CN106917022A - A kind of preparation method of biological medical magnesium alloy silk - Google Patents

Abstract

A method for preparing biomedical magnesium alloy wire belongs to the technical field of metal materials. After melting magnesium and zinc, stirring and refining, casting them into alloy ingots, and then performing homogenization heat treatment on the alloy ingots, or without The heat treatment is directly carried out by equal-channel extrusion, and finally the magnesium-zinc alloy by equal-channel extrusion is processed into wire by multi-pass drawing. When the wire drawing is completed, the single-phase supersaturated solid solution structure is obtained, and its strength and elongation are higher than those obtained by direct drawing without equal channel extrusion, which not only meets the requirements of strength and plasticity, but also makes the material The corrosion resistance performance has been greatly improved.

Description

A kind of preparation method of biomedical magnesium alloy wire

technical field

The invention belongs to the technical field of metal materials, and relates to a preparation technology of a magnesium alloy, in particular to a preparation method of a magnesium alloy wire for biomedical use.

Background technique

Biomedical magnesium alloy wire, as a degradable material, has broad application prospects in the biomedical field. It can be used as a raw material for human implanted medical devices such as degradable anastomotic wire, degradable esophageal stent, and degradable bladder stent. According to the requirements of clinical use, biomedical magnesium alloy wire should have high room temperature strength and plasticity to meet the requirements of the support integrity of implanted materials in the human body, and at the same time, in order to prevent the implanted device from corroding too quickly in the human body It also requires biomedical magnesium alloy wire to have better biocorrosion corrosion resistance. Magnesium alloy is a material with active chemical properties and poor processing and forming performance. Adding a small amount of zinc element as an alloying element in magnesium can significantly improve corrosion resistance and processing performance. The performance hit is huge. Zinc has a large solubility in magnesium, and its solubility in magnesium will also change greatly with the change of temperature. At 325 ° C, the solubility of zinc in magnesium under equilibrium conditions is about 6% by mass. Various mesophases are formed when zinc is desolvated in magnesium. In order to meet the performance requirements of biomedical magnesium alloy wire, it is necessary to completely dissolve zinc in magnesium to obtain a single-phase supersaturated solid solution structure, which can not only meet the requirements of strength and plasticity, but also make the material have better corrosion resistance. sex.

The traditional preparation method of magnesium alloy wire is multi-pass drawing at room temperature or high temperature. The advantage of room temperature forming is that the process conditions are easy to control, and the surface quality and strength of the wire are high. However, the deformation of the magnesium alloy at room temperature is low, so there are many drawing passes, and annealing is required to eliminate work hardening during the drawing process. plasticity is also low. Although high-temperature stretching will result in poor surface quality, the plasticity of the wire is better, and the single-pass drawing deformation is large, the drawing passes are few, and no additional heat treatment is required during the processing. The high-temperature multi-pass drawing process is more beneficial to the forming of magnesium alloy wire. From the previous application results, because the eutectic formed in the cast state in the magnesium-zinc alloy has a great influence on the uniformity of deformation, the coarse eutectic will be broken after multi-pass drawing, but due to its distribution Unevenness will cause uneven deformation of each part during the deformation process, which will easily cause breakage. In order to solve this problem, it is necessary to homogenize the material before preparing the wire. The usual process is to heat the cast magnesium-zinc alloy to 300 to 350°C and keep it warm for a long time to decompose and dissolve the massive eutectic. However, this method has two disadvantages. One is that long-time heating causes coarse grains, which reduces the mechanical properties and processing properties of the material. It is difficult to obtain the organization of single-phase supersaturated solid solution.

Contents of the invention

The purpose of the present invention is to aim at the traditional magnesium alloy wire preparation method, the room temperature forming deformation is low, the drawing passes are many, the drawing process needs annealing to eliminate work hardening, and the plasticity of the wire is also low; Heating for a long time causes coarse grains, material mechanical properties and processing properties to decline, and it is difficult to completely dissolve the second phase in the matrix after long-term homogenization treatment, and it is difficult to obtain single-phase supersaturated solid solutions. Based on the preparation method of the biomedical magnesium alloy wire, a single-phase supersaturated solid solution structure can be obtained, which can not only meet the requirements of strength and plasticity, but also make the material have better corrosion resistance.

