -2 In a vacuum environment, a mixture of SF6 and CO2 gas is introduced into the vacuum environment, and the mixture is melted at 730°C. The temperature is then lowered to 720°C for casting. After cooling, a cast magnesium alloy is obtained. The volume percentage of SF6 in the SF6 and CO2 mixture is 0.5%. The alloy is then cooled to room temperature and melted and cast again to obtain a cast magnesium alloy. The raw material ratio satisfies the following conditions: the chemical weight ratio of Gd / Zn is 5.5:1, the chemical weight ratio of Y / Zn is 1.1:1, and the chemical mass ratio of Y / Sc is 2:1.

[0045] S2. A 9mm thick, R3 chamfered, and 1.5μm surface roughness billet is wrapped with a cast magnesium alloy. The cast magnesium alloy with the billet wrapped is then placed inside an aluminum alloy foil sleeve with a graphite paper thickness of 0.08mm on the inner wall. The aluminum alloy foil sleeve is 0.6mm thick, and the gap between the inner wall of the aluminum alloy foil sleeve and the cast magnesium alloy with the billet wrapped is ≤0.5mm. The mixture is held at 420℃ for 40min, and then rolled in multiple passes at a rolling speed of 0.2m / s. The deformation of each pass is controlled at 35%, and the total deformation of the rolling is 80%. Each pass is rolled alternately at 90°. After rolling, the mixture is annealed at 270℃ for 6h and water-cooled to obtain an annealed magnesium alloy. The upper material of the aluminum alloy foil sleeve is 7050 aluminum alloy foil, and the lower material of the sleeve is 6061 aluminum alloy foil.

[0046] S3. Before conversion, the annealed magnesium alloy is successively polished with 1000# to 4000# SiC sandpaper. After polishing, the annealed magnesium alloy is alkaline washed in an alkaline solution at 70℃ for 40 minutes, rinsed with deionized water, and then dried with cold air. The alkaline solution is prepared by 70 g / L NaOH and 30 g / L Na3PO4. The alkaline-washed annealed magnesium alloy is reacted in a conversion solution at pH 2.5 for 1000 seconds, and then the conversion solution is heated to 70℃ and allowed to stand for 30 minutes to obtain a surface chemically converted magnesium alloy. The chemical conversion solution is prepared by 3.5 g / L Na3PO4·12H2O, 3.5 g / L Ca(NO3)2·4H2O, and 1.2 g / L SeO2 in a volume ratio of 1:1:0.5.

[0047] S4. Surface-chemically transformed magnesium alloy was subjected to pulsed electrodeposition in a Zn-Mn electrodeposition solution to obtain a highly corrosion-resistant medical-grade rare-earth magnesium alloy. The Zn-Mn electrodeposition solution was prepared by mixing 35 g / L sodium citrate, 5 g / L Zn(NO3)2, and 45 g / L MnSO4. A 15% dilute sulfuric acid solution was added dropwise to adjust the pH to 10. The pulsed current density for the electrodeposition treatment was 0.8 A / cm². -2 The pulse frequency was 1000 Hz, the duty cycle was 10%, the electrolytic deposition temperature was 40℃, and the deposition time was 20 min.

[0048] The chemical composition by weight percentage of a high corrosion-resistant medical magnesium alloy prepared in this embodiment is: 6.50% Gd, 1.30% Zn, 1.56% Y, 0.78% Sc, with the balance being Mg.

[0049] All of the above Examples 1 to 5 can prepare highly corrosion-resistant medical magnesium alloys. The highly corrosion-resistant medical magnesium alloys prepared in Examples 1 to 3 are now preferred for corrosion resistance testing and morphology characterization testing in a simulated body fluid environment.

[0050] Figure 1 The image shows the surface microstructure of the alloy obtained in Example 1 after immersion in simulated body fluid for 7 days. Potentiodynamic polarization testing revealed that the corrosion current density of the alloy under simulated body fluid conditions was 45.83 μA·cm⁻¹. -2 The surface roughness after product removal was 7.76 μm. The results show that the surface-modified alloy not only has relatively excellent corrosion resistance, but also ensures a uniform corrosion process and a relatively flat overall surface corrosion profile (Sp=45 μm, Sv=71 μm), which is beneficial to maintaining the service performance of the alloy material in bulk.

[0051] Figure 2The image shows the surface microstructure of the alloy obtained in Example 2 after immersion in simulated body fluid for 7 days. Potentiodynamic polarization testing revealed that the corrosion current density of the alloy under simulated body fluid conditions was 40.61 μA·cm⁻¹. -2 The surface roughness after product removal was 7.03 μm. The results show that the surface-modified alloy not only has relatively excellent corrosion resistance, but also ensures a uniform corrosion process and a relatively flat overall surface corrosion profile (Sp=44 μm, Sv=65 μm), which is beneficial to maintaining the service performance of the alloy material in bulk.

[0052] Figure 3 The image shows the surface microstructure of the alloy obtained in Example 3 after immersion in simulated body fluid for 7 days. Potentiodynamic polarization testing revealed that the corrosion current density of the alloy under simulated body fluid conditions was 25.11 μA·cm⁻¹. -2 The surface roughness after product removal was 6.803 μm. The results show that the surface-modified alloy not only has relatively excellent corrosion resistance, but also ensures a uniform corrosion process and a relatively flat overall surface corrosion profile (Sp=41 μm, Sv=57 μm), which is beneficial to maintaining the service performance of the alloy material in bulk.

