CN102978495A - Mg-Sr-Zn alloy and preparation method thereof - Google Patents

Abstract

The invention discloses a Mg-Sr-Zn alloy and a preparation method thereof. The alloy includes Mg, Sr and Zn; by weight percentage, in the medical implant, the content of Sr is 0-5%, but not zero, and the content of Zn is 0-2%, but not zero , the balance being Mg. Mix the Mg, Sr, Zn and trace elements according to any of the following 1) to 2) to obtain a mixture: 1) Mg, Sr and Zn; and 2) Mg, Sr, Zn and trace elements; in Under the protection of CO ₂ and SF ₆ atmosphere, the mixture is melted to obtain the alloy. The degradable and absorbable Mg-Sr-Zn series magnesium alloy of the present invention uses essential metal elements for the human body and does not contain harmful or potentially harmful elements. The alloying element Sr in it can promote bone formation and inhibit bone resorption, thereby accompanying Mg-Sr- Degradation of Zn-based alloys promotes tissue healing.

Description

A kind of Mg-Sr-Zn alloy and its preparation method

technical field

The invention relates to a Mg-Sr-Zn alloy and a preparation method thereof, belonging to the field of medical metal materials.

Background technique

At present, medical biodegradable materials are mainly degradable polymer materials and degradable ceramic materials. Degradable polymer materials include polyglycolic acid (PGA), polylactic acid (PLA), polylactone (PCL) and their copolymers, natural polysaccharide materials (cellulose, chitin) and natural protein materials (collagen, Fibrin), etc., although this material can be completely absorbed by the human body, its strength is low, it is difficult to provide structural support, and its degradation products in the body can easily cause inflammatory reactions and other problems. Degradable ceramic materials include hydroxyapatite, α-tricalcium phosphate, β-tricalcium phosphate, and tetracalcium oxyphosphate, but this material has poor toughness and cannot coordinate deformation.

Biomedical metal materials are widely used in the field of medical devices due to their excellent mechanical properties, biocompatibility and corrosion resistance. At present, biomedical metal materials are mainly 316L, 317L, 304V stainless steel, Co-Cr-Mo alloy, pure titanium, Ti-6Al-4V, TiNi alloy, etc. The main disadvantage is that it is not degradable, and it will be permanently "alien" in the body. form exists. At the same time, the mechanical properties of stainless steel, Co-Cr-Mo alloy and titanium alloy, especially the elastic modulus, do not match the bone tissue. For example, the elastic modulus of stainless steel is about 200GPa, and that of titanium alloy is about 100GPa. Only 10-40GPa, so the metal implant will bear almost all the load after implantation, causing the stress shielding phenomenon of bone tissue, that is, the bone tissue around the implant shrinks or loosens.

Contents of the invention

The purpose of the present invention is to provide a Mg-Sr-Zn alloy and its preparation method. The medical implant provided by the present invention is a biodegradable, absorbable, mechanically compatible with bone tissue, biocompatible and corrosion resistant. Good degradable and absorbable Mg-Sr-Zn alloy medical implant.

A Mg-Sr-Zn alloy provided by the present invention includes Mg, Sr and Zn;

In terms of weight percentage, in the alloy, the content of Sr is 0-5%, but not zero, and the content of Zn is 0-2%, but not zero. The alloy provided by the present invention can be dense structure or porous structure .

In the above alloy, the alloy further includes trace elements, and the trace elements may specifically be at least one of manganese, zirconium, tin, rare earth and yttrium;

In the alloy, the mass percentage of the trace elements may be 0-2%, but not zero.

In the above alloy, in the alloy, the mass percentage of manganese is not more than 1.5%, the mass percentage of zirconium is not more than 1%, the mass percentage of tin is not more than 2%, and the mass percentage of rare earth is not more than 1.5%. More than 2%, and the mass percentage of yttrium is not more than 1%.

In the above alloy, the surface of the alloy is further coated with a degradable polymer coating or a degradable ceramic coating.

