CN104862566A - High-strength high-plasticity medical magnesium alloy, and preparation method and applications thereof - Google Patents

Abstract

The invention discloses a high-strength and high-plasticity medical magnesium alloy, a preparation method and application thereof, and belongs to the technical field of medical magnesium alloy materials. By adding Zn, Nd, and Mn as alloy elements in the magnesium matrix, and extruding the magnesium alloy, the plastic deformation ability of the magnesium alloy is significantly improved, and by increasing the content of Zn element in the alloy, the resistance of the magnesium alloy is improved. The tensile strength has been greatly improved. The weight percentage of the new medical magnesium alloy components is: 0.2-6.0Zn, 0.5-2.0Nd, 0.5Mn, and the weight percentage of the restricted impurity content is: Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg. The alloy ingot of the present invention is subjected to homogenization treatment at 400-550° C. for 10 hours, and then extruded at 390° C. with an extrusion ratio of 36:1, and the lubricant is animal oil. The room temperature tensile strength of the alloy of the invention can reach up to 300MPa, and the elongation can reach up to 37%.

Description

A high-strength and high-plasticity medical magnesium alloy and its preparation process and application

technical field

The invention relates to the technical field of magnesium alloy materials, in particular to a high-strength and high-plasticity medical magnesium alloy and its preparation process and application. The magnesium alloy is used as a degradable metal implant material.

Background technique

In recent years, magnesium alloy, as a new generation of biodegradable biomedical materials, has become a frontier topic in biomaterials research. Compared with traditional inert metal implant materials (such as stainless steel, cobalt-chromium alloy, titanium alloy, etc.), magnesium alloy can be completely degraded after the patient recovers from treatment, and does not require secondary surgery to remove it, reducing the pain and cost of the patient. Magnesium alloys have the good mechanical properties and processing properties of metal materials. At the same time, magnesium is an essential trace element for the human body and participates in many physiological activities of the human body. Therefore, magnesium exhibits excellent biocompatibility. Many studies have shown that magnesium alloys also have a variety of biological functions. Therefore, magnesium alloy is expected to become an ideal biodegradable metal implant material due to its excellent comprehensive properties.

With the continuous expansion of the field of research and application of magnesium alloys as biomaterials, the performance requirements for magnesium alloys are becoming higher and higher and more diverse. For example, magnesium alloy is used as a degradable cardiovascular stent material. The stent will undergo large plastic deformation during use. Magnesium alloy must have sufficient strength; as a degradable suture material, the knotting process of suture also requires magnesium alloy to have excellent plastic deformation ability, and suture must also have high strength. Provide sufficient tension to fix the wound; when magnesium alloys are used as degradable bone nails, bone plates or bone filling materials, the strength requirements for magnesium alloys are relatively high. However, due to the close-packed hexagonal crystal structure, the plastic deformation performance of magnesium alloys is very limited, and the strength is low. It is necessary to improve the plastic deformation ability and strength of magnesium alloys through reasonable alloying design, heat treatment system, and optimized processing technology. .

Contents of the invention

The object of the present invention is to provide a high-strength and high-plasticity medical magnesium alloy and its preparation process and application. The alloy not only has good plastic deformation ability, but also has relatively high strength and is non-toxic.

Technical scheme of the present invention is:

A high-strength and high-plasticity medical magnesium alloy, by weight percentage, its chemical composition is: Zn0.2-6.0%, Mn0.15-0.5% (preferably 0.5%), Nd0.5-2.0%, limit the content of impurity elements It is: Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg.

The preparation technology of alloy of the present invention comprises the steps:

(1) Homogenization treatment: The magnesium alloy ingot is subjected to homogenization heat treatment at 400-550°C for 10 hours in a vacuum heat treatment furnace to homogenize the composition and structure of the ingot, and then water-cooled to form a supersaturated solid solution ;

(2) Extrusion treatment: before extrusion, the ingot is preheated in the furnace at 390°C for 2 hours, and then extruded at 380°C, the extrusion ratio is 36:1, the extrusion speed is 4m/min, and animal oil is used as lubricating oil , so as to obtain the medical magnesium alloy.

