Superfine magnesium alloy wire as well as preparation method and application thereof

Abstract

The invention relates to a superfine magnesium alloy wire and a preparation method and application thereof.The preparation method comprises the following steps that S1, smelting is conducted, specifically, magnesium alloy raw materials are mixed and heated, and an alloy ingot is prepared; s2, extrusion is conducted, specifically, the alloy cast ingot is subjected to hot-pressing extrusion, and a wire rod with the diameter being 10-15 mm is obtained; s3, rotary forging is conducted, specifically, rotary forging machining is conducted on the wire rod N times, N is a positive integer larger than or equal to 3, and a thick wire is obtained; and S4, wire drawing is conducted, specifically, the thick wire is subjected to multi-pass continuous reducing drawing, annealing is conducted before each time of drawing, the single-pass reducing rate is controlled to be 10%-20% till the diameter is smaller than or equal to 0.6 mm, fine drawing is conducted, the single-pass reducing rate is controlled to be smaller than or equal to 5% till the diameter is 0.2-0.4 mm, surface polishing is conducted, and the superfine magnesium alloy wire is obtained. According to the method, the tensile strength of the material is improved, the surface smoothness meets the medical-grade requirement, collaborative optimization of the mechanical property and the microstructure of the obtained superfine magnesium alloy wire is achieved, and the superfine magnesium alloy wire is completely matched with use scenes such as anastomosis nails and intravascular stents.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloy wire processing, in particular to an ultrafine magnesium alloy wire and a preparation method and application thereof. Background Art

[0002] Magnesium alloys, due to their unique biodegradability and mechanical properties, hold great potential for application in the biomedical field. Furthermore, magnesium alloys have a density similar to that of human bone, and the magnesium ions produced by their degradation are essential minerals that promote bone and soft tissue healing. Therefore, they are considered a promising material for orthopedic implants, staples, and other implants such as cardiovascular stents. However, the diameter of the magnesium wire used in these applications is relatively small, and traditional magnesium alloy wire drawing processes (hot and cold drawing) face numerous challenges in producing ultrafine wires. Wires produced by traditional magnesium alloy wire drawing processes typically have diameters exceeding 1 mm. Producing magnesium alloys with diameters below 1 mm is prone to wire breakage, surface roughness, and numerous defects.

[0003] Patent application CN110193525A discloses a method for rapidly preparing magnesium alloy fine-grained wire based on a drawing process, which is completed in the following steps: Step 1, hot-extrude a magnesium alloy round rod ingot with a diameter of more than 30 mm into a rod with a diameter of φ of 6 mm to 10 mm, and then anneal; Step 2, then perform 3 to 5 hot drawing passes, and immediately water-cool to room temperature; Step 3, then perform 3 to 5 continuous cold drawing passes, anneal and air-cool to room temperature; Step 4, repeat steps 2 to 3 until the diameter φ is 1.0 mm to 1.5 mm. This method solves the problem of poor plastic deformation ability of magnesium alloy at room temperature by alternating high-temperature hot drawing and room temperature cold drawing, combined with multiple cold drawing passes and annealing, and successfully prepares high-efficiency, low-energy magnesium alloy fine grains and ultrafine wires. However, the tensile strength of the ultrafine wire obtained by the above method is about 80N, which cannot meet the application requirements of scenarios with higher strength.

[0004] The low strength and insufficient toughness of existing magnesium alloy wires are closely related to their crystal structure and the microstructural evolution during processing. Magnesium alloys have a close-packed hexagonal structure, and at room temperature, only the basal slip system can be activated. The critical shear stress of non-basal slip systems is much higher than that of the basal slip system. This anisotropy makes it difficult to achieve coordination of multiple slip systems during plastic deformation, and easily leads to stress concentration at grain boundaries or twin boundaries, which in turn triggers crack propagation.

[0005] From the perspective of precipitation strengthening mechanisms, while the β' phase formed during aging treatment of magnesium alloys can improve wire strength by hindering dislocation motion, the interfacial bonding characteristics of the precipitate with the matrix have a decisive influence on its strengthening effect. Research has shown that when basal plane dislocations shear the precipitate, local shear bands may form, leading to softening rather than strengthening. Furthermore, if the precipitate size distribution is uneven or the volume fraction is insufficient, it is difficult to effectively pin dislocations, which also plays a significant role in limiting the strength improvement.

[0006] In conventional drawing processes, magnesium alloys tend to form coarse grains during dynamic recrystallization, and brittle secondary phases tend to accumulate at grain boundaries. These brittle phases not only fail to contribute to strengthening, but can actually become crack sources. Furthermore, the close-packed hexagonal structure of magnesium alloys results in poor room-temperature plasticity, necessitating multiple, small deformation passes during drawing. Repeated work hardening further exacerbates dislocation entanglement and reduces the material's toughness.

