High-toughness degradable zinc alloy and preparation method thereof

Abstract

The application belongs to the technical field of biomedically degradable metal material preparation, and particularly relates to a high-strength and high-toughness degradable zinc alloy and a preparation method thereof, which comprises the following components in percentage by weight: Mn 0.1-1%, Al 0.1-0.5%, Ce 0.01-0.12%, and the rest is Zn; the application has good strength, elongation and corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of biomedical biodegradable metal material preparation technology, specifically relating to a high-strength and tough biodegradable zinc alloy and its preparation method. Background Technology

[0002] Compared to traditional biodegradable iron-based and magnesium-based alloys, zinc-based biodegradable metallic materials offer good biocompatibility and a more suitable degradation rate, making them promising for applications in biomedical cardiovascular stent implants and bone repair. An ideal cardiovascular stent should possess excellent overall performance, requiring a tensile strength ≥350 MPa and an elongation ≥25%.

[0003] However, the mechanical properties of cast pure zinc and its hot-deformed form are poor, with tensile strength less than 180 MPa and elongation less than 2%, making it difficult to meet the requirements for use in medical cardiovascular stents. Currently, mechanical properties are mainly improved through alloying and subsequent plastic deformation. Common systems such as ZnMg, ZnLi, ZnMn, and ZnCu have good effects on improving strength or elongation. The highest strength medical zinc alloy system reported so far is Zn-0.8Li-0.4Mg, but its elongation is less than 5% (Yang H, et al. Nature Communications, 2020.11(1):1-16). The fracture elongation of Zn-(0.2~0.6%)Mn alloy can be as high as 48~71%, but the tensile strength is low, about 182~222 MPa (Sun S, et al. Materials Science and Engineering: A, 2017.701:129-133).

[0004] Besides the core issue of mismatched mechanical properties, most existing zinc alloy stent systems still face the problem of excessively rapid degradation. On the one hand, existing zinc alloys often suffer from coarse and unevenly distributed second phases, which easily form galvanic corrosion with the zinc matrix, leading to localized pitting corrosion and intergranular corrosion. This causes premature failure of local stent structures, and even overall stent collapse before vascular repair is complete. On the other hand, some alloy systems add excessive alloying elements to improve mechanical properties, resulting in an overall faster degradation rate. This may also exacerbate uneven degradation of the material, leading to severely insufficient radial support in the later stages of implantation, failing to meet the long-term support requirements after vascular implantation.

[0005] Chinese patent application publication number CN 107198796 A discloses a biomedical Zn Mn Cu-based zinc alloys and their preparation methods are described, in which the mass percentage of Mn ranges from 0.1% to 5% and the percentage of Cu ranges from 0.1% to 2%. However, the extruded tensile strength of this alloy is less than 300 MPa, making it unsuitable for use in cardiovascular stents requiring high support strength. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-strength and tough biodegradable zinc alloy and its preparation method, which has good strength, elongation and corrosion resistance.

[0007] This invention provides a high-strength and tough biodegradable zinc alloy comprising the following components by weight percentage: Mn 0.1~1%, Al 0.1~0.5%, Ce 0.01~0.12%, with the balance being Zn.

[0008] Preferably, it is composed of the following components in weight percentage: Mn 0.1~1%, Al 0.1~0.5%, Ce 0.01~0.12%, with the balance being Zn.

[0009] Preferably, the composition includes the following components by weight percentage: Mn 0.2~0.8%, Al 0.2~0.5%, Ce 0.05~0.12%, with the balance being Zn.

[0010] This invention provides a method for preparing the high-strength and tough biodegradable zinc alloy, wherein the zinc alloy ingot is homogenized, then hot extruded and deformed, subjected to multiple drawing and annealing alternating processes, and finally aged to obtain the high-strength and tough biodegradable zinc alloy.

[0011] Preferably, the zinc alloy ingot is smelted at a temperature of 800~860℃ during preparation.

[0012] Preferably, the homogenization process involves isostatic pressing under vacuum or inert gas protection at a temperature of 120-400°C; followed by water cooling. During isostatic pressing under inert gas protection, the pressure is 1-50 MPa.

[0013] Preferably, the temperature of the hot extrusion deformation is 200~300℃, and the extrusion ratio is 15~35:1.

[0014] Preferably, the drawing is performed at room temperature, with a drawing speed of 20-40 mm / s, an annealing temperature of 150-300℃, and a holding time of 60-120 min. As the number of drawing passes increases, the annealing temperature after each drawing pass gradually decreases, and the number of alternating drawing and annealing processes is not less than 5.

