A high-toughness creep-resistant corrosion-resistant zinc alloy with a multi-stage gradient heterogeneous structure and a preparation method and application thereof

Abstract

This invention discloses a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure, its preparation method, and its applications, belonging to the field of zinc alloy material processing technology. The alloy's microstructure exhibits a three-layer gradient distribution from the inside out: the central main mechanical load-bearing region is composed of substructure grains, serving as a rigid framework to resist deformation; the intermediate grain boundary pinning and blocking regions are distributed with high-density necklace-like MnZn... 13 The second phase is used to lock grain boundary slip in situ and shield longitudinal pitting corrosion; the outer uniform corrosion-inducing zone is composed of recrystallized grains, used to induce uniform surface degradation. This invention utilizes a "die-bulk" gradient temperature control and unsteady-state variable-speed extrusion process, combined with pre-stretching aging treatment, to achieve an ultra-high tensile strength of 472.5-485.0 MPa while reducing the steady-state creep rate of the alloy to 6.0 × 10⁻⁶. ‑10 -9.0×10 ‑10 s ‑1 The scope was expanded, and the potential for localized pitting and perforation was eliminated.

Description

Technical Field

[0001] This invention relates to a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure, its preparation method, and its application, belonging to the field of zinc alloy material processing technology. Background Technology

[0002] Zinc (Zn) and its alloys, as a new generation of biodegradable metals, are considered the third generation of medical implant materials after stainless steel and titanium alloys due to their suitable degradation rate and excellent biocompatibility, showing great application potential in orthopedic internal fixation and cardiovascular interventional fields. However, a fundamental physical obstacle restricting its clinical application lies in the low melting point of zinc. From the perspective of metal physics, normal human body temperature is more than 40% of zinc's absolute melting point. This means that under physiological conditions, zinc alloys are essentially in a high-temperature creep region for a long time, with active atomic diffusion and extremely unstable grain boundaries. This inherent physical characteristic makes zinc alloy implants prone to irreversible creep deformation under continuous loads such as vascular rebound force or bone support force, becoming its biggest natural weakness as a load-bearing implant material.

[0003] However, existing technologies for improving the performance of zinc alloys generally face a triple contradiction: difficulty in simultaneously achieving strength, dimensional stability, and corrosion resistance. First, there is the problem of "strong creep inversion": zinc has a low melting point, placing it in the high-temperature creep range at room temperature and body temperature. Existing technologies pursuing ultra-high strength often introduce numerous grain boundaries through grain refinement, leading to a surge in creep slip channels and extremely poor dimensional stability. Implants are highly susceptible to radial shrinkage and collapse during long-term service. While existing technologies pursuing creep resistance can suppress creep through precipitates, their tensile strength is generally low due to limitations in the strengthening mechanism, making it difficult to meet the stringent high load-bearing requirements of thin-walled interventional devices. Second, there is the risk of brittle fracture due to pitting corrosion: traditional high-strength zinc alloys are highly susceptible to localized pitting corrosion in physiological environments due to uneven tissue potential. These deep-penetrating corrosion pits act like pre-existing cracks, inducing stress corrosion cracking under service stress, leading to catastrophic brittle fracture of the implant in the early stages of degradation. In summary, the industry urgently needs a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy material. Summary of the Invention

[0004] This invention provides a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure. The microstructure of the alloy exhibits a three-layer gradient distribution from the inside out. The central main mechanical load-bearing zone is located at the center of the cross-section and consists of fibrous substructure grains with an average width of 8-12 μm perpendicular to the extrusion direction. The grain boundaries are blurred, and the grains contain high-density dislocation walls. The intermediate grain boundary pinning and blocking zone is located between the core and the surface layer and consists of ultrafine grains with an average grain size of 0.3-0.6 μm. In this region, nano-sized MnZn... 13The second-phase particles are distributed in a high-density, continuous necklace-like pattern along the grain boundaries; the outermost uniform corrosion-induced zone is located in the outermost layer and consists of recrystallized grains with an average grain size of 1.5-2.5 μm.

[0005] Meanwhile, this invention provides a method for preparing a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure.

[0006] Meanwhile, this invention provides an application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure is disclosed. The cross-sectional microstructure of the alloy profile exhibits a non-uniform concentric three-layer ring-shaped distribution, consisting of a central substructural region, a middle high-density fine-grained ring region, and an outer relaxation region from the inside out. The grains in the central substructural region are fibrously distributed along the extrusion direction, with an average width of 8-12 μm, blurred grain boundaries, and high-density dislocation walls. The middle high-density fine-grained ring region forms a ring-shaped transition zone surrounding the central substructural region, composed of equiaxed ultrafine grains with an average size of 0.3-0.6 μm. In this region, nanoscale MnZn... 13 The second phase particles are distributed in a high-density, continuous necklace-like pattern along the grain boundaries; the outer relaxation region is located in the outermost layer and consists of recrystallized grains with an average grain size of 1.5-2.5 μm.