The preparation steps of the magnesium alloy ingot described in the above step (1) are as follows:

(a) Ingredients: According to different composition designs, the ingredients are prepared first, including Mg ingots with a purity of 99.99%, Zn ingots with a purity of 99.99%, Mg-30Nd master alloys with a purity of 99.99%, and electrolytic Mn powder;

(b) Alloy smelting and casting: add preheated Mg ingot, Zn ingot, and electrolytic Mn powder into the melting furnace, and the alloy melting temperature is 700°C; Continue smelting at 720°C for 30 minutes, stirring twice to make the melt uniform; during alloy smelting, continuously feed protective gas; cool down to 700°C and let stand for 15-30 minutes to allow inclusions to settle, then skim off The surface scum is cast into a graphite mold, which has a slightly flared mouth to prevent the occurrence of large shrinkage cavities, and finally obtain a high-purity medical magnesium alloy ingot.

The medical magnesium alloy is used as a degradable metal implant material, such as a degradable cardiovascular stent material, a degradable suture material, a degradable bone nail, a bone plate or a bone filling material and the like.

The magnesium alloy design principle of the present invention is as follows:

The invention relates to a novel high-strength and high-plastic deformation magnesium alloy containing Zn, Mn and rare earth element Nd, which is formed by adding metal elements Zn, Mn and rare earth element Nd into magnesium as alloy elements. Zn element has high solubility in the magnesium matrix and has obvious solid solution strengthening effect, which can significantly improve the strength of the material; the addition of a small amount of Mn element helps to eliminate the influence of impurity Fe on the corrosion resistance of magnesium alloys; Nd element a On the one hand, it can refine the recrystallized grains of the deformed magnesium alloy, and it can also weaken the texture strength of the deformed magnesium alloy. The strength, plasticity and corrosion resistance of magnesium alloys can be improved through the joint action of the three alloying elements Zn, Mn and Nd. The as-cast magnesium alloy is homogenized at 400-550° C. for 10 hours, and then water-cooled to obtain a magnesium alloy extrusion billet with uniform composition and structure. The magnesium alloy is preheated at 390°C for 2 hours before extrusion, the extrusion temperature is 380°C, the extrusion ratio is 36:1, and the extrusion exit speed is 4m/min to obtain a magnesium alloy rod with a diameter of 10mm, which has extremely high plasticity Deformation properties and high tensile strength, as well as very good corrosion resistance.

The beneficial effects of the present invention are as follows:

1. The present invention adds Zn, Nd, and Mn as alloying elements in the magnesium matrix, and extrudes the magnesium alloy, so that the plastic deformation ability of the magnesium alloy is significantly improved, and by increasing the content of the Zn element in the alloy, the The tensile strength of magnesium alloy has been greatly improved.

2. The novel high-strength and high-plastic deformation magnesium alloy containing Zn, Mn and rare earth element Nd prepared by the present invention has a room-temperature tensile strength of up to 300 MPa and a maximum elongation at break of 37%.

3. The magnesium alloy of the present invention is used as a degradable cardiovascular stent material. The stent can withstand large plastic deformation during use. In the process of in vivo service, the magnesium alloy stent has sufficient strength to provide continuous and sufficient support for blood vessels at the site of lesion stenosis. Supporting force; when it is used as a degradable suture material, the excellent plastic deformation ability of magnesium alloy meets the requirements of the suture during the knotting process, and the suture also has high strength, providing sufficient tension for the wound to fix the wound; The strength of the magnesium alloy makes it suitable for use as a degradable bone nail, bone plate or bone filling material.

Detailed ways

The present invention will be further described below in conjunction with examples.

Example 1:

The composition design (percentage by weight) of the magnesium alloy is: 0.2Zn, 0.5Mn, 2.0Nd, the weight percent of the restricted impurity elements is Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg. Prepare the alloy according to the above ingredients, add preheated Mg ingot, Zn ingot, and electrolytic Mn powder into the melting furnace, and the alloy melting temperature is 700°C. After all the ingredients are melted, add Mg-30Nd master alloy, raise the temperature to 720°C and continue smelting for 30 minutes, stir twice to make the melt uniform, and continue to add protective gas protection at the same time. Cool down to 700°C and stand still for 20 minutes to allow the inclusions to settle, skim off the scum on the surface of the melt, and then cast it into an ingot, and use a lathe to further cut the ingot into a cylindrical extrusion billet with a diameter of 60mm and a length of 150mm. Place the extruded billet in a vacuum heat treatment furnace at 500°C for homogenization, water cooling, then preheat at 390°C for 2 hours, and extrude at 380°C with an extrusion ratio of 36:1 and an extrusion speed of 4m/min , using animal oil as lubricating oil to obtain magnesium alloy rods with a diameter of 10mm. Cut part of the bar and process it into a standard tensile sample of M10Φ5, three parallel samples, and test the mechanical properties of the material. The tensile strength of the alloy at room temperature is 200MPa, and the elongation at break reaches 37%.

