BIODEGRADABLE MAGNESIUM ALLOY WITHOUT RARE EARTH ELEMENTS, PREPARATION METHOD AND USE THEREOF

Abstract

The present application provides a biodegradable magnesium alloy without rare earth elements. The magnesium alloy comprises the following elements in percentage by mass: Zn 1.0-5.0%; Mn 0.1-1.0%; Ca 0.1-1.0%; Sr 0.1-1.0%; Sn 0.1-3.0%; Zr 0.1-0.8%; and Mg balance. The impurity in the magnesium alloy does not contain rare earth elements. The present application also provides a method for preparing the above biodegradable magnesium alloy and use in the preparation of medical devices. In the present application, Mg is used as the main components and mixed with a specific proportion of Zn, Ca and Mn to prepare the alloy. The biodegradable magnesium alloy of the present application has a controllable degradation rate and strong mechanical strength, and there are no harmful elements to a human body, and the degradation of the alloy in the human body will not affect human body.

Claims

1. A biodegradable magnesium alloy without rare earth elements, comprising the following elements in percentage by mass: TABLE-US-00004 Zn 1.0-5.0%; Mn 0.1-1.0%; Ca 0.1-1.0%; Sr 0.1-1.0%; Sn 0.1-3.0%; Zr 0.1-0.8%; and Mg balance[[;]], wherein, the biodegradable magnesium alloy has an average grain size of 5-10 m, and an average density of microcrack distribution on a surface of the biodegradable magnesium alloy is less than or equal to 20 microcracks/mm.sup.2.

2. The biodegradable magnesium alloy without rare earth elements of claim 1, wherein the biodegradable magnesium alloy comprises 1.0-3.0% of Zn, 0.5-1.0% of Ca, 0.5-1.0% of Mn and 0.3-0.5% of Zr.

3. The biodegradable magnesium alloy without rare earth elements of claim 1, wherein a mass ratio of an impurity in the biodegradable magnesium alloy is 0.003 wt % or less.

4. The biodegradable magnesium alloy without rare earth elements of claim 1, wherein an impurity in the biodegradable magnesium alloy does not contain aluminum.

5. A method for preparing a biodegradable magnesium alloy of claim 1 comprising the steps of: melting-casting, wherein in a closed container, fully adding each of the elements into a melting ladle according to the required proportion, controlling a temperature to melt the elements at 700-800 C., blowing an argon gas on and stirring of the elements to obtain the magnesium alloy, and casting and cooling to obtain the biodegradable magnesium alloy; heat treating the biodegradable magnesium alloy by heating the biodegradable magnesium alloy obtained by the melting-casting between about 200-250 C., annealing for 1-5 min, and cooling to obtain a heat-treated biodegradable magnesium alloy; hot extruding the heat-treated biodegradable alloy by putting the heat-treated biodegradable alloy into a hot extrusion mold, controlling the temperature of the heat-treated biodegradable alloy to be between about 250-300 C., controlling an extrusion rate to be between about 2-5 mm/s, and setting an extrusion ratio to be between about 10-15:1 to obtain a hot-extruded biodegradable magnesium alloy; and rolling and forming the hot-extruded biodegradable magnesium alloy by rolling the hot-extruded biodegradable magnesium alloy at a temperature between about of 320-350 C., controlling a speed to be between about 20-30 m/min, and controlling the reduction of each rolling to be between about 50-80%, to obtain a formed biodegradable magnesium alloy.

6. The method for preparing a biodegradable magnesium alloy without rare earth elements of claim 5, wherein, after the rolling and forming is completed, a further heat treatment process is carried out.

7. The method for preparing a biodegradable magnesium alloy without rare earth elements of claim 5, wherein preheating is carried out before the rolling and forming, and a preheating time does not exceed 10 minutes.

8. The method for preparing a biodegradable magnesium alloy without rare earth elements of claim 5, wherein a number of passes for the rolling and forming is no more than 10.

9. The method for preparing a biodegradable magnesium alloy without rare earth elements of claim 5, wherein during the melting-casting, the argon gas is blowing through a gas port at a bottom of the melting ladle.

10. A method for making medical devices comprising using the biodegradable magnesium alloy without rare earth elements of claim 1 to make an orthopedic implant, an intracardiac intervention stent, or a vascular intervention stent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is the microstructure comparison diagrams of the cross sections of the samples of example 1 and comparative example 1 according to the present application;

[0030] FIG. 2 is the microstructure morphology comparison diagrams of the surface of the samples of example 1 and comparative example 1 according to the present application; and

[0031] FIG. 3 is the tensile-strain curve comparison diagram of the samples of examples 1-3 and comparative example 1.

DETAILED DESCRIPTION

[0032] The embodiments of the present application are described in detail below, the examples of which are shown in the drawings, wherein the same or similar reference numbers represent the same or similar modules or modules having the same or similar functions throughout. The embodiments described below with reference to the attached drawings are illustrative and are only used to explain the present application and should not be construed as limiting the present invention.

