Degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use and preparation method therefor

Abstract

The present disclosure provides a degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use and the preparation method therefor. With regard to a total weight of the magnesium alloy of 100%, the composition of components of the magnesium alloy comprises: 1.0 to 4.5% of Nd, 0.2 to 2.0% of Zn, 0 to 1.0% of Ca, 0 to 1.0% of Zr, and balance of Mg. The magnesium alloy is prepared by producing a magnesium alloy ingot by means of vacuum semi-continuous casting and according to the components and weight percentage thereof followed by solid solution treatment and extrusion. The degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use provided by the present disclosure has the advantages of being non-toxic and fully degradable, good corrosion resistance as well as high strength and ductility etc., and can be used for preparing a vascular stent.

Claims

1. A degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use, wherein the composition of components of the magnesium alloy consists of 1.5 to 2.5% of Nd, 0.4 to 0.8% of Zn, 0.4 to 0.6% of Ca, 0.4 to 0.8% of Zr, and balance of Mg, with regard to a total weight of the magnesium alloy of 100%.

2. The degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use according to claim 1, which is prepared by at least the step of: preparing a magnesium alloy ingot by means of vacuum semi-continuous casting and according to the components and weight percentage in the degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use, wherein the raw materials used comprise at least: pure Zn, a Mg—Nd master alloy, and pure magnesium.

3. The degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use according to claim 2, wherein the raw materials used further comprise pure Ca and/or a Mg—Zr master alloy.

4. The degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use according to claim 3, wherein the pure Ca used has a purity of 99.99 wt % or more, and the Mg—Zr master alloy used is a Mg—30 wt % Zr master alloy.

5. The degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use according to claim 2, wherein the pure Zn used has a purity of 99.99 wt % or more, the Mg—Nd master alloy used is a Mg-30 wt % Nd master alloy, and the pure magnesium used has a purity of 99.99 wt % or more.

6. The degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use according to claim 2, wherein the resultant magnesium alloy ingot has a size of Φ110 to 150 mm in diameter and 2200 to 2600 mm in length.

7. The degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use according to claim 2, wherein the preparation of the degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use further comprises: cutting the resultant magnesium alloy ingot to a certain length, and subjecting it to solid solution treatment before extruding, so as to obtain the degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use.

8. The degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use according to claim 7, wherein the temperature for the solid solution treatment is 480 to 540° C., the duration of the solid solution treatment is 8 to 12 hours, the extrusion is performed at an extruding ratio of 5 to 30 in an environment at 280 to 420° C., and the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use is obtained after the extrusion as a round rod with a diameter of Φ20 to 40 mm.

9. A preparation method for the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use according to claim 1, comprising at least the step of: preparing a magnesium alloy ingot by means of vacuum semi-continuous casting and according to the components and weight percentage in the degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use, wherein the raw materials used comprise at least: pure Zn, a Mg—Nd master alloy, and pure magnesium.

10. The preparation method according to claim 9, wherein the raw materials used further comprise pure Ca and/or a Mg—Zr master alloy.

11. The preparation method according to claim 10, wherein the pure Ca used has a purity of 99.99 wt % or more, and the Mg—Zr master alloy used is a Mg-30 wt % Zr master alloy.

12. The preparation method according to claim 9, wherein the pure Zn used has a purity of 99.99 wt % or more, the Mg—Nd master alloy used is a Mg-30 wt % Nd master alloy, and the pure magnesium used has a purity of 99.99 wt % or more.

13. The preparation method according to claim 9, wherein the vacuum semi-continuous casting comprises the following steps: (1) the raw materials are melted in a vacuum melting furnace with a melt temperature controlled at 740 to 760° C. during melting, and after the raw materials are completely melted, an inert gas is introduced for stirring by gas in a vacuum environment with a stirring time of 30 to 45 min; (2) after the stirring is completed, a mixed gas of SF.sub.6 and CO.sub.2 is introduced to the surface of the melt for protection while the temperature of the melt is raised to 760 to 780° C. and kept for 30 to 40 min, and then the temperature of the melt is lowered to 700 to 720° C. and the melt is allowed to stand for 90 to 120 min; (3) casting is then carried out on a semi-continuous casting machine; during the semi-continuous casting process, a gas mixture of SF.sub.6 and CO.sub.2 is used for protection, the temperature of the melt in the vacuum melting furnace is controlled at 700 to 720° C., with the temperature of the melt in a crystallizer at 680 to 690° C. and a speed of ingot-drawing of 30 to 50 mm/min, and pressure water-cooling is applied at 300 to 500 mm close to the crystallizer while air-cooling is applied at a lower region, thereby obtaining the magnesium alloy ingot.