The deformed magnesium alloy soaking test sample was prepared by wire cutting. The sample diameter was 10mm and the thickness was 3mm. The surface of the sample was polished with 2000# sandpaper until it was bright, and the soaking test was carried out in Hank's solution. The soaking ratio was 1.25ml/cm ² , and Hank's solution was replaced every day. After 3 weeks of immersion experiment, the soaked sample surface was ultrasonically cleaned with 200 g/L chromic acid solution for 3 minutes. By comparing the weight change of samples before and after immersion, the corrosion rate of magnesium alloy was calculated to be 0.09mm/year. In addition, the cytotoxicity test shows that the survival rate of the experimental cell L929 reaches 82%, which is higher than the first level standard of cytotoxicity of 75%, indicating that the material is non-toxic.

Example 2:

The composition design (weight percentage) of the alloy is: 1.0Zn, 0.5Mn, 2.0Nd, the weight percentage of the limiting impurity elements is Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg. Prepare the alloy according to the above ingredients, add preheated Mg ingot, Zn ingot, and electrolytic Mn powder into the melting furnace, and the alloy melting temperature is 700°C. After the alloy is completely melted, add Mg-30Nd master alloy, raise the temperature to 720°C and continue melting for 30 minutes, stir twice to make the melt uniform, and continue to add protective gas protection at the same time. Cool down to 700°C and stand still for 20 minutes to allow the inclusions to settle, skim off the scum on the surface of the melt, and then cast it into an ingot, and use a lathe to further cut the ingot into a cylindrical extrusion billet with a diameter of 60mm and a length of 150mm. Place the extruded billet in a vacuum heat treatment furnace at 500°C for homogenization, water cooling, then preheat at 390°C for 2 hours, and extrude at 380°C with an extrusion ratio of 36:1 and an extrusion speed of 4m/min , using animal oil as lubricating oil to obtain magnesium alloy rods with a diameter of 10mm. Cut part of the bar and process it into a standard tensile sample of M10Φ5, three parallel samples, and test the mechanical properties of the material. The tensile strength of the alloy at room temperature is 225MPa, and the elongation at break reaches 33%.

The deformed magnesium alloy soaking test sample was prepared by wire cutting. The sample diameter was 10mm and the thickness was 3mm. The surface of the sample was polished with 2000# sandpaper until it was bright, and the soaking test was carried out in Hank's solution. The soaking ratio was 1.25ml/cm ² , and Hank's solution was replaced every day. After 3 weeks of immersion experiment, the soaked sample surface was ultrasonically cleaned with 200 g/L chromic acid solution for 3 minutes. By comparing the weight change of the sample before and after immersion, the corrosion rate of the magnesium alloy was calculated to be 0.15mm/year. In addition, the cytotoxicity test shows that the survival rate of the experimental cell L929 reaches 83%, which is higher than the first level standard of cytotoxicity of 75%, indicating that the material is non-toxic.

Example 3:

The composition design (weight percentage) of the alloy is: 2.0Zn, 0.5Mn, 2.0Nd, the weight percentage of the limiting impurity elements is Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg. Prepare the alloy according to the above ingredients, add preheated Mg ingot, Zn ingot, and electrolytic Mn powder into the melting furnace, and the alloy melting temperature is 700°C. After the alloy is completely melted, add Mg-30Nd master alloy, raise the temperature to 720°C and continue melting for 30 minutes, stir twice to make the melt uniform, and continue to add protective gas protection at the same time. Cool down to 700°C and stand still for 20 minutes to allow the inclusions to settle, skim off the scum on the surface of the melt, and then cast it into an ingot, and use a lathe to further cut the ingot into a cylindrical extrusion billet with a diameter of 60mm and a length of 150mm. Place the extruded billet in a vacuum heat treatment furnace at 500°C for homogenization, water cooling, then preheat at 390°C for 2 hours, and extrude at 380°C with an extrusion ratio of 36:1 and an extrusion speed of 4m/min , using animal oil as lubricating oil to obtain magnesium alloy rods with a diameter of 10mm. Cut part of the bar and process it into a standard tensile sample of M10Φ5, three parallel samples, and test the mechanical properties of the material. The tensile strength of the alloy at room temperature is 240MPa, and the elongation at break reaches 35%.

