A high-strength and high-elongation degradable zinc alloy, a preparation method and applications thereof

Abstract

The application belongs to the technical field of biomedical metal materials, and particularly relates to a high-strength and high-elongation degradable zinc alloy, a preparation method and application, which comprises the following components in percentage by weight: Cu 0.5-1.5%, Mg 0.01-0.05%, rare earth metal 0.01-0.2%, the rare earth metal is Y and Ce, the weight ratio of Y and Ce is 1:0.5-2, and the balance is Zn; the application simultaneously improves the strength, uniform elongation and elongation after fracture, and has good stability and consistency.

Description

Technical Field

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

[0002] Biodegradable metallic materials can undergo controlled degradation within the human body as tissues heal, eliminating the need for secondary surgery. This offers significant clinical advantages in orthopedics and cardiovascular interventional therapy, making them a core area of ​​research in medical implant materials. Zinc-based alloys, as the third generation of biodegradable medical metals following magnesium-based and iron-based alloys, have a standard electrode potential between that of magnesium and iron, theoretically exhibiting degradation behavior more closely matched to the human tissue healing cycle. Furthermore, zinc is an essential trace element for the human body and possesses excellent biocompatibility, making it an ideal candidate material for biodegradable medical implants.

[0003] However, existing biodegradable zinc alloys still face many challenges. First, zinc alloys have a hexagonal close-packed (HCP) crystal system with poor lattice symmetry, resulting in strong anisotropy and orientation dependence of single-crystal deformation during room temperature deformation, leading to poor plasticity. Second, pure zinc and most zinc alloys have low melting points and poor thermal stability, making them prone to natural aging, which leads to increased strength but significantly reduced plasticity. More importantly, many high-strength zinc alloys exhibit a significant "strain softening" effect, which may lead to dynamic recrystallization (DRX) during deformation, resulting in a decrease in dislocation density, severely insufficient work hardening capacity, and low uniform elongation. This can easily lead to uneven deformation or even sudden fracture failure of implants, severely limiting their clinical applications. For example, although the extruded high-strength Zn-0.45Li alloy has a tensile strength as high as 408 MPa, its uniform elongation is only 2.3%. Therefore, developing a biodegradable zinc alloy that combines high strength, high uniform elongation, and excellent work hardening capacity is a key materials science problem that urgently needs to be solved in the field of biomedical metallic materials.

[0004] Zn-Cu alloys, due to the limiting solid solubility of Cu in the Zn matrix (2.75 wt%), possess both excellent solid solution strengthening effects and biocompatibility, making them the mainstream system for biodegradable zinc alloys used in medicine. Application publication number CN 120989453A discloses an anti-aging, high-strength, and tough biodegradable zinc alloy rod, its preparation method, and its applications, comprising the following weight percentage components: Cu 1.5–2.0%, Mg 0.01–0.05%, with the balance being Zn. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high-strength and high-elongation biodegradable zinc alloy, its preparation method and application, which improves strength, uniform elongation and elongation after fracture, and has good stability and consistency.

[0006] This invention provides a high-strength, high-elongation biodegradable zinc alloy comprising the following components by weight percentage: Cu 0.5-1.5%, Mg 0.01-0.05%, rare earth metals 0.01-0.2%, wherein the rare earth metals are Y and Ce, the weight ratio of Y to Ce is 1:0.5-2, and the balance is Zn.

[0007] Preferably, it is composed of the following components by weight percentage: Cu 0.5~1.5%, Mg 0.01~0.05%, rare earth metals 0.01~0.2%, wherein the rare earth metals are Y and Ce, the weight ratio of Y to Ce is 1:0.5~2, and the balance is Zn.

[0008] Preferably, the weight content of Cu is 0.8%.

[0009] Preferably, the weight content of rare earth metals is 0.03~0.15%.

[0010] Preferably, the weight ratio of Y to Ce is 1:1.

[0011] Preferably, the total mass percentage of impurities in the biodegradable zinc alloy does not exceed 0.05%, and the mass percentage of a single impurity element is ≤0.02%.

[0012] This invention provides a method for preparing the high-strength, high-elongation biodegradable zinc alloy, comprising the following steps: subjecting a zinc alloy ingot to homogenization heat treatment, followed by multi-pass rotary forging to obtain the biodegradable zinc alloy.

[0013] Preferably, the method for preparing the zinc alloy ingot involves melting the components. The melting steps are as follows: heating to 520~550℃ under inert gas protection, holding for 3~5 minutes, then cooling to 480~500℃, then heating again to 550~570℃, and then casting.

[0014] Preferably, the homogenization heat treatment temperature is 280℃~300℃ and the time is 6~12h; the number of multi-pass rotary forging is more than 7 times (preferably 7-13 times).

[0015] The biodegradable zinc alloy obtained by this invention is in the form of a rod with a diameter of 5 mm.