[0007] The selection and ratio of alloying elements are also key constraints. While the addition of rare earth elements can improve high-temperature performance through solid solution strengthening and the formation of thermally stable phases (such as intermetallic compounds containing Gd and Y), excessive rare earth elements can reduce matrix ductility. For example, excessively high concentrations of dissolved atoms in Mg-Gd-Y-Zr alloys can inhibit twin nucleation, resulting in a single deformation mechanism. Furthermore, the high chemical activity of magnesium alloys makes them susceptible to surface oxidation during processing. The resulting oxide film breaks down during subsequent deformation, forming microcracks and further deteriorating mechanical properties. Furthermore, the addition of rare earth elements makes it difficult to assess the biosafety of magnesium alloys, increasing safety risks during human implantation and hindering their commercial application. These factors combine to make it difficult to achieve an ideal balance between strength and toughness in existing magnesium alloy wires, particularly those used in medical applications.

[0008] Refining the grain structure is one of the potential effective ways to achieve a synergistic improvement in both high strength and high plasticity in magnesium alloy wire. Research has shown that when the grain size is refined to the submicron level, the grain boundary density increases significantly. This not only improves strength through the Hall-Petch effect, but also induces shear texture, increases the basal slip Schmidt factor, and thus coordinates the initiation of multiple slip systems, improving plastic deformation capacity.

[0009] Among the various methods for achieving grain refinement of magnesium alloy wire, rotary forging technology has significant advantages due to its unique multi-directional compressive stress state and pulse loading characteristics. Figure 1The rotary swaging process is a plastic forming technology that applies high-frequency pulse loads to the metal blank by rotating the hammer head. Its core lies in the use of multi-directional compressive stress and multi-pass progressive deformation to achieve grain refinement and mechanical property improvement. Several dies are continuously processed on the workpiece in rapid succession. During this period, the material begins to plastically deform and is formed with high precision. When using rotary swaging to process magnesium alloy wire, the preheated bar blank is usually fed into the rotary swaging machine. By gradually replacing the rotary swaging dies with decreasing apertures, multiple compressions are performed at different feed speeds to induce dynamic recrystallization and dispersion strengthening phase precipitation. Figure 2 This is a schematic diagram of magnesium alloy disc forging into thick wire. Thick wire with a diameter of about 10 mm can be obtained through the forging process.

[0010] However, although rotary swaging technology can achieve grain refinement of magnesium alloy wires, in order to obtain high-strength ultrafine magnesium alloy wires, rotary swaging of thick wires with a diameter of less than 10 mm is prone to wire breakage, making continuous industrial production impossible. Summary of the Invention

[0011] The purpose of the present invention is to overcome the problem of wire breakage that occurs in the preparation process of existing ultrafine magnesium alloy wires, and to provide an ultrafine magnesium alloy wire and its preparation method and application. By optimizing the rotary swaging process, the problem of wire breakage in the process of processing thick wires (diameter 10-15 mm) into thin wires (diameter 1.0-1.5 mm) and the problem of wire breakage in the process of further fine drawing the thin wires into ultrafine wires (diameter 0.2-0.4 mm) are solved.

[0012] The specific plan is as follows: A method for preparing an ultrafine magnesium alloy wire comprises the following steps: S1 smelting: mixing and heating the magnesium alloy raw materials to prepare alloy ingots; S2 extrusion: hot pressing and extruding the alloy ingot to obtain a disk with a diameter of 10-15 mm; S3 rotary swaging: performing rotary swaging on the coil N times, where N is a positive integer greater than or equal to 3, to obtain a thick wire; wherein the temperature is controlled at 20-250° C., the feeding speed is 1-5 m / min, and the diameter reduction per pass is 0.1-3 mm; S4 wire drawing: The thick wire is subjected to multiple continuous diameter reduction drawing, annealing is performed before each drawing, and then drawing is performed. During drawing, the single-pass diameter reduction rate is controlled to be 10%-20%, until the diameter is less than or equal to 0.6 mm, and fine drawing is performed, and the single-pass diameter reduction rate is controlled to be ≤5% until the diameter is 0.2-0.4 mm, and the surface is polished to obtain an ultrafine magnesium alloy wire.

[0013] Furthermore, in S1 smelting, the heating adopts an anaerobic environment, preferably an argon atmosphere, and the temperature is first raised to above 700°C for refining, and then cast at 700°C±20°C to obtain the alloy ingot, which contains the following elements, in terms of mass percentage: Zn: 1-5%, Ca: 0.01-1.5%, Mn: 0.01-0.5%, and the balance is Mg and unavoidable impurity elements.

[0014] Furthermore, in S2 extrusion, the hot pressing extrusion includes first keeping the alloy ingot at 350°C±20°C for 3-6 hours, and then extruding it at 300-400°C and an extrusion ratio of 50-80.