14. The preparation method according to claim 9, wherein the resultant magnesium alloy ingot has a size of Φ110 to 150 mm in diameter and 2200 to 2600 mm in length.

15. The preparation method according to claim 9, further comprising the following steps: cutting the obtained magnesium alloy ingot to a certain length, and subjecting it to solid solution treatment before extruding, so as to obtain the degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use.

16. The preparation method according to claim 15, wherein the temperature for the solid solution treatment is 480 to 540° C., the duration of the solid solution treatment is 8 to 12 hours, the extrusion is performed at an extruding ratio of 5 to 30 in an environment at 280 to 420° C., and the degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use is obtained after the extrusion as a round rod with a diameter of Φ20 to 40 mm.

17. A degradable corrosion-resistant strength and ductility magnesium alloy for biomedical use, wherein the composition of components of the magnesium alloy consist of 1.5 to 2.5% of Nd, 0.4 to 0.8% of Zn, 0.4 to 0.6% of Ca, 0.4 to 0.8% of Zr, inclusion elements other than Mg, Nd, Zn, Ca, and Zr, and balance of Mg, and the total amount of inclusion elements other than Mg, Nd, Zn, Ca, and Zr contained in the magnesium alloy is 0.05% or less, with regard to a total weight of the magnesium alloy of 100%.

Description

DETAILED DESCRIPTION

(1) For clearer understanding of the technical features, objects, and advantages of the present disclosure, the technical solutions of the present disclosure will be described in detail below, but it should not be construed as limiting to the scope of the present disclosure.

Example 1

(2) This example provides a degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use. The composition of the magnesium alloy comprises, with regard to a total weight of the magnesium alloy of 100%, 1.5% of Nd, 0.4% of Zn, 0.4% of Ca, 0.4% of Zr, and balance of Mg.

(3) The magnesium alloy was prepared by the following steps:

(4) (1) In a vacuum melting furnace, pure magnesium having a purity of 99.99 wt % or more, pure Zn having a purity of 99.99 wt % or more, pure Ca having a purity of 99.99 wt % or more, a Mg-30 wt % Nd master alloy and a Mg-30 wt % Zr master alloy were successively melted, and the melt temperature during melting was controlled at 740 to 760° C. After the raw materials were completely melted, argon gas was introduced to conduct gas stirring in a vacuum environment with a stirring time of 40 min.

(5) (2) After the stirring was completed, a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) was introduced to the surface of the melt for protection, and at the same time, the temperature of the melt was raised to 760 to 780° C. and kept for 30 min. After the high temperature insulation, the melting furnace was powered off, and the temperature of the melt was controlled at 700 to 720° C. and the melt was allowed to stand for 90 min.

(6) (3) Subsequently, a copper crystallizer was used for the ingot casting on a semi-continuous casting machine. The magnesium alloy melt was introduced into a diverter plate placed in the core of the inner sleeve of the crystallizer, and was diverted by the diverter plate into the space formed by the metal inner sleeve and the dummy bar of the crystallizer. At the same time, the protective gas ring was opened to provide a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) to the alloy melt for protection. During the semi-continuous casting process, the temperature of the melt in the vacuum melting furnace was controlled at 700 to 720° C., the temperature of the melt in the crystallizer was 680 to 690° C., and the speed of ingot-drawing was 40 mm/min. High pressure water-cooling was applied at 400 mm close to the crystallizer, and air-cooling was applied at a lower region.

(7) (4) The Mg—Nd—Zn—Ca—Zr magnesium alloy semi-continuous ingot obtained from the casting had a size of Φ120×2400 mm. The ingot had an appearance free of cracks and shrinkage, with a smooth and clean surface, fine and uniform structures, and no solute segregation.