The technical solution of the present invention is: a preparation method of biomedical magnesium alloy wire, which is characterized in that it comprises the following steps:

(1) Metal magnesium and metal zinc are melted into liquid metal;

(2) Stirring and refining the liquid metal in step (1) to obtain refined liquid metal, mechanically stirring the molten metal for 3 to 5 minutes, then allowing the molten slag to float and then removing the slag;

(3) casting the refined liquid metal in step (2) into an alloy ingot;

(4) Perform homogenization heat treatment on the alloy ingot obtained in step (3) or directly perform equal-channel extrusion without heat treatment, the homogenization treatment temperature is 300-350 ° C, and the time is 2-6 hours; equal-channel angular extrusion The pressing temperature is between 200°C and 300°C, and the cumulative deformation is required to be over 400%;

(5) The material after medium channel extrusion in step (4) is processed into wire by multi-pass drawing. Before drawing, it is preheated at 300°C for 10 minutes, and the drawing temperature is about 300°C. Single-pass deformation The amount is 10% to 30%, and the drawing speed is 10mm/s to 40mm/s.

The mass percentage of the zinc element in the alloy ingot in the step (3) is 3.0%-6.0%.

The temperature range of the equal-channel extrusion in step (4) is 200-300° C., and the equal-channel deformation is above 400%, so that the material can be fully deformed.

The beneficial effects of the present invention are: the preparation method of a biomedical magnesium alloy wire proposed by the present invention has a clear preparation principle. By performing severe plastic deformation treatment on the magnesium-zinc alloy first, when the strain amount is large enough, the original thick second The phase is broken into small particles, and at the same time, the grains will be significantly refined and there will be a large number of crystal defects such as dislocations and vacancies. The greater the number of phase interfaces per unit volume, the faster the diffusion rate, and the shorter the distance that solute atoms need to diffuse. A large number of grain defects in the material are very beneficial to the diffusion of zinc in the matrix. In the subsequent drawing process, the material is heated to 300 ° C and deformed. Under the action of dynamic recrystallization, the grain size is maintained in a finer state, and the second phase is dissolved during the deformation process until it is completely solid. Dissolved into the matrix, when the wire drawing is completed, a single-phase supersaturated solid solution structure is obtained, and its strength and elongation are higher than those obtained by direct drawing without equal channel extrusion, which not only meets the requirements of strength and plasticity The corrosion resistance of the material has also been greatly improved.

Description of drawings

Figure 1 is a scanning electron micrograph of the Mg-6%wt.Zn alloy in the extruded state.

Fig. 2 is a scanning electron micrograph at 200°C under 6-pass equal-channel extrusion.

Fig. 3 is a scanning electron micrograph of the extruded state directly drawn into a wire.

Fig. 4 is a scanning electron micrograph of a wire drawn into an extruded state through equal channel extrusion.

Fig. 5 is a schematic diagram of the mechanical properties of raw materials and wires in the present invention.

detailed description

The present invention will be further described below in conjunction with embodiment:

A method for preparing a biomedical magnesium alloy wire, comprising the following steps:

(1) Metal magnesium and metal zinc are melted into liquid metal;

(2) Stirring and refining the liquid metal in step (1) to obtain refined liquid metal, mechanically stirring the molten metal for 3 to 5 minutes after melting, then allowing the molten slag to float and remove the slag;

(3) casting the refined liquid metal in step (2) into an alloy ingot;

(4) Perform homogenization heat treatment on the alloy ingot obtained in step (3) or directly perform equal-channel extrusion without heat treatment, the homogenization treatment temperature is 300-350 ° C, and the time is 2-6 hours; equal-channel angular extrusion The pressing temperature is between 200°C and 300°C, and the cumulative deformation is required to be over 400%;

(5) The material after medium channel extrusion in step (4) is processed into wire by multi-pass drawing. Before drawing, it is preheated at 300°C for 10 minutes, and the drawing temperature is about 300°C. Single-pass deformation The amount is 10% to 30%, and the drawing speed is 10mm/s to 40mm/s.

A method for preparing biomedical magnesium alloy wire, the mass percentage of zinc element in the alloy ingot in step (3) is 3.0% to 6.0%; the temperature range of medium channel extrusion in step (4) is 200 to 300°C The amount of deformation is more than 400%, so that the material can be fully deformed.

The principle of a preparation method of a biomedical magnesium alloy wire is as follows: the magnesium-zinc alloy is first subjected to severe plastic deformation treatment. When the strain is large enough, the original coarse second phase is broken into small particles, and the grains will be significantly refined at the same time. And there are a large number of crystal defects such as dislocations and vacancies. The greater the number of phase interfaces per unit volume, the faster the diffusion rate, and the shorter the distance that solute atoms need to diffuse. A large number of grain defects in the material are very beneficial to the diffusion of zinc in the matrix. In the subsequent drawing process, the material is heated to 300 ° C and deformed. Under the action of dynamic recrystallization, the grain size is maintained in a finer state, and the second phase is dissolved during the deformation process until it is completely solid. Dissolved into the matrix, when the wire drawing is completed, a single-phase supersaturated solid solution structure is obtained, and its strength and elongation are higher than those obtained by direct drawing without equal channel extrusion.