[0015] Furthermore, in S3 rotary forging, three rotary forgings are performed by combining temperature reduction and feed speed reduction, specifically including: In the first rotary forging, the rotary forging temperature is controlled at 150℃±20℃, the diameter is reduced by 1~1.2mm per pass, the total diameter reduction is at a feeding speed of 4.5~5m / min, and the final wire forming diameter is 7-9mm; The second rotary forging is based on the first rotary forging, the rotary forging temperature is changed to 80℃±20℃, the diameter is reduced by 0.4~0.5mm per pass, the feeding speed is reduced to 3.5~4m / min, and the final wire forming diameter is 3-4mm; The third rotary forging is based on the second rotary forging. The rotary forging temperature is changed to room temperature, the diameter is reduced by 0.2~0.3mm per pass, the feeding speed is reduced to 2~2.5m / min, and the final wire forming diameter is 1.0-1.5mm.

[0016] Furthermore, in S3 rotary forging, three rotary forgings are performed by combining temperature reduction and constant feed speed, specifically including: In the first rotary forging, the rotary forging temperature is controlled at 200℃±20℃, the diameter is reduced by 2~2.5mm per pass, the total diameter reduction rate is 4~5m / min, and the final wire forming diameter is 7-9mm; The second rotary forging is based on the first rotary forging, and the rotary forging temperature is changed to 150℃±20℃, the diameter is reduced by 1.0-1.5mm per pass, the feeding speed is 4~5m / min, and the final wire forming diameter is 3-4mm; The third rotary forging is based on the second rotary forging, the rotary forging temperature is changed to 80℃±20℃, the diameter is reduced by 0.5~0.7mm per pass, the feeding speed is 4~5m / min, and the final wire forming diameter is 1.0-1.5mm.

[0017] Furthermore, in S3 rotary forging, three rotary forgings are performed by combining room temperature operation and feed speed variation, specifically including: The first rotary forging is carried out at room temperature. The diameter is reduced by 1.7-2 mm per pass. The total diameter reduction rate is 2-3 m / min. The final wire diameter is 7-9 mm. The second rotary forging is based on the first rotary forging. The rotary forging temperature is room temperature, the diameter is reduced by 1.0-1.5mm per pass, the feeding speed is 4-5m / min, and the final wire forming diameter is 3-4mm. The third rotary forging is based on the second rotary forging. The rotary forging temperature is room temperature, the diameter is reduced by 0.3~0.5mm per pass, the feeding speed is 2~3m / min, and the final wire forming diameter is 1.0-1.5mm.

[0018] Furthermore, in S4 wire drawing, the annealing is performed under inert gas protection at 250-350° C. for 15-30 minutes before each drawing.

[0019] Furthermore, in the S4 wire drawing, the temperature during the drawing and the fine drawing is controlled at 120-180°C, preferably 140-150°C.

[0020] The present invention also protects the ultrafine magnesium alloy wire prepared by the preparation method of the ultrafine magnesium alloy wire, which has a diameter of 0.2-0.4 mm, a surface roughness Ra≤0.8 μm, a tensile strength of 250-310 MPa, and an elongation at break of 10%-30%.

[0021] The present invention also protects the use of the ultrafine magnesium alloy wire in the field of medical implants, such as for manufacturing orthopedic implants, anastomotic staples and cardiovascular stents.

[0022] Beneficial effects: In the preparation method of the ultrafine magnesium alloy wire provided by the present invention, the melted high-purity magnesium alloy billet is preheated at 150°C-300°C under the protection of inert gas or nitrogen by hot extrusion technology, and then extruded into a coil with a diameter of 10-15mm. The extruded magnesium alloy coil is subjected to room temperature rotary forging, and the rotary forging process parameters are a single-die deformation of 5-15%. The swaged wire is wound at the other end of the die by a winding machine, thereby forming continuous production. After multiple rotary forging passes, a thick wire with a diameter of 1-1.5mm is obtained. The thick wire is subjected to multiple stretching, annealing and surface brightening treatments at room temperature, and finally a magnesium alloy wire with a diameter of 0.2-0.4mm with uniform grain size, tensile strength ≥260MPa, and elongation at break ≥10% is obtained.

[0023] Furthermore, the rotary swaging process has three key parameters: swaging temperature, feed speed, and reduction per pass. Lower temperatures, greater reduction per pass, and slower feed speeds result in greater deformation of the thick wire, finer grains, and ultimately higher tensile strength and lower elongation at break (resulting in higher tensile strength but greater brittleness). Conversely, higher temperatures, smaller reduction per pass, and faster feed speeds result in less deformation, lowering the tensile strength of the thin wire but increasing its elongation at break (decreasing tensile strength but increasing toughness). These three parameters are coupled to determine the optimal range of deformation that the thick wire can tolerate. Therefore, it is crucial to properly control the swaging temperature, feed speed, and reduction per pass to avoid wire breakage caused by deformation exceeding the tolerable range. These three parameters independently influence the deformation of the thick wire in the rotary swaging die. This deformation should be neither too large nor too small; a balanced state is ideal.