(8) (5) The resultant Mg—Nd—Zn—Ca—Zr magnesium alloy ingot was cut to a certain length, subjected to solid solution treatment at 520° C. for 10 hours, and then extruded at 330° C. to form a round rod having a diameter of Φ25 mm, and thus the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use was obtained.

(9) The degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use had a tensile strength of 246 MPa, a yield strength of 207 MPa and an elongation of 34%, as well as good plasticity and mechanical properties. The corrosion rate of the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use in artificial plasma was 0.26 mm/year, in a uniform corrosion manner. Biological test results showed that the material had no obvious cytotoxicity and good blood compatibility, which met the requirements for intravascular stent materials.

Example 2

(10) This example provides a degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use. The composition of the magnesium alloy comprises, with regard to a total weight of the magnesium alloy of 100%, 2.0% of Nd, 0.6% of Zn, 0.5% of Ca, 0.6% of Zr, and balance of Mg.

(11) The magnesium alloy was prepared by the following steps:

(12) (1) In a vacuum melting furnace, pure magnesium having a purity of 99.99 wt % or more, pure Zn having a purity of 99.99 wt % or more, pure Ca having a purity of 99.99 wt % or more, a Mg-30 wt % Nd master alloy and a Mg-30 wt % Zr master alloy were successively melted, and the melt temperature during melting was controlled at 740 to 760° C. After the raw materials were completely melted, argon gas was introduced to conduct gas stirring in a vacuum environment with a stirring time of 40 min.

(13) (2) After the stirring was completed, a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) was introduced to the surface of the melt for protection, and at the same time, the temperature of the melt was raised to 760 to 780° C. and kept for 30 min. After the high temperature insulation, the melting furnace was powered off, and the temperature of the melt was controlled at 700 to 720° C. and the melt was allowed to stand for 90 min.

(14) (3) Subsequently, a copper crystallizer was used for the ingot casting on a semi-continuous casting machine. The magnesium alloy melt was introduced into a diverter plate placed in the core of the inner sleeve of the crystallizer, and was diverted by the diverter plate into the space formed by the metal inner sleeve and the dummy bar of the crystallizer. At the same time, the protective gas ring was opened to provide a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) to the alloy melt for protection. During the semi-continuous casting process, the temperature of the melt in the vacuum melting furnace was controlled at 700 to 720° C., the temperature of the melt in the crystallizer was 680 to 690° C., and the speed of ingot-drawing was 40 mm/min. High pressure water-cooling was applied at 400 mm close to the crystallizer, and air-cooling was applied at a lower region.

(15) (4) The Mg—Nd—Zn—Ca—Zr magnesium alloy semi-continuous ingot obtained from the casting had a size of Φ120×2400 mm. The ingot had an appearance free of cracks and shrinkage, with a smooth and clean surface, fine and uniform structures, and no solute segregation.

(16) (5) The resultant Mg—Nd—Zn—Ca—Zr magnesium alloy ingot was cut to a certain length, subjected to solid solution treatment at 520° C. for 10 hours, and then extruded at 330° C. to form a round rod having a diameter of Φ25 mm, and thus the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use was obtained.

(17) The degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use had a tensile strength of 277 MPa, a yield strength of 224 MPa and an elongation of 28%, as well as good plasticity and mechanical properties. The corrosion rate of the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use in artificial plasma was 0.24 mm/year, in a uniform corrosion manner. Biological test results showed that the material had no obvious cytotoxicity and good blood compatibility, which met the requirements for intravascular stent materials.

Example 3

(18) This example provides a degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use. The composition of the magnesium alloy comprises, with regard to a total weight of the magnesium alloy of 100%, 2.5% of Nd, 0.8% of Zn, 0.6% of Ca, 0.8% of Zr, and balance of Mg.