[0053] In summary, factors such as conversion temperature, conversion time, and electrodeposition density during the preparation process are closely related to the quality and corrosion resistance of the alloy surface film. This invention, through the synergistic control of key processes such as pulse frequency, conversion temperature, current density, and ion concentration, significantly improves the overall protective performance of the film, providing a clear, effective, and reliable technical solution to the problem of excessively rapid degradation of medical rare earth magnesium alloys.

Claims

1. A method for preparing a highly corrosion-resistant medical rare earth magnesium alloy, characterized in that, Includes the following steps: Magnesium alloys were obtained by smelting and casting Mg-10%Gd, Mg-15%Y, Mg-8%Sc, pure magnesium, and pure zinc as raw materials. The mass ratio of Gd to Zn in the raw materials was 5.0~6.0:1, the mass ratio of Y to Zn was 1.2~1.3:1, and the mass ratio of Y to Sc was 2:

1. After the cast magnesium alloy is clad in a billet, it is first held at 380℃~420℃ for 30min~60min, then rolled in multiple passes at a rolling speed of 0.05m / s~0.20m / s, and then annealed at 250℃~280℃ for 4h~6h, and then cooled to obtain the annealed magnesium alloy. Annealed magnesium alloy is polished and treated with alkaline solution, then reacted in conversion solution with pH 2.0~2.5 for 500s~1000s, and then allowed to stand in conversion solution heated to 60℃~80℃ for 10min~30min to obtain surface chemically converted magnesium alloy. The conversion solution is prepared by mixing 2g / L~4g / L Na3PO4·12H2O, 2g / L~4g / L Ca(NO3)2·4H2O and 1g / L~1.5g / L SeO2 in a volume ratio of 1:1:0.

5. A highly corrosion-resistant medical-grade rare-earth magnesium alloy was obtained by electro-pulse deposition treatment of a Zn-Mn system electrodeposition solution on a surface chemically transformed magnesium alloy. The current density of the electro-pulse deposition treatment was 0.2 A / cm². -2 ~0.8Acm -2 The pulse frequency is 600Hz to 1200Hz, the duty cycle is 10% to 30%, the electrolytic deposition temperature is 10℃ to 40℃, and the deposition time is 10min to 30min.

2. The method for preparing a high corrosion-resistant medical rare earth magnesium alloy according to claim 1, characterized in that, The preparation steps for as-cast magnesium alloys are as follows: Magnesium alloy raw materials were placed in a vacuum of 1×10⁻⁶. -2 In a vacuum environment, a mixture of SF6 and CO2 gas is introduced into the vacuum environment, and the mixture is smelted at 720℃~750℃. The mixture is then cooled to 710℃~720℃ for casting. After cooling, a cast magnesium alloy is obtained, wherein the volume percentage of SF6 in the mixture of SF6 and CO2 gas is 0.2%~0.5%.

3. The method for preparing a high corrosion-resistant medical rare earth magnesium alloy according to claim 1, characterized in that, The deformation per single pass is 20% to 35%, and the total deformation per pass is 70% to 85%. Each pass is rolled at 90° alternating angles.

4. The method for preparing a high corrosion-resistant medical rare earth magnesium alloy according to claim 1, characterized in that, The steps for cladding as-cast magnesium alloy blanks are as follows: A cast magnesium alloy is wrapped around a billet with a thickness of 8mm to 10mm, a chamfer of R3 to R5, and a surface roughness Ra < 1.6μm. The cast magnesium alloy wrapped around the billet is then placed inside a sleeve with a graphite paper layer of 0.05mm to 0.10mm thickness on the inner wall. The thickness of the sleeve is 0.4mm to 0.6mm, and the gap between the inner wall of the sleeve and the cast magnesium alloy wrapped around the billet is ≤ 0.5mm.

5. The method for preparing a high corrosion-resistant medical rare earth magnesium alloy according to claim 4, characterized in that, The sleeve is made of two materials: the upper part of the sleeve is made of 7050 aluminum alloy foil, and the lower part of the sleeve is made of 6061 aluminum alloy foil.

6. The method for preparing a high corrosion-resistant medical rare earth magnesium alloy according to claim 1, characterized in that, The grinding and alkaline treatment steps for the annealed magnesium alloy are as follows: The annealed magnesium alloy was polished stepwise with SiC sandpaper ranging from 1000# to 4000#. After polishing, the annealed magnesium alloy was alkaline washed in an alkaline solution at 50℃~70℃ for 10min~40min, then rinsed with deionized water and dried with cold air. The alkaline solution was prepared by mixing 50g / L~70g / L NaOH and 10g / L~30g / L Na3PO4.

7. The method for preparing a high corrosion-resistant medical rare earth magnesium alloy according to claim 1, characterized in that, The Zn-Mn alloy electrodeposition solution is prepared by mixing 30 g / L to 50 g / L sodium citrate, 5 g / L to 10 g / L Zn(NO3)2 and 30 g / L to 50 g / L MnSO4. A dilute sulfuric acid solution with a concentration of 8% to 15% is added dropwise to the prepared Zn-Mn alloy electrodeposition solution to adjust the pH value to 1 to 10.

8. The high corrosion-resistant medical rare earth magnesium alloy is prepared by the preparation method according to any one of claims 1 to 7.

9. The high corrosion-resistant medical rare earth magnesium alloy according to claim 8, characterized in that, This highly corrosion-resistant medical rare earth magnesium alloy is made of the following chemical composition by weight percentage: 3.50%–6.50% Gd, 0.75%–1.30% Zn, 0.84%–1.56% Y, 0.45%–0.78% Sc, with the balance being Mg.

10. The application of the high corrosion-resistant medical rare earth magnesium alloy according to claim 8 in medical implant materials.

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