[0024] In the preparation method of the ultrafine magnesium alloy wire provided by the present invention, the swaging process can include three stages, wherein the swaging focus of the first stage is to crush the residual coarse second phase and casting structure defects, significantly improve the dislocation density, and enable the material to initially obtain a tensile strength of 250MPa level, while retaining sufficient plasticity to support subsequent processing. The second and third stages release internal residual stress through low strain rate and fine deformation, eliminate surface microcracks, and further refine the grains to the submicron level, and promote the uniform dispersion and distribution of the nanoscale second phase, ultimately improving the tensile strength of the material, and the surface finish meets the medical grade requirements. After three-stage swaging, the wire diameter can be precisely controlled at 1.0-1.5mm, with both high strength and large elongation, and the microstructure presents the characteristics of coexistence of uniform fine grains and nano-precipitated phases. This process achieves the synergistic optimization of mechanical properties and microstructure through a gradient deformation strategy, and is fully adapted to the clinical needs of anastomosis staples, vascular stents, etc. that require high-strength, high-toughness, and degradable magnesium alloy wires.

[0025] Furthermore, the method for preparing ultrafine magnesium alloy wire provided by the present invention involves progressively drawing thick filaments to fine filaments with a diameter of 0.2-0.4 mm through cold drawing and intermediate annealing. Using a multi-pass drawing technique, the thick filaments are first subjected to 4-6 continuous reduction passes (10%-20% reduction per pass). Before each drawing pass, intermediate annealing is performed at 250-350°C under inert gas protection (holding temperature for 15-30 minutes) to eliminate work hardening and restore plasticity. During the drawing process, a graphite-based lubricant and a cemented carbide die (die angle 8°-12°) are used, and the drawing temperature is controlled at 120-180°C to enhance the plasticity of the magnesium alloy. Finally, a fine drawing pass (single-pass reduction rate ≤5%), combined with surface polishing, is performed to obtain high-precision fine filaments with a diameter of 0.2-0.4 mm and a surface roughness Ra ≤ 0.8 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings. Obviously, the drawings described below only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0027] Figure 1 It is a schematic diagram of the rotary forging die; Figure 2 It is a schematic diagram of the magnesium alloy disc being swaged into thick wire; Figure 3 This is the microstructure of the magnesium alloy filament produced in Example 1 of the present invention; Figure 4 3 is a graph showing the tensile test results of the magnesium alloy filament produced in Example 3 of the present invention. The elongation at break is calculated by measuring the length of the sample after fracture using the formula: (length of the gauge section after fracture - length of the original gauge section) / length of the original gauge section × 100%. DETAILED DESCRIPTION

[0028] The following are definitions of some terms used in the present invention. Other terms not mentioned here have definitions and meanings commonly known in the art: Ultrafine magnesium alloy wire: magnesium alloy wire with a diameter of less than 1mm, especially magnesium alloy wire with a diameter of 0.2-0.4mm.

[0029] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be realized in various forms and should not be limited by the embodiments set forth herein. In the examples, if specific techniques or conditions are not indicated, the techniques or conditions described in the literature in this area or the product specifications are carried out. Reagents used or instruments that are not indicated by manufacturers are conventional products that can be obtained commercially. In the following examples, if not clearly stated, "%" refers to percentage by weight.

[0030] Example 1 A method for preparing an ultrafine magnesium alloy wire comprises the following steps: S1 smelting: The magnesium alloy raw materials are heated to prepare alloy ingots. Specifically, high-purity magnesium and alloy element raw materials with a purity of >99.99% are baked and placed in a crucible. They are vacuumed twice and replaced with high-purity argon to reduce the risk of oxidation. Subsequently, they are induction heated until the raw materials are completely melted, and the temperature is raised to above 700°C for refining to remove impurities and uniform the composition. Finally, they are cast at 700°C±20°C to obtain a high-purity Mg alloy ingot with a diameter of 100mm. Based on the total amount of the magnesium alloy, the magnesium alloy contains the following elements in mass percentage: Zn: 1-5%, Ca: 0.01-1.5%, Mn: 0.01-0.5%, and the balance is Mg and unavoidable impurity elements. This smelting method effectively controls the purity of the alloy and the formation of the second phase through a vacuum environment and argon protection, providing a low-impurity and uniform composition ingot foundation for subsequent processing.