(19) The magnesium alloy was prepared by the following steps:

(20) (1) In a vacuum melting furnace, pure magnesium having a purity of 99.99 wt % or more, pure Zn having a purity of 99.99 wt % or more, pure Ca having a purity of 99.99 wt % or more, a Mg-30 wt % Nd master alloy and a Mg-30 wt % Zr master alloy were successively melted, and the melt temperature during melting was controlled at 740 to 760° C. After the raw materials were completely melted, argon gas was introduced to conduct gas stirring in a vacuum environment with a stirring time of 40 min.

(21) (2) After the stirring was completed, a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) was introduced to the surface of the melt for protection, and at the same time, the temperature of the melt was raised to 760 to 780° C. and kept for 30 to 40 min. After the high temperature insulation, the melting furnace was powered off, and the temperature of the melt was controlled at 700 to 720° C. and the melt was allowed to stand for 90 min.

(22) (3) Subsequently, a copper crystallizer was used for the ingot casting on a semi-continuous casting machine. The magnesium alloy melt was introduced into a diverter plate placed in the core of the inner sleeve of the crystallizer, and was diverted by the diverter plate into the space formed by the metal inner sleeve and the dummy bar of the crystallizer. At the same time, the protective gas ring was opened to provide a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) to the alloy melt for protection. During the semi-continuous casting process, the temperature of the melt in the vacuum melting furnace was controlled to 700 to 720° C., the temperature of the melt in the crystallizer was 680 to 690° C., and the speed of ingot-drawing was 40 mm/min. High pressure water-cooling was applied at 400 mm close to the crystallizer, and air-cooling was applied at a lower region.

(23) (4) The Mg—Nd—Zn—Ca—Zr magnesium alloy semi-continuous ingot obtained from the casting had a size of Φ120×2400 mm. The ingot had an appearance free of cracks and shrinkage, with a smooth and clean surface, fine and uniform structures, and no solute segregation.

(24) (5) The resultant Mg—Nd—Zn—Ca—Zr magnesium alloy ingot was cut to a certain length, subjected to solid solution treatment at 520° C. for 10 hours, and then extruded at 330° C. to form a round rod having a diameter of Φ25 mm, and thus the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use was obtained.

(25) The degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use had a tensile strength of 289 MPa, a yield strength of 232 MPa and an elongation of 25%, as well as good plasticity and mechanical properties. The corrosion rate of the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use in artificial plasma was 0.22 mm/year, in a uniform corrosion manner. Biological test results showed that the material had no obvious cytotoxicity and good blood compatibility, which met the requirements for intravascular stent materials.

Example 4

(26) This example provides a degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use. The composition of the magnesium alloy comprises, with regard to a total weight of the magnesium alloy of 100%, 1.5% of Nd, 0.4% of Zn, 0.4% of Zr, and balance of Mg.

(27) The magnesium alloy was prepared by the following steps:

(28) (1) In a vacuum melting furnace, pure magnesium having a purity of 99.99 wt % or more, pure Zn having a purity of 99.99 wt % or more, a Mg-30 wt % Nd master alloy and a Mg-30 wt % Zr master alloy were successively melted, and the melt temperature during melting was controlled at 740 to 760° C. After the raw materials were completely melted, argon gas was introduced to conduct gas stirring in a vacuum environment with a stirring time of 40 min.

(29) (2) After the stirring was completed, a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) was introduced to the surface of the melt for protection, and at the same time, the temperature of the melt was raised to 760 to 780° C. and kept for 30 min. After the high temperature insulation, the melting furnace was powered off, and the temperature of the melt was controlled at 700 to 720° C. and the melt was allowed to stand for 90 min.

(30) (3) Subsequently, a copper crystallizer was used for the ingot casting on a semi-continuous casting machine. The magnesium alloy melt was introduced into a diverter plate placed in the core of the inner sleeve of the crystallizer, and was diverted by the diverter plate into the space formed by the metal inner sleeve and the dummy bar of the crystallizer. At the same time, the protective gas ring was opened to provide a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) to the alloy melt for protection. During the semi-continuous casting process, the temperature of the melt in the vacuum melting furnace was controlled at 700 to 720° C., the temperature of the melt in the crystallizer was 680 to 690° C., and the speed of ingot-drawing was 40 mm/min. High pressure water-cooling was applied at 400 mm close to the crystallizer, and air-cooling was applied at a lower region.