[0015] Preferably, the aging treatment temperature is 25~200 ℃, the holding time is 5~20 hours, and air cooling or water cooling is used.

[0016] Preferably, the treatment also includes surface modification after aging, wherein the surface modification method is one or more of surface carburizing, sandblasting, and passivation.

[0017] The beneficial effects of this invention are as follows: This invention utilizes the biodegradability of Zn and Zn alloys, selecting essential trace element Mn and appropriate amounts of Al and Ce as alloying elements to improve the mechanical properties of pure Zn. This invention exhibits a high work hardening rate, benefiting from the bimodal structure generated by the alternating distribution of ultrafine recrystallized grains and coarse deformed grains. The coarse grains are more prone to uniform twinning deformation, playing a good role in coordinating deformation through intergranular transfer. Furthermore, by altering the crystal orientation, it stimulates further crystal slip, improving the strength and work hardening rate of the Zn alloy. The proportion of recrystallized grains is within 62-78%. Secondly, the addition of appropriate amounts of rare earth Ce, which combines with Al and Zn respectively, forms finely dispersed intermetallic compounds (Al, Ce, and Ce). 11 Ce3 and CeZn 11 This achieves a good modification effect and significantly refines the grain size. Therefore, in the bimodal structure and Al of this invention 11 Ce3 and CeZn 11 Due to the synergistic effect of the phase particles, zinc alloys possess high strength, toughness, and work hardening ability.

[0018] This invention improves the microstructure of Zn alloys by adding Mn, Al, and Ce elements, based on appropriate alloying elements and proportions. The zinc alloy designed by this invention exhibits good strength and toughness. Within the effective range of alloying element content, its uniform elongation reaches 25-33%, and its tensile strength reaches 364-407 MPa. Furthermore, it exhibits a moderate degradation rate, effectively preventing fractures in Zn alloy implants due to excessive deformation at localized locations.

[0019] In this invention, Mn, a low-cost and essential trace element for the human body, is used as the primary alloying element. This effectively improves the strength and ductility of zinc alloys, providing solid solution strengthening and MnZn alloying. 13 The effect of the second phase enhancement.

[0020] The total content of alloying elements in the medical zinc alloy of this invention does not exceed 1.5%. While having good biocompatibility, it has a low manufacturing cost through a processing method that alternates between hot extrusion, drawing deformation and low-temperature annealing. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to some specific embodiments. Of course, these are merely examples and are not intended to limit the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention. These all fall within the scope of protection of this invention.

[0022] The testing standard for tensile strength and elongation is GB / T 228.1. 2010: Metallic materials, tensile testing at room temperature; corrosion rate testing standard is ASTM G31 72, the medium is Hank's reagent.

[0023] Example 1 This embodiment is a high-strength and tough biodegradable zinc alloy, comprising the following components by weight percentage: Mn 0.8%, Al 0.45%, Ce 0.12%, with the balance being Zn.

[0024] The preparation method of the biodegradable zinc alloy in this embodiment is as follows: 1) Batching: Weigh the ingredients according to the above composition. It should be noted that each element has different burn-off rates during the smelting process. Weigh the ingredients according to the burn-off rates of 3% for zinc, 1% for manganese, 1% for aluminum, and 7% for cerium.

[0025] 2) Smelting: Zinc-manganese master alloy (zinc and manganese in a 99.2:0.8 mass ratio, melted at 80°C, then cast into a graphite mold and allowed to cool naturally to room temperature) and aluminum-cerium master alloy (aluminum and cerium in an 80:20 mass ratio, melted at 860°C, then cast into a graphite mold and allowed to cool naturally to room temperature) are smelted separately in a vacuum induction furnace (melting temperature 850°C) under an argon atmosphere. The molten metal is then cast into a cylindrical inner cavity and gradually cooled to room temperature to form a zinc alloy ingot.

[0026] 3) Homogenization treatment: First, the surface layer of the above-mentioned ingot blank, 2.5 mm, is removed by machining to obtain a cylindrical ingot blank with a diameter of Φ55 mm. Then, the cast zinc alloy ingot is subjected to a vacuum degree of 1×10 -3 The zinc alloy was held at 290°C for 3 hours in a tubular annealing furnace, then heated to 320°C and held for 6 hours, and then cooled to room temperature in water to improve the segregation of elements in the zinc alloy.