[0031] S2 extrusion: The alloy ingot is hot-pressed and extruded to obtain a disk with a diameter of 10-15 mm. Specifically, the high-purity magnesium alloy ingot prepared above is kept at 350℃±20℃ for 4 hours, and then hot extruded by an extruder in the temperature range of 300-400℃. A high extrusion ratio of 50-80 is used to significantly reduce the cross-section of the ingot from a diameter of 100 mm to a diameter of 10-15 mm. This step utilizes high-temperature dynamic recrystallization to refine the grains and crush the coarse second phase, ultimately obtaining a dense disk, which provides a matrix material with both uniform microstructure and excellent plasticity for subsequent rotary forging deformation.

[0032] S3 rotary forging: By combining temperature reduction and feed speed reduction, three rotary forgings are performed. Step 1: First Swaging The first pass, involving a large deformation, is performed. The swaging temperature is controlled within a range of 150°C ± 20°C, allowing for grain refinement through the synergistic effects of dynamic recrystallization and work hardening. Each pass reduces the diameter by 1mm, with a total feed rate of 5m / min, resulting in a final wire diameter of 7-9mm. This stage focuses on breaking down residual coarse secondary phases and casting defects, significantly increasing dislocation density.

[0033] Step 2: Second Forging Based on the first rotary forging, the rotary forging temperature was changed to 80℃±20℃, the diameter reduction per pass was only 0.5mm, the feeding speed was reduced to 4m / min, and the final wire forming diameter was 3-4mm.

[0034] Step 3: The third forging Based on the second rotary forging, the rotary forging temperature was changed to room temperature, the diameter reduction was only 0.2mm per pass, the feeding speed was reduced to 2m / min, and the final wire forming diameter was 1.0-1.5mm.

[0035] S4 wire drawing: The thick wire is drawn through multiple continuous reduction passes. Graphite-based lubricants and cemented carbide dies (die angle 8°-12°) are used during the drawing process. Before each drawing, the wire is kept warm for 20 minutes under the protection of an inert gas (high-purity argon) at 300°C. During the drawing, the temperature is controlled at 150°C, and the single-pass reduction rate is 10%, until the diameter is less than or equal to 0.6mm. Fine drawing is performed, and the temperature is controlled at 150°C, and the single-pass reduction rate is ≤5%, until the diameter is 0.3mm. Finally, an ultrafine magnesium alloy wire with a surface roughness Ra ≤ 0.8μm is obtained.

[0036] The microstructure of ultrafine magnesium alloy wire is tested, such as Figure 3 As shown, it can be seen that the grain sizes of the ultrafine magnesium alloy wires are roughly the same and evenly distributed.

[0037] Example 2 A method for preparing an ultrafine magnesium alloy wire comprises the following steps: S1 smelting: Mix and heat magnesium and alloy element raw materials to prepare alloy ingots. Specifically, high-purity magnesium and alloy element raw materials with a purity of >99.99% are baked and placed in a crucible. They are vacuumed twice and replaced with high-purity argon to reduce the risk of oxidation. Subsequently, they are induction heated until the raw materials are completely melted, and the temperature is raised to above 700°C for refining to remove impurities and uniform the composition. Finally, they are cast at 700°C±20°C to obtain a high-purity Mg alloy ingot with a diameter of 100mm. Based on the total amount of the magnesium alloy, in terms of mass percentage, the magnesium alloy contains the following elements: Zn: 1-5%, Ca: 0.01-1.5%, Mn: 0.01-0.5%, and the balance is Mg and unavoidable impurity elements.

[0038] S2 Extrusion: The alloy ingot is hot-pressed and extruded to produce a coil with a diameter of 10-15 mm. Specifically, the high-purity magnesium alloy ingot prepared above is held at 350°C ± 20°C for 4 hours. It is then hot-extruded through an extruder at a temperature range of 300-400°C, using a high extrusion ratio of 50-80 to significantly reduce the ingot's cross-section from a diameter of 100 mm to a diameter of 10-15 mm.

[0039] S3 rotary forging: By combining temperature reduction and constant feed speed, three rotary forgings are performed. Step 1: First Swaging The first pass, involving large deformation, is performed, with the swaging temperature controlled within the range of 200°C ± 20°C. Dynamic recrystallization and work hardening combine to refine the grains. Each pass reduces the diameter by 2mm, with a total feed rate of 5m / min, resulting in a final wire diameter of 7-9mm. This stage focuses on breaking down residual coarse secondary phases and casting defects, significantly increasing dislocation density.

[0040] Step 2: Second Forging Based on the first rotary forging, the rotary forging temperature is changed to 150℃±20℃, the diameter is reduced by 1.0-1.5mm in each pass, the feeding speed is 5m / min, and the final wire forming diameter is 3-4mm.

[0041] Step 3: The third forging Based on the second rotary forging, the rotary forging temperature was changed to 80℃±20℃, the diameter reduction per pass was only 0.5mm, the feeding speed was 5m / min, and the final wire forming diameter was 1.0-1.5mm.