The deformed magnesium alloy soaking test sample was prepared by wire cutting. The sample diameter was 10mm and the thickness was 3mm. The surface of the sample was polished with 2000# sandpaper until it was bright, and the soaking test was carried out in Hank's solution. The soaking ratio was 1.25ml/cm ² , and Hank's solution was replaced every day. After 3 weeks of immersion experiment, 200g/L chromic acid solution was used to ultrasonically clean the soaked sample surface for 3 minutes. By comparing the weight change of the sample before and after immersion, the corrosion rate of the magnesium alloy was calculated to be 0.21mm/year. In addition, the cytotoxicity test shows that the survival rate of the experimental cell L929 reaches 82%, which is higher than the first level standard of cytotoxicity of 75%, indicating that the material is non-toxic.

Example 4:

The composition design (percentage by weight) of the magnesium alloy is: 4.0Zn, 0.5Mn, 2.0Nd, the weight percent of the restricted impurity elements is Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg. Prepare the alloy according to the above ingredients, add preheated Mg ingot, Zn ingot, and electrolytic Mn powder into the melting furnace, and the alloy melting temperature is 700°C. After all the ingredients are melted, add Mg-30Nd master alloy, raise the temperature to 720°C and continue smelting for 30 minutes, stir twice to make the melt uniform, and continue to add protective gas protection at the same time. Cool down to 700°C and stand still for 20 minutes to allow the inclusions to settle, skim off the scum on the surface of the melt, and then cast it into an ingot, and use a lathe to further cut the ingot into a cylindrical extrusion billet with a diameter of 60mm and a length of 150mm. Place the extruded billet in a vacuum heat treatment furnace at 500°C for homogenization, water cooling, then preheat at 390°C for 2 hours, and extrude at 380°C with an extrusion ratio of 36:1 and an extrusion speed of 4m/min , using animal oil as lubricating oil to obtain magnesium alloy rods with a diameter of 10mm. Cut part of the bar and process it into a standard tensile sample of M10Φ5, three parallel samples, and test the mechanical properties of the material. The tensile strength of the alloy at room temperature is 260MPa, and the elongation at break reaches 30%.

The deformed magnesium alloy soaking test sample was prepared by wire cutting. The sample diameter was 10mm and the thickness was 3mm. The surface of the sample was polished with 2000# sandpaper until it was bright, and the soaking test was carried out in Hank's solution. The soaking ratio was 1.25ml/cm ² , and Hank's solution was replaced every day. After 3 weeks of immersion experiment, the soaked sample surface was ultrasonically cleaned with 200 g/L chromic acid solution for 3 minutes. By comparing the weight changes of the samples before and after immersion, the corrosion rate of the magnesium alloy was calculated to be 0.25mm/year. In addition, the cytotoxicity test shows that the survival rate of the experimental cell L929 reaches 84%, which is higher than the first level standard of cytotoxicity of 75%, indicating that the material is non-toxic.

Example 5:

The composition design (percentage by weight) of the magnesium alloy is: 2Zn, 0.5Mn, 0.5Nd, the weight percent of the restricted impurity elements is Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg. Prepare the alloy according to the above ingredients, add preheated Mg ingot, Zn ingot, and electrolytic Mn powder into the melting furnace, and the alloy melting temperature is 700°C. After all the ingredients are melted, add Mg-30Nd master alloy, raise the temperature to 720°C and continue smelting for 30 minutes, stir twice to make the melt uniform, and continue to add protective gas protection at the same time. Cool down to 700°C and stand still for 20 minutes to allow the inclusions to settle, skim off the scum on the surface of the melt, and then cast it into an ingot, and use a lathe to further cut the ingot into a cylindrical extrusion billet with a diameter of 60mm and a length of 150mm. Place the extruded billet in a vacuum heat treatment furnace at 500°C for homogenization, water cooling, then preheat at 390°C for 2 hours, and extrude at 380°C with an extrusion ratio of 36:1 and an extrusion speed of 4m/min , using animal oil as lubricating oil to obtain magnesium alloy rods with a diameter of 10mm. Cut part of the bar and process it into a standard tensile sample of M10Φ5, three parallel samples, and test the mechanical properties of the material. The tensile strength of the alloy at room temperature is 230MPa, and the elongation at break reaches 25%.