The concrete composition in above-mentioned alloy is as follows: be made up of Mg, Sr and Zn, the mass percentage composition of Sr is 2% ~ 5%, the mass percentage composition of Zn is 1% ~ 2% and the Mg of balance, specifically can be 97% Mg, 2% Sr and 1% Zn or 93% Mg, 5% Sr and 2% Zn; composed of Mg, Sr, Zn and Sn, such as 95% Mg, 3% Sr, 1.5% Zn and 0.5% Sn.

In the above alloys, the degradable polymer coating can be polyglycolic acid (PGA), polylactic acid (PLA), L-polylactic acid (PLLA), polycaprolactone (PCL), polycyanoacrylate One or more of (PACA), polydioxanone, polyanhydride, polyphosphazene, amino acid polymers, poly-β-hydroxybutyrate and hydroxyvalerate or their copolymers mixture;

The degradable ceramic coating can be one or one of hydroxyapatite, strontium-containing hydroxyapatite, fluorine-containing hydroxyapatite, α-tricalcium phosphate, β-tricalcium phosphate and oxytetracalcium phosphate more than one mixture;

The thickness of the degradable polymer coating or the degradable ceramic coating can be 0.01-5 mm.

The present invention provides the above alloy preparation method, comprising the following steps: mixing the Mg, Sr, Zn and trace elements according to any one of the following 1) to 2) to obtain a mixture:

1) Mg, Sr and Zn; and

2) Mg, Sr, Zn and trace elements;

Under the protection of CO ₂ and SF ₆ atmosphere, the mixture is smelted to obtain the alloy with a dense structure.

In the above preparation method, the smelting temperature may be 700-850°C, and the smelting time may be 30min-4h, such as 30min at 850°C.

The Sr may be added in the form of a Mg-Sr master alloy.

In the above preparation method, the method further includes the step of machining the alloy; the machining is one or more of rolling, forging, extrusion and rapid solidification;

The rolling includes the following steps: subjecting the alloy to solution treatment, and then sequentially undergoing rough rolling, intermediate rolling and finish rolling; for example, solution treatment at 300-500°C for 2-20 hours, and then at 400-500°C Rough rolling is carried out with a pass reduction of 10~15%; intermediate rolling is carried out at 350~400°C with a pass reduction of 30~60%; finish rolling is carried out at 200~350°C with a pass reduction of 5~ 10%;

The forging temperature may be 200-400°C, the forging rate may be 200mm/s-400mm/s, and the forging rate may be 5%-15%;

The extrusion temperature may be 200-400°C, such as 270°C, the extrusion rate may be 0.1-50mm/min, such as 2mm/min, and the extrusion ratio may be 10-100, such as 25;

The rapid solidification is made of a rapid solidification thin strip under the protection of Ar gas by using a high-vacuum rapid quenching system, wherein the feeding amount is 2-8g, the induction heating power is 3-7kW, the distance between the nozzle and the roller is 0.8mm, and the injection pressure is 0.05~0.2MPa, the speed of the roller is 500~5000r/min, the size of the nozzle slit is 1film×8mm×6mm; then the thin strip is crushed into powder, and vacuum hot pressed at 200~350℃ for 1~24h to make Mg -Sr-Zn series alloy extruded blank, then extruded in the range of 200~400℃, the extrusion ratio is 10~60.

The present invention also provides another method for preparing the above-mentioned alloy, which includes the following steps: mixing the Mg, Sr, Zn and trace elements according to any of the following 1) to 2) to obtain a mixture:

1) Mg, Sr and Zn; and

2) Mg, Sr, Zn and trace elements;

Sintering the mixture, and then cooling to obtain the alloy, which is a porous structure;

The sintering is any one of the following methods: element powder mixing sintering method, pre-alloy powder sintering method and self-propagating high-temperature synthesis method.

The element powder mixing sintering method includes the following steps: sintering under the condition of an Ar gas protective atmosphere, raising the temperature to 200-500°C at a rate of 2-4°C/min, and then raising the temperature to 650°C at a rate of 30°C/min. ℃, sintering for 1 to 12 hours, and then furnace cooling to obtain a medical implant with a porous structure.