[0042] S4 wire drawing: The thick wire is drawn through multiple continuous reduction passes. Graphite-based lubricants and carbide dies (die angle 8°-12°) are used during the drawing process. Before each drawing, the wire is kept warm for 20 minutes under the protection of an inert gas (high-purity argon) at 300°C. During the drawing, the temperature is controlled at 150°C, and the single-pass reduction rate is 10%, until the diameter is less than or equal to 0.6mm. Fine drawing is performed, and the temperature is controlled at 150°C, and the single-pass reduction rate is ≤5%, until the diameter is 0.3mm, to obtain an ultrafine magnesium alloy wire with a surface roughness Ra ≤ 0.8μm.

[0043] Example 3 A method for preparing an ultrafine magnesium alloy wire comprises the following steps: S1 smelting: Mix and heat magnesium and alloy element raw materials to prepare alloy ingots. Specifically, high-purity magnesium and alloy element raw materials with a purity of >99.99% are baked and placed in a crucible. They are vacuumed twice and replaced with high-purity argon to reduce the risk of oxidation. Subsequently, they are induction heated until the raw materials are completely melted, and the temperature is raised to above 700°C for refining to remove impurities and uniform the composition. Finally, they are cast at 700°C±20°C to obtain a high-purity Mg alloy ingot with a diameter of 100mm. Based on the total amount of the magnesium alloy, in terms of mass percentage, the magnesium alloy contains the following elements: Zn: 1-5%, Ca: 0.01-1.5%, Mn: 0.01-0.5%, and the balance is Mg and unavoidable impurity elements.

[0044] S2 Extrusion: The alloy ingot is hot-pressed and extruded to produce a coil with a diameter of 10-15 mm. Specifically, the high-purity magnesium alloy ingot prepared above is held at 350°C ± 20°C for 4 hours. It is then hot-extruded through an extruder at a temperature range of 300-400°C, using a high extrusion ratio of 50-80 to significantly reduce the ingot's cross-section from a diameter of 100 mm to a diameter of 10-15 mm.

[0045] S3 rotary forging: By combining room temperature operation and feed speed changes, three rotary forgings are performed. Step 1: First Swaging The first pass, involving a large deformation, is performed. The swaging temperature is kept within room temperature, allowing for grain refinement through the synergistic effects of dynamic recrystallization and work hardening. Each pass reduces the wire diameter by 2mm, with a total reduction rate of 3m / min, resulting in a final wire diameter of 7-9mm. This stage focuses on breaking down residual coarse secondary phases and casting defects, significantly increasing dislocation density.

[0046] Step 2: Second Forging Based on the first rotary forging, the rotary forging temperature is room temperature, the diameter is reduced by 1.0-1.5 mm per pass, the feeding speed is 4 m / min, and the final wire forming diameter is 3-4 mm.

[0047] Step 3: The third forging Based on the second rotary forging, the rotary forging temperature is room temperature, the diameter reduction per pass is only 0.5 mm, the feeding speed is 2 m / min, and the final wire forming diameter is 1.0-1.5 mm.

[0048] S4 wire drawing: The thick wire is drawn through multiple continuous reduction passes. Graphite-based lubricants and carbide dies (die angle 8°-12°) are used during the drawing process. Before each drawing, the wire is kept warm for 20 minutes under the protection of an inert gas (high-purity argon) at 300°C. During the drawing, the temperature is controlled at 150°C, and the single-pass reduction rate is 10%, until the diameter is less than or equal to 0.6mm. Fine drawing is performed, and the temperature is controlled at 150°C, and the single-pass reduction rate is ≤5%, until the diameter is 0.3mm, to obtain an ultrafine magnesium alloy wire with a surface roughness Ra ≤ 0.8μm.

[0049] Comparative Example 1 Referring to Example 3, a method for preparing an ultrafine magnesium alloy wire comprises the following steps: S1 smelting: Mix and heat magnesium and alloy element raw materials to prepare alloy ingots. Specifically, high-purity magnesium and alloy element raw materials with a purity of >99.99% are baked and placed in a crucible. They are vacuumed twice and replaced with high-purity argon to reduce the risk of oxidation. Subsequently, they are induction heated until the raw materials are completely melted, and the temperature is raised to above 700°C for refining to remove impurities and uniform the composition. Finally, they are cast at 700°C±20°C to obtain a high-purity Mg alloy ingot with a diameter of 100mm. Based on the total amount of the magnesium alloy, in terms of mass percentage, the magnesium alloy contains the following elements: Zn: 1-5%, Ca: 0.01-1.5%, Mn: 0.01-0.5%, and the balance is Mg and unavoidable impurity elements.

[0050] S2 Extrusion: The alloy ingot is hot-pressed and extruded to produce a coil with a diameter of 10-15 mm. Specifically, the high-purity magnesium alloy ingot prepared above is held at 350°C ± 20°C for 4 hours. It is then hot-extruded through an extruder at a temperature range of 300-400°C, using a high extrusion ratio of 50-80 to significantly reduce the ingot's cross-section from a diameter of 100 mm to a diameter of 10-15 mm.