Example 1:

As shown in Figures 1 to 4, a preparation method of biomedical magnesium alloy wire, there is a large eutectic phase in the structure of the Mg-6%wt.Zn alloy after casting and extrusion, as shown in Figure 1, the extruded After the compressed sample was subjected to equal-channel extrusion treatment at 200 °C for 6 passes, the number of mesophases decreased, the size decreased, and a large number of fine precipitates were precipitated, as shown in Figure 2. After the extruded sample is drawn into a wire with a diameter of 0.3mm, there are a large number of mesophases distributed in bands in the microstructure, and the area between the mesophases distributed in bands appears due to uneven deformation. Microcracks and holes, as shown in Figure 3. However, in the microstructure of the wire drawn after multi-pass equal-channel extrusion, there is almost no second phase precipitation, the structure is uniform, and there are no cracks and holes, as shown in Figure 4.

As shown in Figure 5, a preparation method of biomedical magnesium alloy wire, the yield strength and tensile strength of the extruded Mg-6%wt.Zn alloy are 200MPa and 260MPa respectively, and the elongation is 18%. The yield strength and tensile strength of the Mg-6%wt.Zn alloy after 6 passes of equal channel extrusion at 200°C are 208MPa and 255MPa respectively, and the elongation is 24%. The strength does not increase significantly, but the elongation increases significantly. . The yield strength, tensile strength and elongation of the wire with a diameter of 0.3 mm at room temperature were 190 MPa, 240 MPa and 4.5% respectively at room temperature without direct drawing through equal channel extrusion, while the drawing after equal channel extrusion The yield strength, tensile strength and elongation of the direct 0.3mm wire at room temperature are 210MPa, 300MPa and 11%, respectively. The results show that the new technology can effectively improve the mechanical properties of biomedical magnesium alloy wire.

The preparation principle of the present invention is clear. By performing severe plastic deformation treatment on the magnesium-zinc alloy first, when the strain is large enough, the original coarse second phase is broken into small particles, and at the same time, the grains will be significantly refined and there will be a large number of dislocations and vacancies. and other crystal defects. The greater the number of phase interfaces per unit volume, the faster the diffusion rate, and the shorter the distance that solute atoms need to diffuse. A large number of grain defects in the material are very beneficial to the diffusion of zinc in the matrix. In the subsequent drawing process, the material is heated to 300 ° C and deformed. Under the action of dynamic recrystallization, the grain size is maintained in a finer state, and the second phase is dissolved during the deformation process until it is completely solid. Dissolved into the matrix, when the wire drawing is completed, a single-phase supersaturated solid solution structure is obtained, and its strength and elongation are higher than those obtained by direct drawing without equal channel extrusion, which not only meets the requirements of strength and plasticity The corrosion resistance of the material has also been greatly improved.

Claims (3)

1. A preparation method of biomedical magnesium alloy wire, characterized in that, comprising the following steps: (1) Metal magnesium and metal zinc are melted into liquid metal; (2) Stirring and refining the liquid metal in step (1) to obtain refined liquid metal, mechanically stirring the molten metal for 3 to 5 minutes after melting, then allowing the molten slag to float and remove the slag; (3) casting the refined liquid metal in step (2) into an alloy ingot; (4) Perform homogenization heat treatment on the alloy ingot obtained in step (3) or directly perform equal-channel extrusion without heat treatment, the homogenization treatment temperature is 300-350 ° C, and the time is 2-6 hours; equal-channel angular extrusion The pressing temperature is between 200°C and 300°C, and the cumulative deformation is required to be over 400%; (5) The material after medium channel extrusion in step (4) is processed into wire by multi-pass drawing. Before drawing, it is preheated at 300°C for 10 minutes, and the drawing temperature is about 300°C. Single-pass deformation The amount is 10% to 30%, and the drawing speed is 10mm/s to 40mm/s. 2. A method for preparing biomedical magnesium alloy wire, characterized in that: the mass percentage of zinc element in the alloy ingot described in step (3) is 3.0% to 6.0%. 3. A preparation method for biomedical magnesium alloy wire, characterized in that: the temperature range of equal channel extrusion described in step (4) is 200 to 300°C, and the equal channel deformation is more than 400%, so that the material is fully out of shape.