[0008] The chemical composition of the alloy, by mass percentage, is: Mn 0.42-0.45%, Mg 0.22-0.25%, with the balance being Zn and unavoidable impurities; wherein the mass ratio of Mn to Mg is strictly controlled between 1.8 and 1.91.

[0009] The present invention relates to a high-strength, high-toughness, creep-resistant, and corrosion-resistant Zn-Mn-Mg alloy with a multi-level gradient heterogeneous structure. The alloy possesses the following mechanical, creep-resistant, and corrosion-resistant properties: tensile strength of 472.5-485.0 MPa, elongation after fracture of 26.5%-29.0%; and a steady-state creep rate of 6.0 × 10⁻⁶ under constant tensile stress of 120 MPa at 25°C. -10 -9.0×10 -10 s -1 The average corrosion rate after immersion in simulated body fluid for 30 days was 0.025~0.045 mm / year, and the corrosion surface showed a uniform layered peeling pattern without local pitting corrosion pits with a depth exceeding 15 μm.

[0010] A method for preparing a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure includes the following steps: SO1 uses industrial-grade Zn, Mn, and Mg as raw materials. All raw materials are dried by forced-air drying at 150℃ for 6 hours before smelting.

[0011] SO2 is melted in a steel crucible, which is heated along with the furnace. Melting is carried out under a protective atmosphere. When heated to 400-420℃, Zn is added to the crucible, and the temperature is further increased to 580-600℃. After Zn is completely melted, Mn and Mg are added, and the temperature is further increased to 650-670℃. After the alloying elements are completely melted and mechanically stirred evenly, slag removal and refining are performed. The melt is poured into an iron mold preheated to 180-220℃, and the cooling rate is controlled. The melt is then air-cooled to room temperature to obtain an alloy ingot. S03, place the ingot in a heat treatment furnace, first stage annealing: heat to 310-330℃ and hold for 8-12 hours; S04 is cooled to 190-210℃ in the furnace and kept at that temperature for 12-16 hours. S05, the alloy processed from S04 is taken out and placed in a 0-4℃ ice-water mixture for cooling; S06 involves mechanically turning the alloy processed in S05 to remove a 1-2 mm thick surface layer and then processing the extruded billet. S07, heat the extrusion die and maintain it at 180-200℃, while preheating the alloy treated with S06 to 130-140℃ and holding it for 15-20 minutes, so that the die temperature is 40-70℃ higher than the billet temperature before extrusion begins. S08 involves subjecting the alloy treated with S07 to a non-steady-state variable-speed extrusion process: controlling the extrusion speed. v Over time t According to the law of sinusoids v = A sin( ωt )+ B It exhibits periodic fluctuations; among which: A The velocity amplitude, which ranges from 1 to 2 mm / s, is used to control the intensity of shear force fluctuations. B The reference extrusion speed, ranging from 1.5 to 3 mm / s, is used to control the overall forming efficiency. oh Angular frequency ( oh =2 π / T ,in T (for fluctuation cycles) S09, immediately after the profile is extruded from the die, the surface of the profile is forced to cool by air or water mist medium, so that the profile is cooled to below 50°C within 10 seconds. S10: Fix both ends of the cooled profile to the clamps of the stretching machine and load it at a stretching rate of 1-2 mm / min to produce a plastic elongation of 1.0%-2.0%. After unloading, place it in an environment of 80-100℃ for 4-8 hours of artificial aging treatment, and finally air cool it to room temperature.

[0012] Preferably, in SO1, the zinc ingot has a purity of 99.99 wt.% or higher; the manganese particles have a purity of 99.99 wt.% or higher; the magnesium particles have a purity of 99.99 wt.% or higher; and the particle size is 4-6 mm.

[0013] Preferably, in SO2, the protective atmosphere is a mixture of CO2 and FS6 in a volume ratio of 99:1.

[0014] Preferably, in S04, the average cooling rate during furnace cooling is controlled at 0.5-2.0℃ / min.

[0015] Preferably, in S05, the mass ratio of ice to water in the ice-water mixture is 1:(1-3), and the cooling medium is continuously stirred during the quenching process to ensure uniform cooling of the ingot.

[0016] Preferably, in S08, the extrusion ratio of the variable speed extrusion process is between 10:1 and 25:1; the extrusion speed is controlled. v The fluctuation range is 0.5-4.0 mm / s, and the fluctuation period is... T The duration is 2.0-10.0 seconds.