(31) (4) The Mg—Nd—Zn—Zr magnesium alloy semi-continuous ingot obtained from the casting had a size of Φ120×2400 mm. The ingot had an appearance free of cracks and shrinkage, with a smooth and clean surface, fine and uniform structures, and no solute segregation.

(32) (5) The resultant Mg—Nd—Zn—Zr magnesium alloy ingot was cut to a certain length, subjected to solid solution treatment at 520° C. for 10 hours, and then extruded at 330° C. to form a round rod having a diameter of Φ25 mm, and thus the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use was obtained.

(33) The degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use had a tensile strength of 223 MPa, a yield strength of 188 MPa and an elongation of 24%. The corrosion rate of the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use in artificial plasma was 0.32 mm/year. Biological test results showed that the material had no obvious cytotoxicity and good blood compatibility, which met the requirements for the biocompatibility of intravascular stent materials.

Example 5

(34) This example provides a degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use. The composition of the magnesium alloy comprises, with regard to a total weight of the magnesium alloy of 100%, 1.5% of Nd, 0.4% of Zn, 0.4% of Ca, and balance of Mg.

(35) The magnesium alloy was prepared by the following steps:

(36) (1) In a vacuum melting furnace, pure magnesium having a purity of 99.99 wt % or more, pure Zn having a purity of 99.99 wt % or more, pure Ca having a purity of 99.99 wt % or more, and a Mg-30 wt % Zr master alloy were successively melted, and the melt temperature during melting was controlled at 740 to 760° C. After the raw materials were completely melted, argon gas was introduced to conduct gas stirring in a vacuum environment with a stirring time of 40 min.

(37) (2) After the stirring was completed, a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) was introduced to the surface of the melt for protection, and at the same time, the temperature of the melt was raised to 760 to 780° C. and kept for 30 min. After the high temperature insulation, the melting furnace was powered off, and the temperature of the melt was controlled at 700 to 720° C. and the melt was allowed to stand for 90 min.

(38) (3) Subsequently, a copper crystallizer was used for the ingot casting on a semi-continuous casting machine. The magnesium alloy melt was introduced into a diverter plate placed in the core of the inner sleeve of the crystallizer, and was diverted by the diverter plate into the space formed by the metal inner sleeve and the dummy bar of the crystallizer. At the same time, the protective gas ring was opened to provide a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) to the alloy melt for protection. During the semi-continuous casting process, the temperature of the melt in the vacuum melting furnace was controlled at 700 to 720° C., the temperature of the melt in the crystallizer was 680 to 690° C., and the speed of ingot-drawing was 40 mm/min. High pressure water-cooling was applied at 400 mm close to the crystallizer, and air-cooling was applied at a lower region.

(39) (4) The Mg—Nd—Zn—Ca magnesium alloy semi-continuous ingot obtained from the casting had a size of Φ120×2400 mm. The ingot had an appearance free of cracks and shrinkage, with a smooth and clean surface, fine and uniform structures, and no solute segregation.

(40) (5) The resultant Mg—Nd—Zn—Ca magnesium alloy ingot was cut to a certain length, subjected to solid solution treatment at 520° C. for 10 hours, and then extruded at 330° C. to form a round rod having a diameter of Φ25 mm, and thus the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use was obtained.

(41) The degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use had a tensile strength of 228 MPa, a yield strength of 196 MPa and an elongation of 21%. The corrosion rate of the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use in artificial plasma was 0.36 mm/year. Biological test results showed that the material had no obvious cytotoxicity and good blood compatibility, which met the requirements for the biocompatibility of intravascular stent materials.

Example 6

(42) This example provides a degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use. The composition of the magnesium alloy comprises, with regard to a total weight of the magnesium alloy of 100%, 1.5% of Nd, 2.0% of Zn, 0.4% of Ca, 0.4% of Zr, and balance of Mg.

(43) The magnesium alloy was prepared by the following steps:

(44) (1) In a vacuum melting furnace, pure magnesium having a purity of 99.99 wt % or more, pure Zn having a purity of 99.99 wt % or more, pure Ca having a purity of 99.99 wt % or more, a Mg-30 wt % Nd master alloy and a Mg-30 wt % Zr master alloy were successively melted, and the melt temperature during melting was controlled at 740 to 760° C. After the raw materials were completely melted, argon gas was introduced to conduct gas stirring in a vacuum environment with a stirring time of 40 min.