[0027] 4) Hot extrusion: The extrusion ratio is 27:1, the extrusion temperature is 250 ℃, and a layer of graphite is evenly covered on the surface of the die as a lubricant before extrusion. After extrusion, an alloy rod with a diameter of Φ10.5 mm is obtained.

[0028] 5) Drawing and Low-Temperature Annealing: A sulfurized fatty acid ester coolant was used for surface cooling and lubrication during the drawing process. The drawing speed was 25 mm / s. After each drawing pass, the surface residue was cleaned, and the sample was then annealed in an furnace at 150–290 °C for 1.5 hours in an argon atmosphere. A total of 15 drawing passes were performed, resulting in zinc alloy bars with a diameter of Φ4.9–5.1 mm. The annealing temperature gradually decreased after each drawing pass, from 290 °C for the first pass to 150 °C for the final pass, representing a 10 °C temperature gradient between each pass.

[0029] 6) Aging treatment: The aging temperature is 90 ℃, the holding time is 10 hours, the protective atmosphere is argon, and the aging treatment is air-cooled to obtain aged zinc alloy rods.

[0030] 7) Surface modification: After the aged zinc alloy bar is laser-cut into shape, the surface of the component is polished and then surface modified. The surface modification method is passivation. The operation steps include: (1) Polishing treatment. Polishing is performed sequentially with 200, 600, 1000, 1500, 2000, 3000 and 5000 grit sandpaper, and then electrochemical polishing is performed to make the surface roughness Ra≤3.2. (2) Cleaning treatment. Chemical cleaning is used to remove impurities from the surface to ensure that the surface is clean. (3) Pickling treatment. Acetic acid is used to remove oxides and other impurities from the zinc alloy surface. The treatment time is 3~5 minutes. (4) Neutralization treatment. Sodium aqueous solution is used to neutralize the acidic substances remaining on the zinc alloy surface. The treatment time is 3~5 minutes. (5) Passivation treatment. Chromic acid is used for passivation to form a passivation film on the surface. The treatment time is 10~15 minutes. (6) Cleaning and drying. After cleaning the zinc alloy surface with water, it was dried in a drying oven at 40 ℃. This surface modification method improves the appearance of the zinc alloy surface, increases its corrosion resistance, and extends its service life.

[0031] Example 2 Example 2 differs from Example 1 in that it includes the following components by weight percentage: Mn 0.25%, Al 0.2%, Ce 0.05%, with the balance being Zn. Everything else is the same as in Example 1.

[0032] Example 3 Example 3 differs from Example 1 in that it includes the following components by weight percentage: Mn 0.5%, Al 0.3%, Ce 0.09%, with the balance being Zn. Everything else is the same as in Example 1.

[0033] Comparative Example 1 Compared with Example 1, Comparative Example 1 differs in that it includes the following components by weight percentage: Mn 0.8%, Al 0.45%, Ce 0.24%, with the balance being Zn. Everything else is the same as in Example 1.

[0034] Comparative Example 2 Compared with Example 1, Comparative Example 2 differs in that it includes the following components by weight percentage: Mn 0.8%, Al 0.45%, Ce 0%, with the balance being Zn. Everything else is the same as in Example 1.

[0035] Comparative Example 3 Compared with Example 1, Comparative Example 3 differs in that it includes the following components by weight percentage: Mn 0.8%, Al 0%, Ce 0%, with the balance being Zn. Everything else is the same as in Example 1.

[0036] Comparative Example 4 Compared with Example 1, Comparative Example 4 differs in that it includes the following components by weight percentage: Mn 0.8%, Al 0.05%, Ce 0.12%, with the balance being Zn. Everything else is the same as in Example 1.

[0037] Comparative Example 5 Compared with Example 1, Comparative Example 5 differs in that it includes the following components by weight percentage: Mn 0.8%, Al 0.45%, La 0.12%, with the balance being Zn. Everything else is the same as in Example 1.

[0038] Comparative Example 6 Compared with Example 1, Comparative Example 6 differs in that the annealing temperature remains unchanged after each drawing pass and is 200°C during the drawing and low-temperature annealing processes. Everything else is the same as in Example 1.

[0039] Table 1 compares the room temperature tensile strength and uniform elongation experimental results of Examples 1-3 and Comparative Examples 1-6.

[0040] Table 1. Experimental results of tensile strength, uniform elongation, and corrosion rate of the examples and comparative examples.