The pre-alloy powder sintering method includes the following steps: placing the mixture under the condition of 300-650° C. for heat treatment for 1-12 hours, such as heat-treating under the condition of 650° C. for 4 hours to obtain an alloy with a porous structure.

The self-propagating high-temperature synthesis method includes the following steps: under the protection of an inert gas, the gas pressure is 1×10 ³ -1×10 ⁵ Pa, and the mixture is ignited at 200-700° C. for self-propagating high-temperature synthesis to obtain an alloy with a porous structure .

In the above preparation method, the method further includes the step of coating the surface of the alloy with the degradable polymer coating or the degradable ceramic coating;

Coating the degradable polymer coating by pulling method or glue leveling method;

Coating the degradable ceramic coating by ion spraying, electrodeposition or anodic oxidation;

The thickness of the degradable polymer coating and the degradable ceramic coating may be 5-50 microns, such as 10-30 microns.

The pulling method includes the following steps: pickling the Mg-Sr-Zn alloy, and dissolving the degradable polymer coating material in an organic solvent to make a polymer material colloid, and then pickling the The Mg-Sr-Zn alloy is dip-coated in the polymer material colloid and pulled out at a uniform speed for centrifugation to obtain a degradable and absorbable Mg-Sr-Zn alloy medical implant coated with a degradable polymer coating. body. The organic solvent is preferably trichloroethane.

The colloid leveling method includes the following steps: pickling the Mg-Sr-Zn alloy, and simultaneously dissolving the material of the degradable polymer coating in an organic solvent to make a polymer material colloid, and then dissolving the polymer material The colloid is dropped on the surface of the alloy, and the colloid is spread on the alloy to form a thin layer by using the high-speed rotation of the glue homogenizer, dried to remove excess solvent, and coated several times to achieve the best effect, and the surface is coated with a degradable polymer coating. A biodegradable and absorbable Mg-Sr-Zn alloy medical implant. The organic solvent is preferably trichloroethane.

The main plasma gas used in the plasma spraying is Ar 30-100 scfh, the secondary gas is H ₂ 5-20 scfh, the spraying current is 400-800A, the spraying voltage is 40-80V, and the spraying distance is 100-500mm.

The electrodeposition is to use the Mg-Sr-Zn alloy as the cathode, in the electrolyte solution containing calcium, phosphorus, fluorine or strontium salt, the current density is 0.5~30mA/cm ² , the temperature is 25~85°C, the treatment After 10-60 minutes, wash and dry to obtain the medical implant.

The anodic oxidation method is to oxidize the Mg-Sr-Zn alloy in the electrolytic solution of calcium, phosphorus, fluorine or strontium salt at 200-500V for 5-30min.

The present invention also provides the application of the above-mentioned Mg-Sr-Zn alloy in the preparation of medical implants, such as the application in bone tissue repair brackets.

The principle that the alloy provided by the present invention can be used as a medical implant is as follows: (1) From the perspective of biocompatibility, magnesium is an essential element for the human body, so people with normal renal function use 4-6g of magnesium per day, generally not Cause toxic and side effects; From the perspective of material science, the density of magnesium alloy (1.75~1.85g/cm ³ ) is similar to that of human dense tissue (1.75g/cm ³ ), and the elastic modulus is about 45GPa, which is less than that of medical titanium alloy. 1/2 of the modulus (109-112GPa), can effectively alleviate the stress shielding effect of orthopedic implants; moreover, magnesium alloys are chemically active and can be corroded and degraded in the environment of human body fluids containing Cl-. (2) Strontium is a trace element in the human body, 99% of which exists in bones and teeth; Sr salt can promote the formation of bone tissue and inhibit bone resorption, thereby increasing bone mass and improving bone strength, and treating osteoporosis. From the perspective of materials science, adding Sr in an appropriate amount can improve the room temperature and high temperature strength of magnesium alloys, improve the high temperature creep properties and thermal cracking resistance of magnesium alloys, and improve the corrosion resistance of magnesium alloys. (3) Zinc is an essential trace element for the human body. Zinc in the body is almost exclusively in the form of Zn ²⁺ bound to cellular proteins. In metallurgy, the maximum solid solubility of zinc in magnesium is 6.2%, which has the effects of solid solution strengthening and aging strengthening, which can significantly improve the room temperature strength of magnesium alloys and improve the corrosion resistance of magnesium alloys.