(45) (2) After the stirring was completed, a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) was introduced to the surface of the melt for protection, and at the same time, the temperature of the melt was raised to 760 to 780° C. and kept for 30 min. After the high temperature insulation, the melting furnace was powered off, and the temperature of the melt was controlled at 700 to 720° C. and the melt was allowed to stand for 90 min.

(46) (3) Subsequently, a copper crystallizer was used for the ingot casting on a semi-continuous casting machine. The magnesium alloy melt was introduced into a diverter plate placed in the core of the inner sleeve of the crystallizer, and was diverted by the diverter plate into the space formed by the metal inner sleeve and the dummy bar of the crystallizer. At the same time, the protective gas ring was opened to provide a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) to the alloy melt for protection. During the semi-continuous casting process, the temperature of the melt in the vacuum melting furnace was controlled at 700 to 720° C., the temperature of the melt in the crystallizer was 680 to 690° C., and the speed of ingot-drawing was 40 mm/min. High pressure water-cooling was applied at 400 mm close to the crystallizer, and air-cooling was applied at a lower region.

(47) (4) The Mg—Nd—Zn—Ca—Zr magnesium alloy semi-continuous ingot obtained from the casting had a size of Φ120×2400 mm. The ingot had an appearance free of cracks and shrinkage, with a smooth and clean surface, fine and uniform structures, and no solute segregation.

(48) (5) The resultant Mg—Nd—Zn—Ca—Zr magnesium alloy ingot was cut to a certain length, subjected to solid solution treatment at 520° C. for 10 hours, and then extruded at 330° C. to form a round rod having a diameter of Φ25 mm, and thus the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use was obtained.

(49) The degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use had a tensile strength of 256 MPa, a yield strength of 219 MPa and an elongation of 18%. The corrosion rate of the degradable corrosion-resistant high strength and ductility magnesium alloy for biomedical use in artificial plasma was 0.44 mm/year. Biological test results showed that the material had no obvious cytotoxicity and good blood compatibility, which met the requirements for the biocompatibility of intravascular stent materials.

Comparative Example 1

(50) This comparative example provides a biomedical magnesium alloy. The composition of the magnesium alloy comprises, with regard to a total weight of the magnesium alloy of 100%, 1.5% of Y, 0.4% of Zn, 0.4% of Zr, and balance of Mg.

(51) The magnesium alloy was prepared by the following steps:

(52) (1) In a vacuum melting furnace, pure magnesium having a purity of 99.99 wt % or more, pure Zn having a purity of 99.99 wt % or more, a Mg-30 wt % Y master alloy and a Mg-30 wt % Zr master alloy were successively melted, and the melt temperature during melting was controlled at 740 to 760° C. After the raw materials were completely melted, argon gas was introduced to conduct gas stirring in a vacuum environment with a stirring time of 40 min.

(53) (2) After the stirring was completed, a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) was introduced to the surface of the melt for protection, and at the same time, the temperature of the melt was raised to 760 to 780° C. and kept for 30 min. After the high temperature insulation, the melting furnace was powered off, and the temperature of the melt was controlled at 700 to 720° C. and the melt was allowed to stand for 90 min.

(54) (3) Subsequently, a copper crystallizer was used for the ingot casting on a semi-continuous casting machine. The magnesium alloy melt was introduced into a diverter plate placed in the core of the inner sleeve of the crystallizer, and was diverted by the diverter plate into the space formed by the metal inner sleeve and the dummy bar of the crystallizer. At the same time, the protective gas ring was opened to provide a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) to the alloy melt for protection. During the semi-continuous casting process, the temperature of the melt in the vacuum melting furnace was controlled at 700 to 720° C., the temperature of the melt in the crystallizer was 680 to 690° C., and the speed of ingot-drawing was 40 mm/min. High pressure water-cooling was applied at 400 mm close to the crystallizer, and air-cooling was applied at a lower region.