[0017] Preferably, in S10, during the pre-tension deformation aging, the initial strain rate of the tensile loading is 1.0 × 10⁻⁶. -3 s -1 Up to 5.0×10 -3 s -1 The temperature fluctuation during the artificial aging process is controlled within ±2℃.

[0018] The present invention relates to the application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure in the fields of rail transportation, machinery manufacturing, and biomedical implants (such as orthopedic implants and vascular stents).

[0019] Preferably, the present invention relates to the application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure in thin-walled load-bearing implant materials; the thin-walled load-bearing implant materials include, but are not limited to, cardiovascular and peripheral vascular interventional stents with a wall thickness of 50-150 μm, miniature orthopedic inner plates with a wall thickness of 0.5-1.5 mm, and surgical anastomosis clips with a wall thickness of 0.2-1.0 mm.

[0020] The beneficial effects achieved by this invention are as follows: (1) The alloy of the present invention exhibits a gradient distribution characteristic from the inside to the outside at the microscopic level, and each region plays a synergistic role for different failure modes: the coarse fibrous substructure grains and high-density dislocation walls retained in the central region constitute the main mechanical load-bearing unit resisting macroscopic deformation, ensuring the ultra-high strength of the alloy; in view of the creep failure problem caused by grain boundary slip that zinc alloys are prone to, the present invention utilizes the necklace-like MnZn precipitated at high density along the grain boundary in the middle region between the core and the surface layer. 13 Nanoparticles were used to construct a high-density grain boundary pinning network. This network effectively suppressed creep deformation at room temperature by increasing the resistance to grain boundary slip; simultaneously, this dense second-phase network also acted as a corrosion-blocking layer, forcing the corrosion path to deflect laterally; while the outermost layer, affected by extrusion heat, underwent stress relaxation and grain growth, effectively inducing the uniform nucleation of corrosion products. This design simultaneously achieves a structural-functional integration of mechanical strengthening, excellent dimensional stability, and pitting corrosion suppression.

[0021] (2) In the prior art, although grain refinement through large deformation can improve strength, the increase in grain boundary density significantly accelerates room temperature creep slip; while the precipitation of a second phase through alloying can suppress creep, it often leads to insufficient matrix strength. The present invention, through the above-mentioned gradient heterogeneous design, cleverly utilizes the central substructure to bear the load and uses the necklace-like second phase in the intermediate layer to lock the grain boundaries, successfully breaking the performance bottleneck of "strength-creep inversion". Under the premise of ensuring ultra-high strength, it eliminates the defect of conventional high-strength fine-grained zinc alloys that are prone to creep shrinkage.

[0022] (3) Based on the above mechanism, the alloy of this invention exhibits excellent comprehensive service performance. Experimental tests show that the tensile strength of this alloy is as high as 472.5-485.0 MPa, and the elongation after fracture remains above 26.5%; especially under the high constant tensile stress conditions of 120 MPa and 25℃, its steady-state creep rate is as low as 6.0 × 10⁻⁶. -10 -9.0×10 -10 s -1 It exhibits excellent dimensional stability; after immersion in simulated body fluid for 30 days, the average corrosion rate is 0.025-0.045 mm / year, and the corrosion surface shows a uniform layered peeling pattern without local pitting corrosion pits with a depth exceeding 15 μm, ensuring structural safety throughout the entire degradation cycle.

[0023] (4) The alloy of the present invention can adapt to complex deformation processes such as laser cutting and pressing and curling, and the device has low springback rate and good dimensional accuracy retention after molding, and has extremely high clinical translation value.

[0024] This invention discloses a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure, its preparation method, and its applications. The microstructure of the alloy exhibits a three-layer gradient distribution from the inside out: the central main mechanical load-bearing region is composed of substructure grains, serving as a rigid framework to resist deformation; the intermediate grain boundary pinning and blocking region contains high-density necklace-like MnZn... 13 The second phase is used to lock grain boundary slip in situ and shield longitudinal pitting corrosion; the outer uniform corrosion-inducing zone is composed of recrystallized grains, used to induce uniform surface degradation. This invention utilizes a "die-bulk" gradient temperature control and unsteady-state variable-speed extrusion process, combined with pre-stretching aging treatment, to achieve an ultra-high tensile strength of 472.5-485.0 MPa while reducing the steady-state creep rate of the alloy to 6.0 × 10⁻⁶. -10 -9.0×10 -10 s -1 The range was expanded, and the hidden dangers of local pitting corrosion and perforation were eliminated, perfectly solving the industry problem of "difficulty in achieving both high strength and dimensional stability" in medical zinc alloys. Attached Figure Description