[0051] S3 rotary forging: By combining room temperature operation and feed speed changes, three rotary forgings are performed. Step 1: First Swaging The first pass, involving a large deformation, is performed. The swaging temperature is kept within room temperature, allowing for grain refinement through the synergistic effects of dynamic recrystallization and work hardening. Each pass reduces the diameter by 1mm, with a total reduction rate of 2m / min, resulting in a final wire diameter of 7-9mm. This stage focuses on breaking down residual coarse secondary phases and casting defects, significantly increasing dislocation density.

[0052] Step 2: Second Forging Based on the first rotary forging, the rotary forging temperature is room temperature, the diameter is reduced by 0.5-1.0 mm per pass, the feeding speed is 2 m / min, and the final wire forming diameter is 3-4 mm.

[0053] Step 3: The third forging On the basis of the second swaging, the swaging temperature was room temperature, the diameter reduction was only 0.5mm per pass, and the feeding speed was 2m / min. During the swaging process, the wire material broke and could not be reeled.

[0054] Comparative Example 2 Referring to Example 3, a method for preparing an ultrafine magnesium alloy wire comprises the following steps: S1 smelting: Mix and heat magnesium and alloy element raw materials to prepare alloy ingots. Specifically, high-purity magnesium and alloy element raw materials with a purity of >99.99% are baked and placed in a crucible. They are vacuumed twice and replaced with high-purity argon to reduce the risk of oxidation. Subsequently, they are induction heated until the raw materials are completely melted, and the temperature is raised to above 700°C for refining to remove impurities and uniform the composition. Finally, they are cast at 700°C±20°C to obtain a high-purity Mg alloy ingot with a diameter of 100mm. Based on the total amount of the magnesium alloy, in terms of mass percentage, the magnesium alloy contains the following elements: Zn: 1-5%, Ca: 0.01-1.5%, Mn: 0.01-0.5%, and the balance is Mg and unavoidable impurity elements.

[0055] S2 Extrusion: The alloy ingot is hot-pressed and extruded to produce a coil with a diameter of 10-15 mm. Specifically, the high-purity magnesium alloy ingot prepared above is held at 350°C ± 20°C for 4 hours. It is then hot-extruded through an extruder at a temperature range of 300-400°C, using a high extrusion ratio of 50-80 to significantly reduce the ingot's cross-section from a diameter of 100 mm to a diameter of 10-15 mm.

[0056] S3 rotary forging: By combining room temperature operation and feed speed changes, three rotary forgings are performed. Step 1: First Swaging The first pass, involving a large deformation, is performed. The swaging temperature is kept within room temperature, allowing for grain refinement through the synergistic effects of dynamic recrystallization and work hardening. Each pass reduces the wire diameter by 2mm, with a total reduction rate of 3m / min, resulting in a final wire diameter of 7-9mm. This stage focuses on breaking down residual coarse secondary phases and casting defects, significantly increasing dislocation density.

[0057] Step 2: Second Forging Based on the first rotary forging, the rotary forging temperature is room temperature, the diameter is reduced by 1.0-1.5 mm per pass, the feeding speed is 4 m / min, and the final wire forming diameter is 3-4 mm.

[0058] Step 3: The third forging Based on the second rotary forging, the rotary forging temperature is room temperature, the diameter reduction per pass is only 0.5 mm, the feeding speed is 2 m / min, and the final wire forming diameter is 1.0-1.5 mm.

[0059] S4 wire drawing: The thick wire is drawn through multiple continuous reduction passes. Graphite-based lubricants and carbide dies (die angle 8°-12°) are used during the drawing process. Before each drawing, the wire is kept warm for 20 minutes under the protection of inert gas (high-purity argon) at 300°C. During the drawing, the temperature is controlled at 150°C, and the single-pass reduction rate is 5% until the diameter is 0.3mm. The wire breaks during the drawing process and cannot be reeled.

[0060] Performance Testing The mechanical properties of the prepared ultrafine magnesium alloy wire were tested, and the results are shown in Table 1.

[0061] Table 1 Mechanical properties test results of ultrafine magnesium alloy wire

[0062] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0063] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0064] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing an ultrafine magnesium alloy wire, characterized in that: The following steps are involved: S1 smelting: heating the magnesium alloy raw material to prepare an alloy ingot; S2 extrusion: hot pressing and extruding the alloy ingot to obtain a disk with a diameter of 10-15 mm; S3 rotary swaging: performing rotary swaging on the coil N times, where N is a positive integer greater than or equal to 3, to obtain a thick wire; wherein the temperature is controlled at 20-250° C., the feeding speed is 1-5 m / min, and the diameter reduction per pass is 0.1-3 mm; S4 wire drawing: The thick wire is subjected to multiple continuous diameter reduction drawing, annealing is performed before each drawing, and then drawing is performed. During drawing, the single-pass diameter reduction rate is controlled to be 10%-20%, until the diameter is less than or equal to 0.6 mm, and fine drawing is performed, and the single-pass diameter reduction rate is controlled to be ≤5% until the diameter is 0.2-0.4 mm, and the surface is polished to obtain an ultrafine magnesium alloy wire.