Compared with the prior art, the present invention has the following advantages and effects:

(1) The degradable and absorbable Mg-Sr-Zn magnesium alloy of the present invention uses essential metal elements for the human body and does not contain harmful or potentially harmful elements. The alloying element Sr in it can promote bone formation and inhibit bone resorption, thereby accompanying Mg -Sr-Zn alloy degradation promotes tissue healing.

(2) The preparation method of the Mg-Sr-Zn series magnesium alloy of the present invention has a simple process, and through the cooperation of the composition design and the preparation process, the mechanical properties and degradation speed of the medical implant can be adjusted to obtain the best mechanical properties and Corrosion resistance.

Description of drawings

Figure 1 is the microstructure of the as-cast Mg-Sr-Zn alloy prepared in Example 1.

Fig. 2 shows the tensile properties at room temperature of the as-cast Mg-Sr-Zn alloy in Example 1 and the rolled Mg-Sr-Zn alloy prepared in Example 2.

Fig. 3 is an X-ray image of the as-rolled Mg-Sr-Zn alloy prepared in Example 2 implanted into the bone marrow cavity of a mouse for 4 weeks.

Figure 4 is a micro-CT 3D reconstruction image of the rolled Mg-Sr-Zn alloy prepared in Example 2 implanted into the bone marrow cavity of a mouse for 4 weeks.

Figure 5 is a micro-CT 2D image of the rolled Mg-Sr-Zn alloy prepared in Example 2 implanted into the bone marrow cavity of a mouse for 4 weeks.

Detailed ways

The experimental methods used in the following examples are conventional methods unless otherwise specified.

The materials and reagents used in the following examples can be obtained from commercial sources unless otherwise specified.

Embodiment 1, preparation as-cast Mg-Sr-Zn alloy and its tensile properties

The test raw materials are pure Mg (99.95wt.%), pure Zn and Mg-Sr master alloy, according to the proportion: Sr 2%, Zn 1% and the balance is Mg, and the raw materials are weighed: Mg, Mg-Sr master alloy and Zn .

Melt the pure magnesium ingot under the protection of CO ₂ and SF ₆ atmosphere, raise the temperature to 750°C, add the Mg-Sr master alloy, stir for 10 minutes after it melts, then add Zn, stir for 10 minutes to make the alloying elements Sr and Zn homogeneous . After raising the temperature to 750°C and keeping it warm for 30 minutes, the melt was poured into a mold preheated to 300°C for gravity casting to obtain a Mg-Sr-Zn ingot.

The microstructure of the as-cast Mg-Sr-Zn alloy prepared in this example is shown in Figure 1, and it can be obtained from this figure that the grain diameter of the as-cast Mg-Sr-Zn alloy prepared in this example is less than 100 μm. There is secondary phase precipitation inside the particle.

The as-cast Mg-Sr-Zn alloy prepared in this example is processed into a tensile standard sample according to the ASTM tensile standard wire cutting, and the SiC water-resistant sandpaper is polished to 2000#, and the room temperature tensile test is carried out by using a general tensile testing machine. Tensile test, the tensile speed is 1mm/min.

The room temperature tensile properties of the as-cast Mg-Sr-Zn alloy prepared in this example are shown in Figure 2 (black bar graph).