[0025] Figure 1 This is the inverse pole figure (IPF) of the Zn-Mn-Mg alloy prepared in Example 1 of the present invention; the figure clearly shows the three-layer gradient isomorphic characteristics from the inside to the outside: the central region retains coarse fibrous substructure grains elongated along the extrusion direction; the middle region is an ultrafine equiaxed crystal ring formed by severe shearing; and the outer region is a coarse equiaxed grain that has undergone complete recrystallization. Figure 2 This is a scanning electron microscope (SEM) image of the Zn-Mn-Mg alloy prepared in Example 1 of this invention; the bright white particles indicated by the yellow arrows in the image are nano-sized MnZn. 13 The second phase; as shown by the red arrow in the figure, the second phase particles are distributed in a high-density continuous manner along the grain boundaries of the ultrafine crystals, forming a typical necklace-like feature; Figure 3 This is the EBSD inverse pole figure (IPF) of the cross-section of the zinc alloy profile prepared in Comparative Example 1. Due to the lack of a die-bulk temperature gradient during extrusion, the figure shows that the alloy exhibits uniformly distributed fine recrystallized grains and fails to form a coarse-centered substructure framework. Figure 4 This is the EBSD inverse pole figure (IPF) of the cross-section of the zinc alloy profile prepared in Comparative Example 2. Due to the lack of intense dynamic shearing action caused by pulse speed change during extrusion, the figure shows that the intermediate layer failed to form a high-density necklace-like second phase, and the precipitated phase is sparsely and unevenly distributed. Detailed Implementation

[0026] The following description, in conjunction with the accompanying drawings and embodiments of the present invention, will further clarify the objectives, technical solutions, and advantages of the present invention. The specific embodiments described are merely illustrative and are not intended to limit the scope of the invention. Example 1

[0027] A high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure, wherein the mass percentage of alloying elements in the zinc alloy meets the following requirements: Mn: 0.42%, Mg: 0.22%, and the balance is Zn.

[0028] A method for preparing a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure includes the following steps: S01 uses industrial-grade pure Zn (purity above 99.99%), industrial-grade pure Mn (purity above 99.99%), and industrial-grade pure Mg (purity above 99.99%) as raw materials. All raw materials are dried by forced-air drying at 150℃ for 6 hours before smelting.

[0029] SO2 is melted in a steel crucible, which is heated along with the furnace. The melting is carried out under a protective atmosphere (a mixture of CO2 and FS6 in a volume ratio of 99:1). When heated to 400°C, Zn is added to the crucible, and the temperature is further increased to 580°C. After the Zn is completely melted, Mn and Mg are added, and the temperature is further increased to 650°C. After the alloying elements are completely melted and mechanically stirred evenly, slag removal and refining are performed. The melt is then poured into an iron mold preheated to 200°C, and the cooling rate is controlled. The melt is then air-cooled to room temperature to obtain an alloy ingot. S03, place the ingot in a heat treatment furnace and perform the first stage of annealing: heat to 320℃ and hold for 10 hours; S04 is cooled to 200℃ in the furnace, with the average cooling rate controlled at 1.0℃ / min, and then kept at that temperature for 14 hours. S05: The alloy processed by S04 is taken out and placed into a 0℃ ice-water mixture for cooling. The mass ratio of ice to water in the ice-water mixture is 1:1. The cooling medium is continuously stirred during the quenching process to ensure uniform cooling of the ingot. S06, the alloy processed by S05 is mechanically turned to remove a 2mm thick surface layer and is processed into an extruded billet with a diameter of 58mm. S07, heat the extrusion die and maintain it at 195°C, while preheating the alloy treated with S06 to 135°C and holding it for 20 minutes, so that the die temperature is 60°C higher than the billet temperature before extrusion begins. S08 involves subjecting the alloy treated with S07 to a non-steady-state variable-speed extrusion process: controlling the extrusion speed. v Over time t According to the law of sinusoids v =A sin( ωt )+ B It exhibits periodic fluctuations; among which: A The velocity amplitude is used to control the fluctuation intensity of the shear force. B The reference extrusion speed, ranging from 1.5 to 3 mm / s, is used to control the overall forming efficiency. oh Angular frequency ( oh =2 π / T ,in T (This refers to a fluctuating cycle) non-steady-state variable speed extrusion process with an extrusion ratio of 16:1. A baseline extrusion speed is set. B The velocity amplitude is 2.25 mm / s. A The extrusion speed is 1.75 mm / s. v It exhibits periodic continuous fluctuations between 0.5 mm / s and 4.0 mm / s, with a fluctuation period of... T It lasts for 5 seconds; S09, immediately after the profile is extruded from the die, high-pressure water mist is used to force-cool the profile surface, so that the profile temperature drops to below 50°C within 10 seconds; S10: After cooling, the two ends of the profile are fixed to the clamps of a stretching machine. A tensile load is applied at a rate of 1 mm / min, resulting in a 1.5% plastic elongation. After unloading, the profile is placed in a 90°C environment for 6 hours of artificial aging treatment, and finally air-cooled to room temperature. In the pre-stretch deformation aging, the initial strain rate of the tensile load is 3.0 × 10⁻⁶. -3 s -1 The temperature fluctuation during the artificial aging process is controlled within ±2℃.