The deformed magnesium alloy soaking test sample was prepared by wire cutting. The sample diameter was 10mm and the thickness was 3mm. The surface of the sample was polished with 2000# sandpaper until it was bright, and the soaking test was carried out in Hank's solution. The soaking ratio was 1.25ml/cm ² , and Hank's solution was replaced every day. After 3 weeks of immersion experiment, the soaked sample surface was ultrasonically cleaned with 200 g/L chromic acid solution for 3 minutes. By comparing the weight change of samples before and after immersion, the corrosion rate of magnesium alloy was calculated to be 0.06mm/year. In addition, the cytotoxicity test shows that the survival rate of the experimental cell L929 reaches 88%, which is higher than the first level standard of cytotoxicity of 75%, indicating that the material is non-toxic.

Embodiment 6:

The composition design (percentage by weight) of the magnesium alloy is: 4.0Zn, 0.5Mn, 0.5Nd, the weight percent of the restricted impurity elements is Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg. Prepare the alloy according to the above ingredients, add preheated Mg ingot, Zn ingot, and electrolytic Mn powder into the melting furnace, and the alloy melting temperature is 700°C. After all the ingredients are melted, add Mg-30Nd master alloy, raise the temperature to 720°C and continue smelting for 30 minutes, stir twice to make the melt uniform, and continue to add protective gas protection at the same time. Cool down to 700°C and stand still for 20 minutes to allow the inclusions to settle, skim off the scum on the surface of the melt, and then cast it into an ingot, and use a lathe to further cut the ingot into a cylindrical extrusion billet with a diameter of 60mm and a length of 150mm. Place the extruded billet in a vacuum heat treatment furnace at 500°C for homogenization, water cooling, then preheat at 390°C for 2 hours, and extrude at 380°C with an extrusion ratio of 36:1 and an extrusion speed of 4m/min , using animal oil as lubricating oil to obtain magnesium alloy rods with a diameter of 10mm. Cut part of the bar and process it into a standard tensile sample of M10Φ5, three parallel samples, and test the mechanical properties of the material. The tensile strength of the alloy at room temperature is 270MPa, and the elongation at break reaches 23%.

Prepare deformed magnesium alloy immersion test samples by wire cutting, sample diameter 10mm, thickness 3mm, use 2000# sandpaper to grind the sample surface until bright, conduct immersion experiments in Hank's solution, immersion ratio 1.25ml/cm ² , replace Hank's solution every day, After 3 weeks of immersion experiment, the soaked sample surface was ultrasonically cleaned with 200 g/L chromic acid solution for 3 minutes. By comparing the weight changes of the samples before and after immersion, the corrosion rate of the magnesium alloy was calculated to be 0.12mm/year. In addition, the cytotoxicity test shows that the survival rate of the experimental cell L929 reaches 86%, which is higher than the first level standard of cytotoxicity of 75%, indicating that the material is non-toxic.

Embodiment 7:

The composition design (percentage by weight) of the magnesium alloy is: 6.0Zn, 0.5Mn, 0.5Nd, the weight percent of the restricted impurity elements is Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg. Prepare the alloy according to the above ingredients, add preheated Mg ingot, Zn ingot, and electrolytic Mn powder into the melting furnace, and the alloy melting temperature is 700°C. After all the ingredients are melted, add Mg-30Nd master alloy, raise the temperature to 720°C and continue smelting for 30 minutes, stir twice to make the melt uniform, and continue to add protective gas protection at the same time. Cool down to 700°C and stand still for 20 minutes to allow the inclusions to settle, skim off the scum on the surface of the melt, and then cast it into an ingot, and use a lathe to further cut the ingot into a cylindrical extrusion billet with a diameter of 60mm and a length of 150mm. Place the extruded billet in a vacuum heat treatment furnace at 500°C for homogenization, water cooling, then preheat at 390°C for 2 hours, and extrude at 380°C with an extrusion ratio of 36:1 and an extrusion speed of 4m/min , using animal oil as lubricating oil to obtain magnesium alloy rods with a diameter of 10mm. Cut part of the bar and process it into a standard tensile sample of M10Φ5, three parallel samples, and test the mechanical properties of the material. The tensile strength of the alloy at room temperature is 300MPa, and the elongation at break reaches 20%.