Embodiment 2, preparation rolled state Mg-Sr-Zn alloy and its tensile properties

The as-cast Mg-Sr-Zn alloy was prepared according to the steps in Example 1, and then the as-cast Mg-Sr-Zn alloy was processed into a 5mm thick plate, sanded until there were no obvious defects, and solution treated at 400°C Rolling for 3 hours: rough rolling, intermediate rolling and finish rolling in sequence: rough rolling at 450°C, with a reduction of 10% per pass, intermediate rolling at 400°C, with a reduction of 50 passes %, rough rolling is carried out at 350°C, the reduction in each pass is 10%, and finally rolled to a 2mm thick sheet.

The rolled Mg-Sr-Zn alloy prepared in this embodiment is processed into a tensile standard sample according to the ASTM tensile standard wire cutting, and the SiC water-resistant sandpaper is polished to 2000#, and the tensile test at room temperature is carried out using a general tensile testing machine. The speed is 1mm/min.

The room temperature tensile properties of the as-rolled Mg-Sr-Zn alloy prepared in this example are shown in Figure 2 (gray histogram), from which it can be known that the yield strength and tensile properties of the as-rolled Mg-Sr-Zn alloy The strength is significantly higher than that of the as-cast alloy, but the elongation at break is not much different between the two, but the elongation at break of the as-cast alloy is slightly longer.

Process the as-rolled Mg-Sr-Zn alloy prepared in this example into rods with a diameter of 0.7 mm and a length of 5 mm, grind and polish to 2000# sandpaper, and sterilize with ethylene oxide. Eight 3-month-old C57BL/6 mice were selected and randomly divided into two groups with 4 mice in each group. In one group, the left knee was anesthetized and the skin was prepared and disinfected. A 0.7mm diameter hole was drilled in the distal femur, and an alloy rod was implanted in the hole and sutured. Another group of mice was drilled in the left femur as a blank control. Periodic observation after the operation did not reveal foreign body reactions such as inflammation of the surrounding tissue caused by the implant. After 4 weeks, it was found that the osteogenesis was significantly reversed, the density of trabecular bone was higher than that of the control group, and the osteogenesis of the outer periosteum and inner periosteum were higher than that of the control group.

The X-ray and micro-CT observation results of the rolled Mg-Sr-Zn alloy obtained in this embodiment were implanted into the bone marrow cavity of mice for 4 weeks, as shown in Figure 3, Figure 4 and Figure 5, and can be known from these results , 4 weeks after being implanted into the bone marrow cavity of mice, the alloy implants had been partially degraded, and new bone was formed at the degraded sites.

Example 3, Preparation of Extruded Mg-Sr-Zn-Sn Alloy and Its Biocompatibility and Degradability

The test raw materials are pure Mg (99.95wt.%), Mg-Sr master alloy, pure Zn and pure Sn, according to the proportion: Sr 3%, Zn 1.5%, Sn 0.5% and the balance is Mg, and the raw materials are weighed: Mg, Mg-Sr master alloy, Zn and Sn.

Melt the pure magnesium ingot under the protection of CO ₂ and SF ₆ atmosphere, raise the temperature to 750°C, add the Mg-Sr master alloy, stir for 10 min after it melts, then add Zn and Sn, and stir for 10 min to make the alloying elements Sr, Zn and Sn homogenization. After raising the temperature to 750°C and keeping it warm for 30 minutes, pour the melt into a mold preheated to 300°C for gravity casting to obtain a Mg-Sr-Zn-Sn ingot. The prepared ingot was kept at 400° C. for 3 hours, and then extruded at an extrusion rate of 2 mm/min, an extrusion ratio of 25:1, and an extrusion temperature of 270° C.

The extruded Mg-Sr-Zn-Sn alloy prepared by the above method was processed into screws and implanted into the left femurs of 18 New Zealand white rabbits, and pure Ti screws were implanted on the opposite side. The experimental animals were sacrificed at 1 month, 6 months and 12 months after operation. No foreign body reaction such as inflammation of the surrounding tissue caused by the implant was found in 18 rabbits. The volume of the Mg-Sr-Zn-Sn alloy implant at 12 months after operation The reduction was 58%, and the degraded parts were filled with new bone.