[0030] This embodiment describes the application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure in fields such as rail transportation, machinery manufacturing, and biomedical implants (e.g., orthopedic implants, vascular stents).

[0031] This embodiment describes the application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure in thin-walled load-bearing implant materials; the thin-walled load-bearing implant materials include, but are not limited to, cardiovascular and peripheral vascular interventional stents with a wall thickness of 100 μm, miniature orthopedic inner plates with a wall thickness of 1.0 mm, and surgical anastomosis clips with a wall thickness of 0.5 mm.

[0032] This embodiment yields a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure. The cross-sectional microstructure of the alloy profile exhibits a non-uniform concentric three-layer ring-shaped distribution, consisting of a central substructural region, a middle high-density fine-grained ring region, and an outer relaxation region from the inside out. The grains in the central substructural region are fibrously distributed along the extrusion direction, with an average width of approximately 10 μm, blurred grain boundaries, and high-density dislocation walls. The middle high-density fine-grained ring region forms a ring-shaped transition zone surrounding the central substructural region, composed of equiaxed ultrafine grains with an average size of approximately 0.5 μm. In this region, nanoscale MnZn... 13 The second phase particles are distributed in a high-density, continuous necklace-like pattern along the grain boundaries; the outer relaxation region is located in the outermost layer and consists of recrystallized grains with an average grain size of about 2.0 μm.

[0033] Figure 1 The three-layer gradient heterogeneity of this embodiment is clearly shown from the inside out: the central region retains coarse fibrous substructure grains that are elongated along the extrusion direction; the middle region is an ultrafine equiaxed crystal ring formed by severe shearing; and the outer region is a coarse equiaxed grain that has undergone complete recrystallization. Figure 2 The bright white particles indicated by the yellow arrow are nano-sized MnZn. 13 The second phase; as shown by the red arrow in the figure, the second phase particles are distributed in a high-density continuous pattern along the grain boundaries of the ultrafine crystals, forming a typical necklace-like feature. Example 2

[0034] A high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure, wherein the mass percentage of alloying elements in the zinc alloy meets the following requirements: Mn: 0.44%, Mg: 0.23%, with the balance being Zn.

[0035] A method for preparing a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure includes the following steps: S01 uses industrial-grade pure Zn (purity above 99.99%), industrial-grade pure Mn (purity above 99.99%), and industrial-grade pure Mg (purity above 99.99%) as raw materials. All raw materials are dried by forced-air drying at 150℃ for 6 hours before smelting.

[0036] SO2 is melted in a steel crucible, which is heated along with the furnace. The melting is carried out under a protective atmosphere (a mixture of CO2 and FS6 in a volume ratio of 99:1). When heated to 410°C, Zn is added to the crucible, and the temperature is further increased to 590°C. After the Zn is completely melted, Mn and Mg are added, and the temperature is further increased to 660°C. After the alloying elements are completely melted and mechanically stirred evenly, slag removal and refining are performed. The melt is then poured into an iron mold preheated to 180°C, and the cooling rate is controlled. The melt is then air-cooled to room temperature to obtain an alloy ingot. S03, place the ingot in a heat treatment furnace, first stage annealing: heat to 310℃ and hold for 12 hours; S04 is cooled to 190℃ in the furnace, with the average cooling rate controlled at 0.5℃ / min, and then kept at that temperature for 16 hours. S05: The alloy processed by S04 is taken out and placed in a 2°C ice-water mixture for cooling. The mass ratio of ice to water in the ice-water mixture is 1:2. The cooling medium is continuously stirred during the quenching process to ensure uniform cooling of the ingot. S06, the alloy processed by S05 is mechanically turned to remove a 1mm thick surface layer and is processed into an extruded billet with a diameter of 58mm. S07, heat the extrusion die and maintain it at 180°C, while preheating the alloy treated with S06 to 140°C and holding it for 15 minutes, so that the die temperature is 40°C higher than the billet temperature before extrusion begins. S08 involves subjecting the alloy treated with S07 to a non-steady-state variable-speed extrusion process: controlling the extrusion speed. v Over time t According to the law of sinusoids v = A sin( ωt )+ B It exhibits periodic fluctuations; among which: A The velocity amplitude is used to control the fluctuation intensity of the shear force. B The reference extrusion speed, ranging from 1.5 to 3 mm / s, is used to control the overall forming efficiency. oh Angular frequency ( oh =2 π / T ,in T (For fluctuation period); non-steady-state variable speed extrusion process, extrusion ratio 25:1. Set the reference extrusion speed. B The velocity amplitude is 3 mm / s. A The fluctuation rate is 2 mm / s, and the period is... T It lasts for 10 seconds; S09, immediately after the profile is extruded from the die, high-pressure water mist is used to force-cool the profile surface, so that the profile temperature drops to below 50°C within 10 seconds; S10, after cooling, the two ends of the profile are fixed to the clamps of a stretching machine, and a tensile load is applied at a rate of 1.5 mm / min to induce a plastic elongation of 1.0%. After unloading, the profile is placed in an environment of 80°C for 8 hours of artificial aging treatment, and finally air-cooled to room temperature. In the pre-stretch deformation aging, the initial strain rate of the tensile load is 1.0 × 10⁻⁶. -3 s -1 The temperature fluctuation during the artificial aging process is controlled within ±2℃.