[0016] This invention provides an application of the high-strength, high-elongation biodegradable zinc alloy described above, which is used to prepare biodegradable medical implants. The biodegradable medical implants include orthopedic implants, cardiovascular implants, and dental implants. The orthopedic implants include bone screws, bone plates, bone pins, and interbody fusion devices. The cardiovascular implants include vascular stents and heart valve occluders.

[0017] The beneficial effects of this invention are that trace amounts of Mg can be completely dissolved in the Zn matrix without the precipitation of coarse second phases, and it synergistically produces a solid solution strengthening effect with Cu; at the same time, it can reduce the stacking fault energy of the Zn matrix and promote the non-basal plane during plastic deformation.<c+a> Slip activation improves the alloy's ability to undergo uniform plastic deformation; in addition, the solid solution Mg can enhance the diffusion activation energy of the Zn matrix, increase the recrystallization temperature of the alloy, and suppress the performance degradation caused by room temperature static recrystallization.

[0018] Trace amounts of rare earth elements Y and Ce can form nanoscale intermetallic compound second phases with the Zn matrix, which are dispersed along the grain boundaries. Through the grain boundary pinning effect, they can suppress excessive dynamic recrystallization during plastic deformation, fundamentally solving the strain softening problem of the alloy and improving its work hardening ability. At the same time, they can work synergistically with twin-induced dynamic recrystallization (TDRX) and continuous dynamic recrystallization (CDRX) to precisely control the formation of a bimodal heterogeneous grain structure in the alloy, achieving a synergistic improvement in strength and uniform plasticity.

[0019] This invention preferably uses 0.8wt% Cu, supplemented with trace amounts of Mg and rare earth elements for microalloying. Through the synergistic effect of multiple mechanisms—solid solution strengthening, second-phase grain boundary pinning, and heterogeneous structure back stress strengthening—it fundamentally solves the core problems of strain softening and insufficient work hardening capacity in Zn-0.8Cu-based alloys. The resulting bars have an ultimate tensile strength ≥300MPa, uniform elongation ≥15%, and elongation after fracture ≥40%, achieving a breakthrough in the synergistic combination of ultra-high strength and high uniform plasticity, and overcoming the technical bottleneck of extremely low uniform elongation in existing high-strength zinc alloys.

[0020] The preparation method of this invention is simple, which greatly reduces the difficulty of process control in industrial production. The performance deviation between product batches is ≤3%, realizing the standardized preparation of medical zinc alloy raw materials and meeting the raw material consistency requirements for the large-scale production of medical implantable devices.

[0021] This invention employs a room-temperature, multi-pass, high-strain-rate rotary forging process with no intermediate annealing, resulting in energy savings of over 30% and production efficiency more than double compared to traditional hot working processes. High-frequency radial forging introduces high-density twins into the alloy. Through the synergistic effect of twin-induced dynamic recrystallization and continuous dynamic recrystallization, the alloy's bimodal heterogeneous grain structure is precisely controlled. The fine-grained region imparts high strength to the alloy through grain refinement and back stress strengthening, while the coarse-grained region provides sufficient slip systems and dislocation storage capacity, ensuring the alloy's uniform plastic deformation capability and effectively improving the plastic defects caused by insufficient slip systems in the close-packed hexagonal structure of zinc alloys.

[0022] This invention utilizes the synergistic solid solution and second-phase pinning effect of Cu, Mg, and rare earth elements to raise the recrystallization temperature of the alloy from near room temperature (for pure zinc) to over 200°C, effectively suppressing natural aging and static recrystallization during room temperature storage. The resulting rods, after being sealed and stored at room temperature for 6 months, exhibit tensile strength and plasticity fluctuations of ≤5%, with no significant performance degradation. This solves the technical problem of the rapid drop in plasticity of existing zinc alloys during room temperature storage, meeting the performance stability requirements for long-term storage, transportation, and clinical application of medical implant materials. Detailed Implementation

[0023] 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.

[0024] The testing standard for tensile strength and elongation is GB / T 228.1. 2010: Method for tensile testing of metallic materials at room temperature.

[0025] Example 1 This embodiment provides a Zn-0.8Cu-Mg-RE series zinc alloy bar, with the following chemical composition by weight percentage: Cu 0.8%, Mg 0.05%, Y 0.05%, Ce 0.05%, with the balance being Zn and unavoidable impurities, the total mass percentage of impurities ≤0.05%, and the mass percentage of a single impurity element ≤0.02%.