(55) (4) The Mg—Y—Zn—Zr magnesium alloy semi-continuous ingot obtained from the casting had a size of Φ120×2400 mm. The ingot had an appearance free of cracks and shrinkage, with a smooth and clean surface, fine and uniform structures, and no solute segregation.

(56) (5) The resultant Mg—Y—Zn—Zr magnesium alloy ingot was cut to a certain length, subjected to solid solution treatment at 520° C. for 10 hours, and then extruded at 330° C. to form a round rod having a diameter of Φ25 mm, and thus the biomedical corrosion resistant high strength and toughness magnesium alloy was obtained.

(57) The biomedical magnesium alloy had a tensile strength of 216 MPa, a yield strength of 176 MPa and an elongation of 19%. The corrosion rate of the biomedical magnesium alloy in artificial plasma was 0.37 mm/year.

Comparative Example 2

(58) This comparative example provides a biomedical magnesium alloy. The composition of the magnesium alloy comprises, with regard to a total weight of the magnesium alloy of 100%, 1.5% of Y, 0.4% of Zn, 0.4% of Ca, and balance of Mg.

(59) The magnesium alloy was prepared by the following steps:

(60) (1) In a vacuum melting furnace, pure magnesium having a purity of 99.99 wt % or more, pure Zn having a purity of 99.99 wt % or more, pure Ca having a purity of 99.99 wt % or more, and a Mg-30 wt % Y master alloy were successively melted, and the melt temperature during melting was controlled at 740 to 760° C. After the raw materials were completely melted, argon gas was introduced to conduct gas stirring in a vacuum environment with a stirring time of 40 min.

(61) (2) After the stirring was completed, a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) was introduced to the surface of the melt for protection, and at the same time, the temperature of the melt was raised to 760 to 780° C. and kept for 30 min. After the high temperature insulation, the melting furnace was powered off, and the temperature of the melt was controlled at 700 to 720° C. and the melt was allowed to stand for 90 min.

(62) (3) Subsequently, a copper crystallizer was used for the ingot casting on a semi-continuous casting machine. The magnesium alloy melt was introduced into a diverter plate placed in the core of the inner sleeve of the crystallizer, and was diverted by the diverter plate into the space formed by the metal inner sleeve and the dummy bar of the crystallizer. At the same time, the protective gas ring was opened to provide a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) to the alloy melt for protection. During the semi-continuous casting process, the temperature of the melt in the vacuum melting furnace was controlled at 700 to 720° C., the temperature of the melt in the crystallizer was 680 to 690° C., and the speed of ingot-drawing was 40 mm/min. High pressure water-cooling was applied at 400 mm close to the crystallizer, and air-cooling was applied at a lower region.

(63) (4) The Mg—Y—Zn—Ca magnesium alloy semi-continuous ingot obtained from the casting had a size of Φ120×2400 mm. The ingot had an appearance free of cracks and shrinkage, with a smooth and clean surface, fine and uniform structures, and no solute segregation.

(64) (5) The resultant Mg—Y—Zn—Ca magnesium alloy ingot was cut to a certain length, subjected to solid solution treatment at 520° C. for 10 hours, and then extruded at 330° C. to form a round rod having a diameter of Φ25 mm, and thus the biomedical magnesium alloy was obtained.

(65) The biomedical magnesium alloy had a tensile strength of 213 MPa, a yield strength of 172 MPa and an elongation of 22%. The corrosion rate of the biomedical magnesium alloy in artificial plasma was 0.43 mm/year.

Comparative Example 3

(66) This comparative example provides a biomedical magnesium alloy. The composition of the magnesium alloy comprises, with regard to a total weight of the magnesium alloy of 100%, 1.5% of Y, 2.0% of Zn, 0.4% of Ca, and balance of Mg.

(67) The magnesium alloy was prepared by the following steps:

(68) (1) In a vacuum melting furnace, pure magnesium having a purity of 99.99 wt % or more, pure Zn having a purity of 99.99 wt % or more, pure Ca having a purity of 99.99 wt % or more, a Mg-30 wt % Y master alloy and a Mg-30 wt % Zr master alloy were successively melted, and the melt temperature during melting was controlled at 740 to 760° C. After the raw materials were completely melted, argon gas was introduced to conduct gas stirring in a vacuum environment with a stirring time of 40 min.