[0037] This embodiment describes the application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure in fields such as rail transportation, machinery manufacturing, and biomedical implants (e.g., orthopedic implants, vascular stents).

[0038] This embodiment describes the application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure in thin-walled load-bearing implant materials; the thin-walled load-bearing implant materials include, but are not limited to, cardiovascular and peripheral vascular interventional stents with a wall thickness of 50 μm, miniature orthopedic inner plates with a wall thickness of 0.5 mm, and surgical anastomosis clips with a wall thickness of 0.2 mm.

[0039] This embodiment yields a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure. The cross-sectional microstructure of the alloy profile exhibits a non-uniform concentric three-layer ring-shaped distribution, consisting of a central substructure region, a middle high-density fine-grained ring region, and an outer relaxation region, from the inside out. The grains in the central substructure region are fibrously distributed along the extrusion direction, with an average width of approximately 8 μm, blurred grain boundaries, and high-density dislocation walls. The middle high-density fine-grained ring region forms a ring-shaped transition zone surrounding the central substructure region, composed of equiaxed ultrafine grains with an average size of approximately 0.3 μm. In this region, nanoscale MnZn... 13 The second phase particles are distributed in a high-density, continuous necklace-like pattern along the grain boundaries; the outer relaxation region is located in the outermost layer and consists of recrystallized grains with an average grain size of about 1.5 μm. Example 3

[0040] A high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure, wherein the mass percentage of alloying elements in the zinc alloy meets the following requirements: Mn: 0.45%, Mg: 0.25%, and the balance is Zn.

[0041] A method for preparing a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure includes the following steps: S01 uses industrial-grade pure Zn (purity above 99.99%), industrial-grade pure Mn (purity above 99.99%), and industrial-grade pure Mg (purity above 99.99%) as raw materials. All raw materials are dried by forced-air drying at 150℃ for 6 hours before smelting.

[0042] SO2 is melted in a steel crucible, which is heated along with the furnace. The melting is carried out under a protective atmosphere (a mixture of CO2 and FS6 in a volume ratio of 99:1). When heated to 420°C, Zn is added to the crucible, and the temperature is further increased to 600°C. After the Zn is completely melted, Mn and Mg are added, and the temperature is further increased to 670°C. After the alloying elements are completely melted and mechanically stirred evenly, slag removal and refining are performed. The melt is poured into an iron mold preheated to 220°C, and the cooling rate is controlled. The melt is then air-cooled to room temperature to obtain an alloy ingot. S03, place the ingot in a heat treatment furnace and perform the first stage of annealing: heat to 330℃ and hold for 8 hours; S04 is cooled to 210℃ in the furnace, with the average cooling rate controlled at 2.0℃ / min, and then kept at that temperature for 12 hours. S05: The alloy processed by S04 is taken out and placed in a 4°C ice-water mixture for cooling. The mass ratio of ice to water in the ice-water mixture is 1:3. The cooling medium is continuously stirred during the quenching process to ensure uniform cooling of the ingot. S06, the alloy processed by S05 is mechanically turned to remove a 1.5mm thick surface layer and processed into an extruded billet with a diameter of 58mm; S07, heat the extrusion die and maintain it at 200°C, while preheating the alloy treated with S06 to 130°C and holding it for 18 minutes, so that the die temperature is 70°C higher than the billet temperature before extrusion begins. S08 involves subjecting the alloy treated with S07 to a non-steady-state variable-speed extrusion process: controlling the extrusion speed. v Over time t According to the law of sinusoids v = A sin( ωt )+ B It exhibits periodic fluctuations; among which: A The velocity amplitude is used to control the fluctuation intensity of the shear force. B The reference extrusion speed, ranging from 1.5 to 3 mm / s, is used to control the overall forming efficiency. oh Angular frequency ( oh =2 π / T ,in T (For fluctuation period); non-steady-state variable speed extrusion process, extrusion ratio 10:1. Set the reference extrusion speed. B The velocity amplitude is 1.5 mm / s. A The fluctuation period is 1 mm / s. T It takes 2 seconds; S09, immediately after the profile is extruded from the die, high-pressure water mist is used to force-cool the profile surface, so that the profile temperature drops to below 50°C within 10 seconds; S10, after cooling, the two ends of the profile are fixed to the clamps of a stretching machine, and a tensile load is applied at a rate of 2 mm / min to induce a plastic elongation of 2.0%. After unloading, the profile is placed in an environment of 100°C for 4 hours for artificial aging treatment, and finally air-cooled to room temperature. In the pre-stretch deformation aging, the initial strain rate of the tensile load is 5.0 × 10⁻⁶. -3 s -1 The temperature fluctuation during the artificial aging process is controlled within ±2℃.