The deformed magnesium alloy soaking test sample was prepared by wire cutting. The sample diameter was 10mm and the thickness was 3mm. The surface of the sample was polished with 2000# sandpaper until it was bright, and the soaking test was carried out in Hank's solution. The soaking ratio was 1.25ml/cm ² , and Hank's solution was replaced every day. After 3 weeks of immersion experiment, the soaked sample surface was ultrasonically cleaned with 200 g/L chromic acid solution for 3 minutes. By comparing the weight change of the sample before and after immersion, the corrosion rate of the magnesium alloy was calculated to be 0.35mm/year. In addition, the cytotoxicity test shows that the survival rate of the experimental cell L929 reaches 81%, which is higher than the first level standard of cytotoxicity of 75%, indicating that the material is non-toxic.

Claims (9)

1. A high-strength and high-plasticity medical magnesium alloy, characterized in that: by weight percentage, the magnesium alloy chemical composition is: Zn0.2-6.0%, Nd0.5-2.0%, Mn0.5%, limit the content of impurity elements It is: Fe<0.006%, Cu<0.005%, Ni<0.006%, and the rest is Mg. 2. The preparation process of high-strength and high-plasticity medical magnesium alloy according to claim 1, characterized in that: by weight percentage, the Mn content in the magnesium alloy is 0.5%. 3. The preparation process of high-strength and high-plasticity medical magnesium alloy according to claim 1, characterized in that: the process comprises the steps of: (1) Homogenization treatment: The magnesium alloy ingot is subjected to homogenization heat treatment at 400-550°C for 10 hours in a vacuum heat treatment furnace to homogenize the composition and structure of the ingot, and then water-cooled to form a supersaturated solid solution ; (2) Extrusion treatment: before extrusion, the ingot is preheated in a furnace at 390°C for 2 hours, and then extruded at 380°C with an extrusion ratio of 36:1 and an extrusion speed of 4m/min, so as to obtain the medical magnesium alloy. 4. The preparation process of high-strength and high-plasticity medical magnesium alloy according to claim 3, characterized in that: in step (2) extrusion process, animal oil is used as lubricating oil. 5. The preparation process of high-strength and high-plasticity medical magnesium alloy according to claim 3, characterized in that: the preparation steps of the magnesium alloy ingot in step (1) are as follows: (a) Ingredients: According to the required composition design, first carry out the ingredients, including Mg ingots with a purity of 99.99%, Zn ingots with a purity of 99.99%, Mg-30Nd master alloys with a purity of 99.99%, and electrolytic Mn powder; (b) Alloy smelting and casting: add preheated Mg ingot, Zn ingot, and electrolytic Mn powder into the melting furnace, and the alloy melting temperature is 700°C; Continue to smelt for 30 minutes at a temperature of 720°C, stir twice to make the melt uniform; cool down to 700°C and let stand for 15-30 minutes to allow the inclusions to settle, then skim off the surface scum and cast it into a graphite mold to obtain high purity Degree of medical magnesium alloy ingot. 6. The preparation process of high-strength and high-plasticity medical magnesium alloy according to claim 5, characterized in that: during the alloy melting process, the protective gas is continuously introduced. 7. The preparation process of high-strength and high-plasticity medical magnesium alloy according to claim 5, characterized in that: the graphite mold is slightly bell-mouthed to prevent the occurrence of larger shrinkage cavities. 8. The preparation process of high-strength and high-plasticity medical magnesium alloy according to claim 1, characterized in that: the magnesium alloy is used as a degradable metal implant material. 9. The preparation process of high-strength and high-plasticity medical magnesium alloy according to claim 8, characterized in that: the magnesium alloy is used as degradable cardiovascular stent material, degradable suture material, degradable bone nail, bone plate or Bone filling materials, etc.