Example 4. Preparation of Mg-Sr-Zn alloy with porous structure and its bone tissue matching properties

Mix pure Mg (purity 99.95%), pure Sr (purity 99.9%) and pure Zn (purity 99.999%) in a mass ratio of 93:5:2, mix them evenly, press them into billets, and heat them in a vacuum sintering furnace (VSF series (general-purpose) vacuum sintering furnace, Shenyang Vacuum Technology Research Institute), the specific sintering steps are: after slowly heating up to 300°C at 2°C/min, then rapidly raising the temperature to 650°C at 30°C/min , and then kept at this temperature for 4h, and finally, the furnace was cooled, and the porous structure of Mg-Sr-Zn alloy was obtained by pre-alloy powder sintering method.

The porosity was measured to be 50% by the drainage method, and the porous Mg-Sr-Zn alloy was cut into a cube with a size of 5×5×5 mm ³ to obtain a medical implant-bone tissue repair scaffold.

手钻在家兔股骨处钻孔后将植入体埋植入左侧股骨，术后注射青霉素钾15mg/kg，实验以316L不锈钢（西北有色金属研究院）支架作为对照；术后1个、5个月分别处死实验动物。术后1个月，micro-CT观察家兔股骨处该合金材料由于腐蚀降解体积逐步减小，材料周围的骨组织修复受损骨且接触紧密。骨组织修复支架植入体植入5月后，均完全降解，而316L不锈钢支架周围组织发炎。Twelve bone tissue repair scaffold implants prepared according to the above method were respectively implanted in the femurs of 12 rabbits by surgery.

After drilling a hole in the femur of a rabbit with a hand drill, the implant was embedded in the left femur, and 15 mg/kg of penicillin potassium was injected after the operation. The 316L stainless steel (Northwest Nonferrous Metals Research Institute) stent was used as a control in the experiment; The experimental animals were sacrificed at 5 months respectively. One month after operation, micro-CT observed that the volume of the alloy material at the femur of the rabbit gradually decreased due to corrosion degradation, and the bone tissue around the material repaired the damaged bone and was in close contact. Five months after implantation of the bone tissue repair stent implants, they were completely degraded, while the surrounding tissues of the 316L stainless steel stents were inflamed.

Example 5. Preparation and degradability of as-rolled Mg-Sr-Zn alloy coated with L-polylactic acid (PLLA) on the surface

Prepare the rolled Mg-Sr-Zn alloy according to the method in Example 2, and then coat the PLLA coating on its surface according to the following pulling method, with a thickness of 10-30 μm, to prepare the PLLA surface modified bone fixation plate:

(1) Use concentrated nitric acid and hydrofluoric acid to prepare pickling solution, and pickle the bone fixation plate for 5-20 minutes.

(2) Dissolve 0.5g PLLA (molecular weight: 80~200kDa) in 10ml trichloroethane.

(3) Soak the pickled alloy implant in the colloid for 30 minutes, pull it out at a constant speed, and dry it overnight in vacuum at room temperature.

(4) Disinfect and prepare for use.

The prepared PLLA surface modified Mg-Sr-Zn bone fixation plate was fixed in the femur of dogs. No foreign body reaction such as inflammation of the surrounding tissue caused by the implant was found through regular observation. It was observed that with the prolongation of implantation time, PLLA gradually dissolved, the size of the bone fixation plate became smaller, and it was closely connected with the connecting bone. After 7 months, the implanted bone fixation plate degraded completely.

Embodiment 6, the preparation and degradable property of the rolling state Mg-Sr-Zn alloy of surface coating calcium phosphorus coating

Prepare the rolled Mg-Sr-Zn alloy-bone fixation plate according to the method in Example 2, polish the bone fixation plate with 800#, 1500# and 2000# sandpaper, then apply calcium phosphorus on its surface according to the anodic oxidation method, the thickness 10~30μm: use 0.04M β-sodium glycerophosphate and 0.2M calcium acetate as the electrolyte:

(1) The bone fixation plate was anodized at 350V for 10 minutes in pH: 10~11 electrolyte.