[0043] This embodiment describes the application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure in fields such as rail transportation, machinery manufacturing, and biomedical implants (e.g., orthopedic implants, vascular stents).

[0044] This embodiment describes the application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure in thin-walled load-bearing implant materials; the thin-walled load-bearing implant materials include, but are not limited to, cardiovascular and peripheral vascular interventional stents with a wall thickness of 150 μm, miniature orthopedic inner plates with a wall thickness of 1.5 mm, and surgical anastomosis clips with a wall thickness of 1.0 mm.

[0045] This embodiment yields a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure. The cross-sectional microstructure of the alloy profile exhibits a non-uniform concentric three-layer ring-shaped distribution, consisting of a central substructural region, a middle high-density fine-grained ring region, and an outer relaxation region from the inside out. The grains in the central substructural region are fibrously distributed along the extrusion direction, with an average width of approximately 12 μm, blurred grain boundaries, and high-density dislocation walls. The middle high-density fine-grained ring region forms a ring-shaped transition zone surrounding the central substructural region, composed of equiaxed ultrafine grains with an average size of approximately 0.6 μm. In this region, nanoscale MnZn... 13 The second phase particles are distributed in a high-density, continuous necklace-like pattern along the grain boundaries; the outer relaxation region is located in the outermost layer and consists of recrystallized grains with an average grain size of about 2.5 μm.

[0046] Comparative Example 1

[0047] This comparative example maintains the same composition and subsequent treatment as Example 1, with the only difference being step S07: heating the mold and the blank to 180°C simultaneously and holding at that temperature (without temperature difference).

[0048] like Figure 3 As shown, the zinc alloy prepared in this comparative example lacks a temperature gradient, resulting in a microstructure without significant three-layer differences, exhibiting a relatively uniform fine-grained structure (average grain size approximately 3 μm). It lacks the support of a central coarse substructure framework. The alloy has a tensile strength of 395.8 MPa, an elongation of 32.3%, and a steady-state creep rate of 8.5 × 10⁻⁶. -8 s -1The corrosion rate is 0.122 mm / y.

[0049] Comparative Example 2

[0050] This comparative example maintains the same composition and temperature gradient as Example 1, with the only difference being step S08: the extrusion speed is kept constant at 2.0 mm / s (without pulse fluctuations).

[0051] like Figure 4 As shown, the zinc alloy prepared in this comparative example lacked the intense shearing and dynamic precipitation effects induced by pulsed acceleration, resulting in the failure to form a high-density "necklace-like" second phase in the intermediate layer, and a weak grain boundary pinning effect. The alloy exhibited a tensile strength of 410.5 MPa, an elongation of 30.2%, and a steady-state creep rate of 2.3 × 10⁻⁶ MPa. -7 s -1 The corrosion rate is 0.150 mm / y.

[0052] To compare the room temperature tensile mechanical properties of the various embodiments and comparative examples, room temperature tensile tests were performed on each alloy according to the national standard GB / T 228.1—2021, and their properties are summarized in Table 1 below.

[0053] Table 1 Mechanical Properties

[0054] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0055] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure, characterized in that: The cross-sectional microstructure of the alloy profile exhibits a non-uniform concentric three-layer ring distribution, consisting of a central substructure region, a middle high-density fine-grained ring region, and an outer relaxation region from the inside out. The grains in the central substructure region are distributed in a fibrous manner along the extrusion direction, with an average width of 8-12 μm. The grain boundaries are blurred and contain high-density dislocation walls. The central, highly dense, fine-grained ring region forms a ring-shaped transition zone surrounding the central substructure region. It consists of equiaxed ultrafine grains with an average size of 0.3-0.6 μm. Within this region, nanoscale MnZn... 13 The second-phase particles are distributed in a necklace-like pattern along the grain boundaries; The outer relaxation region consists of recrystallized grains with an average grain size of 1.5-2.5 μm; The chemical composition of the alloy, by mass percentage, is: Mn 0.42-0.45%, Mg 0.22-0.25%, with the balance being Zn and unavoidable impurities.