[0026] The preparation method includes the following steps: S1 Batching and Vacuum Melting: Accurately weigh pure Zn (99.99wt%), pure Cu (99.99wt%), pure Mg (99.99wt%), and Zn-RE master alloy (Zn-Y, Zn-Ce master alloy, RE mass fraction of 20%) according to the target chemical composition. Place them in a graphite crucible and put it into a vacuum induction melting furnace. Evacuate to ≤1×10⁻⁶. - After passing through ³Pa, high-purity argon gas is introduced as a protective atmosphere, and a two-step heating method is used for melting: first, the temperature is raised to 530℃ and held for 4 minutes until the raw material is completely melted; then the temperature is lowered to 480℃ and held for 2 minutes, and then the temperature is rapidly raised to 560℃. Electromagnetic stirring (frequency 1000Hz) is turned on and stirred evenly. The mixture is then quickly removed from the furnace and cast into a graphite mold preheated to 220℃. It is then allowed to cool naturally to room temperature to obtain a zinc alloy ingot. S2 Homogenization Heat Treatment: The zinc alloy ingot is placed in an argon-protected box-type heat treatment furnace and held at 280℃ for 12 hours for homogenization treatment to eliminate component segregation and casting internal stress of the ingot. After the treatment is completed, it is air-cooled to room temperature. S3 Room Temperature Multi-Pass High Strain Rate Rotary Forging: A homogenized zinc alloy ingot is subjected to multi-pass rotary forging to obtain an anti-aging, high-strength, tough, and biodegradable zinc alloy bar with a diameter of 5 mm. The number of rotary forging passes is 10.

[0027] Example 2 Example 2 differs from Example 1 in that its chemical composition is as follows: Cu 1.2%, Mg 0.01%, Y 0.05%, Ce 0.1%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0028] Example 3 Example 3 differs from Example 1 in that its chemical composition is as follows: Cu 0.5%, Mg 0.05%, Y 0.1%, Ce 0.05%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0029] Comparative Example 1 Compared with Example 1, Comparative Example 1 differs in its chemical composition as follows: Cu 0.8%, Mg 0.05%, Y 0.05%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0030] Comparative Example 2 Compared with Example 1, Comparative Example 2 differs in its chemical composition as follows: Cu 0.8%, Mg 0.05%, Y 0.1%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0031] Comparative Example 3 Compared with Example 1, Comparative Example 3 differs in its chemical composition as follows: Cu 0.8%, Mg 0.05%, Ce 0.05%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0032] Comparative Example 4 Compared with Example 1, Comparative Example 4 differs in its chemical composition as follows: Cu 0.8%, Mg 0.05%, Ce 0.1%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0033] Comparative Example 5 Compared with Example 1, Comparative Example 5 differs in its chemical composition as follows: Cu 0.8%, Mg 0.05%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0034] Comparative Example 6 Compared with Example 1, Comparative Example 6 differs in its chemical composition as follows: Cu 0.8%, Mg 0.05%, Y 0.2%, Ce 0.2%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0035] Comparative Example 7 Comparative Example 7 differs from Example 1 in its chemical composition as follows: Cu 0.8%, Mg 0.05%, Y 0.12%, Ce 0.04%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0036] Comparative Example 8 Compared with Example 1, Comparative Example 8 differs in its chemical composition as follows: Cu 0.8%, Mg 0.05%, Gd 0.05%, La 0.05%, with the balance being Zn and unavoidable impurities. Everything else is the same as in Example 1.

[0037] The performance of the test examples and comparative examples was tested, and the performance comparison table is shown in Table 1.

[0038] Table 1 Performance Comparison Table

[0039] This invention improves strength, uniform elongation, and elongation after fracture by microalloying Cu with trace amounts of Mg and rare earth elements Y and Ce, while also achieving good stability and consistency. This provides a mature technical solution for the standardized, large-scale production and clinical application of biodegradable zinc alloys for medical use.

[0040] 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.

[0041] 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-elongation biodegradable zinc alloy, characterized in that, It is composed of the following components by weight percentage: Cu 0.8%, Mg 0.01~0.05%, rare earth metals 0.01~0.2%, wherein the rare earth metals are Y and Ce, the weight ratio of Y and Ce is 1:1, and the balance is Zn.

2. The high-strength, high-elongation biodegradable zinc alloy as described in claim 1, characterized in that, The weight content of rare earth metals is 0.03~0.15%.

3. The high-strength, high-elongation biodegradable zinc alloy as described in claim 1 or 2, characterized in that, The total mass percentage of impurities in the biodegradable zinc alloy does not exceed 0.05%, and the mass percentage of a single impurity element is ≤0.02%.

4. A method for preparing a high-strength, high-elongation biodegradable zinc alloy as described in any one of claims 1-3, characterized in that, The process includes the following steps: homogenizing the zinc alloy ingot with heat treatment, followed by multi-pass rotary forging to obtain a biodegradable zinc alloy.

5. The preparation method according to claim 4, characterized in that, The method for preparing the zinc alloy ingot involves melting the components. The melting steps are as follows: heating to 520~550℃ under inert gas protection, holding for 3~5 minutes, then cooling to 480~500℃, then heating again to 550~570℃, and then casting.

6. The preparation method according to claim 4, characterized in that, The homogenization heat treatment temperature is 280℃~300℃, and the time is 6~12h; the number of multi-pass rotary forging is more than 7 times.

7. An application of a high-strength, high-elongation biodegradable zinc alloy as described in any one of claims 1-3, characterized in that, The biodegradable zinc alloy is used to manufacture biodegradable medical implants.

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