2. The method for preparing the ultrafine magnesium alloy wire according to claim 1, characterized in that: In S1 smelting, the heating adopts an oxygen-free environment, preferably an argon atmosphere, and the temperature is first raised to above 700°C for refining, and then cast at 700°C±20°C to obtain the alloy ingot. The alloy ingot contains the following elements, in terms of mass percentage: Zn: 1-5%, Ca: 0.01-1.5%, Mn: 0.01-0.5%, and the balance is Mg and unavoidable impurity elements.

3. The method for preparing the ultrafine magnesium alloy wire according to claim 1 or 2, characterized in that: In S2 extrusion, the hot pressing extrusion includes first keeping the alloy ingot at 350°C ± 20°C for 3 to 6 hours, and then extruding it at 300-400°C and an extrusion ratio of 50-80.

4. The method for preparing the ultrafine magnesium alloy wire according to claim 3, characterized in that: In S3 rotary forging, three rotary forgings are performed by combining temperature reduction and feed speed reduction, specifically including: In the first rotary forging, the rotary forging temperature is controlled at 150℃±20℃, the diameter is reduced by 1~1.2mm per pass, the total diameter reduction is at a feeding speed of 4.5~5m / min, and the final wire forming diameter is 7-9mm; The second rotary forging is based on the first rotary forging, the rotary forging temperature is changed to 80℃±20℃, the diameter is reduced by 0.4~0.5mm per pass, the feeding speed is reduced to 3.5~4m / min, and the final wire forming diameter is 3-4mm; The third rotary forging is based on the second rotary forging. The rotary forging temperature is changed to room temperature, the diameter is reduced by 0.2~0.3mm per pass, the feeding speed is reduced to 2~2.5m / min, and the final wire forming diameter is 1.0-1.5mm.

5. The method for preparing the ultrafine magnesium alloy wire according to claim 3, wherein: In S3 rotary forging, three rotary forgings are performed by combining temperature reduction and constant feed speed, specifically including: In the first rotary forging, the rotary forging temperature is controlled at 200℃±20℃, the diameter is reduced by 2~2.5mm per pass, the total diameter reduction rate is 4~5m / min, and the final wire forming diameter is 7-9mm; The second rotary forging is based on the first rotary forging, and the rotary forging temperature is changed to 150℃±20℃, the diameter is reduced by 1.0-1.5mm per pass, the feeding speed is 4~5m / min, and the final wire forming diameter is 3-4mm; The third rotary forging is based on the second rotary forging, the rotary forging temperature is changed to 80℃±20℃, the diameter is reduced by 0.5~0.7mm per pass, the feeding speed is 4~5m / min, and the final wire forming diameter is 1.0-1.5mm.

6. The method for preparing the ultrafine magnesium alloy wire according to claim 3, characterized in that: In S3 rotary forging, three rotary forgings are performed by combining room temperature operation and feed speed changes, specifically including: The first rotary forging is carried out at room temperature. The diameter is reduced by 1.7-2 mm per pass. The total diameter reduction rate is 2-3 m / min. The final wire diameter is 7-9 mm. The second rotary forging is based on the first rotary forging. The rotary forging temperature is room temperature, the diameter is reduced by 1.0-1.5mm per pass, the feeding speed is 4-5m / min, and the final wire forming diameter is 3-4mm. The third rotary forging is based on the second rotary forging. The rotary forging temperature is room temperature, the diameter is reduced by 0.3~0.5mm per pass, the feeding speed is 2~3m / min, and the final wire forming diameter is 1.0-1.5mm.

7. The method for preparing the ultrafine magnesium alloy wire according to any one of claims 4 to 6, characterized in that: In S4 wire drawing, the annealing is carried out under inert gas protection at 250-350° C. for 15-30 minutes before each drawing.

8. The method for preparing the ultrafine magnesium alloy wire according to claim 7, characterized in that: In S4 wire drawing, the temperature during the drawing and the fine drawing is controlled at 120-180°C, preferably 140-150°C.

9. The ultrafine magnesium alloy wire prepared by the method for preparing an ultrafine magnesium alloy wire according to any one of claims 1 to 8, characterized in that: The ultrafine magnesium alloy wire has a diameter of 0.2-0.4 mm, a surface roughness Ra≤0.8 μm, a tensile strength of 250-310 MPa, and an elongation at break of 10%-30%.

10. Use of the ultrafine magnesium alloy wire according to claim 9 in the field of medical implants.

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