2. The high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure according to claim 1, characterized in that: The mass ratio of Mn to Mg was controlled between 1.8 and 1.

91.

3. The high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure according to claim 1, characterized in that: The alloy possesses the following mechanical, creep resistance, and corrosion resistance properties: tensile strength of 472.5-485.0 MPa, elongation after fracture of 26.5%-29.0%; and steady-state creep rate of 6.0 × 10⁻⁶ under constant tensile stress of 120 MPa at 25℃. -10 -9.0×10 -10 s -1 The average corrosion rate after immersion in simulated body fluid for 30 days was 0.025~0.045 mm / year, and the corrosion surface showed a uniform layered peeling pattern without local pitting corrosion pits with a depth exceeding 15 μm.

4. A method for preparing a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterostructure according to any one of claims 1-3, characterized in that: Includes the following steps: S01 uses industrial-grade Zn, industrial-grade Mn, and industrial-grade Mg as raw materials; all raw materials are dried before smelting. S02, the crucible is heated with the furnace and the melting is carried out under a protective atmosphere; when heated to 400-420℃, Zn is added to the crucible and heated to 580-600℃. After Zn is completely melted, Mn and Mg are added and heated to 650-670℃. After the alloying elements are completely melted and stirred evenly, slag removal and refining are carried out. The melt is poured into a mold preheated to 180-220℃ and air-cooled to room temperature to obtain an alloy ingot. S03, place the alloy ingot in a heat treatment furnace, first stage annealing: heat to 310-330℃ and hold for 8-12 hours; S04 is cooled to 190-210℃ in the furnace and kept at that temperature for 12-16 hours. S05, the alloy processed from S04 is taken out and placed in a 0-4℃ ice-water mixture for cooling; S06 involves mechanically turning the alloy processed in S05 to remove a 1-2 mm thick surface layer and then processing the extruded billet. S07, heat the extrusion die and maintain it at 180-200℃, while preheating the alloy treated with S06 to 130-140℃ and holding it for 15-20 minutes, so that the die temperature is 40-70℃ higher than the billet temperature before extrusion begins. S08 involves subjecting the alloy treated with S07 to a non-steady-state variable-speed extrusion process: controlling the extrusion speed. v Over time t According to the law of sinusoids v = A sin( ωt )+ B It exhibits periodic fluctuations; among which: A The velocity amplitude ranges from 1 to 2 mm / s; B The reference extrusion speed ranges from 1.5 to 3 mm / s. ω Angular frequency, ω =2 π / T ,in T The fluctuation period is 2.0-10.0s; S09, immediately after the profile is extruded from the die, the surface of the profile is forced to cool by air or water mist medium, so that the profile is cooled to below 50°C within 10 seconds. S10: Fix both ends of the cooled profile to the clamps of the stretching machine and load it at a stretching rate of 1-2 mm / min to produce a plastic elongation of 1.0%-2.0%. After unloading, place it in an environment of 80-100℃ for 4-8 hours of artificial aging treatment, and finally air cool it to room temperature.

5. The preparation method according to claim 4, characterized in that: In SO2, the protective atmosphere is a mixture of CO2 and FS6 in a volume ratio of 99:1; the crucible is a steel crucible; and the mold is an iron mold.

6. The preparation method according to claim 4, characterized in that: In S04, the average cooling rate during furnace cooling is controlled at 0.5-2.0℃ / min.

7. The preparation method according to claim 4, characterized in that: In S08, the extrusion ratio of the non-steady-state variable speed extrusion process is between 10:1 and 25:1; the extrusion speed is controlled. v The fluctuation range is 0.5-4.0 mm / s; In S10, during the pre-tension deformation aging, the initial strain rate of the tensile loading is 1.0 × 10⁻⁶. -3 s -1 Up to 5.0×10 -3 s -1 Temperature fluctuations during artificial aging are controlled within ±2℃.

8. The application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure according to any one of claims 1-3 in rail transit, machinery manufacturing, and biomedical implants, characterized in that: Biomedical implants include orthopedic implants and vascular stents.

9. The application of a high-strength, high-toughness, creep-resistant, and corrosion-resistant zinc alloy with a multi-level gradient heterogeneous structure according to any one of claims 1-3 in thin-walled load-bearing implant materials, characterized in that: Thin-walled load-bearing implant materials include cardiovascular and peripheral vascular interventional stents with a wall thickness of 50-150 μm, miniature orthopedic inner plates with a wall thickness of 0.5-1.5 mm, and surgical anastomosis clips with a wall thickness of 0.2-1.0 mm.

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