[0041] In Example 1, the proportion of fine grains in the zinc alloy is within 62-78%. The reason for its high strength and uniform elongation is also due to the bimodal structure of alternating coarse and fine grains and the dispersed distribution of small-sized Al particles. 11The synergistic effect of Ce3 degeneration. Therefore, its excellent performance can meet the mechanical performance requirements of cardiovascular stent applications.

[0042] As can be seen from Examples 1-3 and Comparative Examples 1-6, the preparation process of the Zn-Mn-Al-Ce alloy material of the present invention is relatively simple. Through reasonable alloying and subsequent preparation processes, a bimodal structure with alternating coarse and fine grains and finely dispersed intermetallic compounds Al were obtained. 11 Ce3 and CeZn 11 It has a good modification effect, effectively improving the strength of the alloy and enhancing its work hardening ability. It has a high uniform elongation and a moderate degradation rate, which can ensure the mechanical performance requirements and safety of cardiovascular stents.

[0043] Although Comparative Example 1 still exhibits high strength (400 MPa), its strength-ductility balance deteriorates. A possible reason is the excessively high Ce content, which leads to the formation of coarse, continuous brittle intermetallic compounds (such as Al). 11 Ce3 or CeZn 11 These particles accumulate at grain boundaries, acting as crack initiation sites and severely impairing plasticity (elongation drops to 17%).

[0044] In Comparative Example 2, due to the lack of rare earth element Ce, the alloy lost the crucial grain refinement and second-phase strengthening effects, resulting in a significant decrease in strength (335 MPa). The elongation (21%) was acceptable, mainly due to the solid solution strengthening of Mn and the bimodal structure, but the overall performance was poor.

[0045] The insufficient strengthening effect in Comparative Example 4 may be due to the fact that when the Al content is too low, the 0.12% Ce cannot completely form Al. 11 Ce3 may generate other Ce-rich phases or make the Ce metamorphism effect insufficient.

[0046] The elongation of Comparative Example 6 is not high, possibly because isothermal annealing is not conducive to the formation of an ideal bimodal structure, resulting in uneven grain size or poor control of recrystallization behavior, thereby impairing the material's ability to undergo uniform plastic deformation.

[0047] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0048] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A high-strength, high-toughness, biodegradable zinc alloy, characterized in that, It includes the following components by weight percentage: Mn 0.1~1%, Al 0.1~0.5%, Ce 0.01~0.12%, with the balance being Zn.

2. The high-strength, high-toughness, biodegradable zinc alloy as described in claim 1, characterized in that, It is composed of the following components by weight percentage: Mn 0.1~1%, Al 0.1~0.5%, Ce 0.01~0.12%, with the balance being Zn.

3. The high-strength, high-toughness, biodegradable zinc alloy as described in claim 1, characterized in that, It includes the following components by weight percentage: Mn 0.2~0.8%, Al 0.2~0.5%, Ce 0.05~0.12%, with the balance being Zn.

4. A method for preparing a high-strength, high-toughness, biodegradable zinc alloy as described in any one of claims 1-3, characterized in that, The zinc alloy ingot is homogenized, then hot-extruded, subjected to multiple drawing and annealing cycles, and finally aged to obtain a high-strength, tough, biodegradable zinc alloy.

5. The preparation method according to claim 4, characterized in that, The zinc alloy ingot is smelted at a temperature of 800~860℃ during preparation.

6. The preparation method according to claim 4, characterized in that, The homogenization process involves isostatic pressing under vacuum or inert gas protection at a temperature of 120-400°C; followed by water cooling.

7. The preparation method according to claim 4, characterized in that, The temperature of the hot extrusion deformation is 200~300℃, and the extrusion ratio is 15~35:

1.

8. The preparation method according to claim 4, characterized in that, Drawing is performed at room temperature with a drawing speed of 20-40 mm / s. The annealing temperature is 150-300℃ and the holding time is 60-120 min. As the number of drawing passes increases, the annealing temperature after each drawing pass gradually decreases. The number of alternating drawing and annealing processes is no less than 5.

9. The preparation method according to claim 4, characterized in that, The aging treatment temperature is 25~200 ℃, the holding time is 5~20 hours, and air cooling or water cooling is used.

10. The preparation method according to claim 4, characterized in that, It also includes surface modification treatment after aging treatment, and the surface modification treatment method is one or more of surface carburizing, sandblasting, and passivation.

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