(2) After cleaning, place the sample in a high-pressure reactor at 130°C for 4 hours.

(3) Disinfect and prepare for use.

The as-prepared anodized and hydrothermally synthesized co-surface modified bone fixation plates were fixed in dog femurs. No foreign body reaction such as inflammation of the surrounding tissue caused by the implant was found through regular observation. It was observed that as the implantation time prolongs, the surface coating gradually fuses with the bone, and the size of the bone fixation plate becomes smaller. After 12 months, the implanted bone fixation plate degraded completely.

Claims (10)

1. A Mg-Sr-Zn alloy, characterized in that: said alloy comprises Mg, Sr and Zn; In terms of weight percentage, in the alloy, the content of Sr is 0-5%, but not zero, and the content of Zn is 0-2%, but not zero. 2. The alloy according to claim 1, characterized in that: the alloy further comprises trace elements, and the trace elements are at least one of manganese, zirconium, tin, rare earth and yttrium; In the alloy, the mass percentage of the trace elements is 0-2%, but not zero. 3. The alloy according to claim 2, characterized in that: in the alloy, the mass percentage of manganese is not more than 1.5%, the mass percentage of zirconium is not more than 1%, and the mass percentage of tin is not more than 2%, the mass percentage of rare earth is not more than 2%, and the mass percentage of yttrium is not more than 1%. 4. The alloy according to any one of claims 1-3, characterized in that: the surface of the alloy is also coated with a degradable polymer coating or a degradable ceramic coating. 5. The alloy of claim 4, characterized in that: The degradable polymer coating is polyglycolic acid, polylactic acid, L-polylactic acid, polycaprolactone, polycyanoacrylate, polydioxanone, polyanhydride, polyphosphazene, One or more mixtures of amino acid polymers, poly-β-hydroxybutyrate and hydroxyvalerate or their copolymers; The degradable ceramic coating is one or one of hydroxyapatite, strontium-containing hydroxyapatite, fluorine-containing hydroxyapatite, α-tricalcium phosphate, β-tricalcium phosphate and tetracalcium oxyphosphate the above mixture; The thickness of the degradable polymer coating or the degradable ceramic coating is 0.01-5mm. 6. The method for preparing the alloy according to any one of claims 1-5, comprising the steps of: mixing the Mg, Sr, Zn and trace elements according to any one of the following 1) to 2) to obtain mixture: 1) Mg, Sr and Zn; and 2) Mg, Sr, Zn and trace elements; Under the protection of CO ₂ and SF ₆ atmosphere, the mixture is melted to obtain the alloy. 7. The method according to claim 6, characterized in that: the melting temperature is 700-850°C, and the melting time is 30min-4h. The Sr is added in the form of Mg-Sr master alloy. 8. The method according to claim 6 or 7, characterized in that: the method further comprises the step of machining the alloy; the machining is one of rolling, forging, extrusion and rapid solidification one or more processing methods; The rolling includes the steps of: subjecting the alloy to solution treatment, and then sequentially undergoing rough rolling, intermediate rolling and finish rolling; The forging temperature is 200-400°C, the forging rate is 200mm/s-400mm/s, and the forging rate is 5%-15%; The extrusion temperature is 200-400° C., the extrusion rate is 0.1-30 mm/min, and the extrusion ratio is 10-100. 9. The method for preparing the alloy according to any one of claims 1-5, comprising the steps of: mixing the Mg, Sr, Zn and trace elements according to any one of the following 1) to 2) to obtain mixture: 1) Mg, Sr and Zn; and 2) Mg, Sr, Zn and trace elements; The mixture is sintered and then cooled to obtain an alloy; The sintering is any one of the following methods: element powder mixing sintering method, pre-alloy powder sintering method and self-propagating high-temperature synthesis method. 10. The application of the Mg-Sr-Zn alloy described in any one of claims 1-5 in the preparation of medical implants.

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