(69) (2) After the stirring was completed, a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) was introduced to the surface of the melt for protection, and at the same time, the temperature of the melt was raised to 760 to 780° C. and kept for 30 min. After the high temperature insulation, the melting furnace was powered off, and the temperature of the melt was controlled at 700 to 720° C. and the melt was allowed to stand for 90 min.

(70) (3) Subsequently, a copper crystallizer was used for the ingot casting on a semi-continuous casting machine. The magnesium alloy melt was introduced into a diverter plate placed in the core of the inner sleeve of the crystallizer, and was diverted by the diverter plate into the space formed by the metal inner sleeve and the dummy bar of the crystallizer. At the same time, the protective gas ring was opened to provide a mixed gas of SF.sub.6 and CO.sub.2 (volume ratio of SF.sub.6:CO.sub.2 in this mixed gas being 1:100) to the alloy melt for protection. During the semi-continuous casting process, the temperature of the melt in the vacuum melting furnace was controlled at 700 to 720° C., the temperature of the melt in the crystallizer was 680 to 690° C., and the speed of ingot-drawing was 40 mm/min. High pressure water-cooling was applied at 400 mm close to the crystallizer, and air-cooling was applied at a lower region.

(71) (4) The Mg—Y—Zn—Ca—Zr magnesium alloy semi-continuous ingot obtained from the casting had a size of Φ120×2400 mm. The ingot had an appearance free of cracks and shrinkage, with a smooth and clean surface, fine and uniform structures, and no solute segregation.

(72) (5) The resultant Mg—Y—Zn—Ca—Zr magnesium alloy ingot was cut to a certain length, subjected to solid solution treatment at 520° C. for 10 hours, and then extruded at 330° C. to form a round rod having a diameter of Φ25 mm, and thus the biomedical magnesium alloy was obtained.

(73) The biomedical magnesium alloy had a tensile strength of 236 MPa, a yield strength of 204 MPa and an elongation of 17%. The corrosion rate of the biomedical magnesium alloy in artificial plasma was 0.48 mm/year.

(74) TABLE-US-00001 TABLE 1 Magnesium alloy composition and related properties Tensile Yield Corrosion Composition strength Strength Elongation rate Corrosion Example No. (wt %) (MPa) (MPa) (%) (mm/year) mode Example 1 Mg—1.5Nd—0.4Zn—0.4Ca—0.4Zr 246 207 34 0.26 Uniform corrosion Example 2 Mg—2.0Nd—0.6Zn—0.5Ca—0.6Zr 277 224 28 0.24 Uniform corrosion Example 3 Mg—2.5Nd—0.8Zn—0.6Ca—0.8Zr 289 232 25 0.22 Uniform corrosion Example 4 Mg—1.5Nd—0.4Zn—0.4Zr 223 188 24 0.32 — Example 5 Mg—1.5Nd—0.4Zn—0.4Ca 228 196 21 0.36 — Example 6 Mg—1.5Nd—2.0Zn—0.4Ca—0.4Zr 256 219 18 0.44 — Comparative Mg—1.5Y—0.4Zn—0.4Zr 216 176 19 0.37 — Example 1 Comparative Mg—1.5Y—0.4Zn—0.4Ca 213 172 22 0.43 — Example 2 Comparative Mg—1.5Y—2.0Zn—0.4Ca—0.4Zr 236 204 17 0.48 — Example 3

(75) As can be seen from Table 1, the magnesium alloy prepared by implementing the most preferred embodiments of the present disclosure has a tensile strength of 246 to 289 MPa, a yield strength of 207 to 232 MPa and an elongation rate of up to 25 to 34%, which meets the requirements for the mechanical properties of intravascular stent materials. Its corrosion rate in artificial plasma can reach 0.22 to 0.26 mm/year, which meets the requirement for the corrosion resistance of intravascular stent materials. In addition, the magnesium alloy has no obvious cytotoxicity and good blood compatibility, which meets the requirements for the biocompatibility of intravascular stent materials.