[0033] In the description of the present invention, description with reference to terms one embodiment, another embodiment, etc., means that a specific feature, structure, material or characteristic described in combination with that embodiment that are included in at least one embodiment of present application. In the description, the schematic representation of the above terms does not have to refer to the same embodiment or example. Moreover, the described specific features, structures, materials, or features may be combined in a suitable manner in any one or more embodiments or examples. In addition, the technical features involved in different embodiments or examples of the present invention described in the description can be combined with each other as long as they do not constitute a conflict between them.

[0034] The magnesium alloy used in the orthopedic implants of the present application is based on Mg as main phase, mixed with other alloy elements, and does not contain rare earth elements. Generally, magnesium alloys for such orthopedic implants require a certain strength and degradation rate. In terms of strength, the tensile strength and yield strength of the magnesium alloy obtained by the present application are both over 250 MPa; in terms of degradation rate, the degradable magnesium alloy in the present application has a degradation rate of 0.5-1.5 mm/year in simulated body fluid. Compared with the conventional magnesium alloy in the prior art, the magnesium alloys for orthopedic implants in the following embodiments of the present application have significant corrosion resistance, and especially have obvious inhibitory effect on the formation of pitting corrosion. The regulation of the corrosion rate is the main contribution of the proposed magnesium alloy of the present application to the prior art, because when the magnesium alloy is implanted into the organism, it is necessary to ensure that the implant has sufficient strength without being lost by large area corrosion for a period of time, and optionally does not affect the healing process of the organism itself. In addition, the magnesium alloy in the present application shows excellent strength.

[0035] In terms of morphology, the embodiments of the present application can obtain degradable magnesium alloy, and control that there are no large area, irregular columnar or strip grains or obvious grain structure with obvious length-diameter ratio. Optionally, equiaxial fine grains with uniform grain size distribution and relatively dense surface layer structure distribution are obtained. These morphological characteristics, in particular, make it particularly advantageous to use the magnesium alloys of the present application as alloy materials, for example, for biodegradable orthopedic implants.

[0036] The biodegradable magnesium alloy obtained in the present application can be widely used as an orthopedic implant, an intracardiac intervention stent or a vascular intervention stent, and widely used (or used after molding and processing) as nails, screws, suturing nails, fixation plates, bending rods, joint bolts, locking bolts, intraspinal stents, honeycomb supports, etc. in vivo, which satisfy the needs of organisms.

[0037] Some specific experimental steps or conditions not indicated in the examples can be carried out according to the operation or conditions of conventional experimental steps described in the literature in this field.

[0038] The powder purity of metal raw materials used in the following examples and comparative example is not less than 99.999%. The manufacturer of the reagents or instruments used are not indicated, which are all commercially available conventional reagent products.

Example 1

[0039] The present example provides a biodegradable magnesium alloy without rare earth elements, the preparation method comprises the following steps of: 91 parts of Mg, 4 parts of Zn, 1 part of Ca, 1 part of Mn, 0.8 parts of Zr, 2 parts of Sn and 0.2 parts of Sr metal powder are mixed well before casting, and then cast at 700 C.; heat treatment: the casting alloy is heated, the temperature is controlled at 200 C., annealed for 1 min, and cooled; hot extrusion: the heat-treated alloy is put into the hot extrusion mold, the temperature is controlled at 300 C., the extrusion rate is controlled at 5 mm/s, and the extrusion ratio is set to 10:1; Rolling and forming: rolling is carried out at 350 C., the speed is controlled at 30 m/min, the reduction of each rolling is controlled at 60%, and passes for the rolling are no more than 10 times to obtain a formed biodegradable magnesium alloy.

Example 2

[0040] The present example provides a biodegradable magnesium alloy without rare earth elements, the preparation method comprises the following steps of: 89.2 parts of Mg, 5 parts of Zn, 1 part of Ca, 1 part of Mn, 0.8 parts of Zr, 2 parts of Sn and 1 parts of Sr metal powder are mixed well before casting, and then cast at 750 C.; heat treatment: the casting alloy is heated, the temperature is controlled at 250 C., annealed for 2 min, and cooled; hot extrusion: the heat-treated alloy is put into the hot extrusion mold, the temperature is controlled at 300 C., the extrusion rate of is controlled at 5 mm/s, and the extrusion ratio is set to 15:1; Rolling and forming: rolling is carried out at 350 C., the speed is controlled at 20 m/min, the reduction of each rolling is controlled at 50%, and passes for the rolling are no more than 10 times to obtain a formed biodegradable magnesium alloy.

Example 3

[0041] The present example provides a biodegradable magnesium alloy without rare earth elements, the preparation method comprises the following steps of: 90 parts of Mg, 5 parts of Zn, 1 part of Ca, 1 part of Mn, 0.8 parts of Zr, 1.2 parts of Sn and 1 parts of Sr metal powder are mixed well before casting, and then cast at 700 C.; heat treatment: the casting alloy is heated, the temperature is controlled at 200 C., annealed for 1 min, and cooled; hot extrusion: the heat-treated alloy is put into the hot extrusion mold, the temperature is controlled at 250 C., the extrusion rate of is controlled at 5 mm/s, and the extrusion ratio is set to 15:1; Rolling and forming: rolling is carried out at 320 C., the speed is controlled at 30 m/min, the reduction of each rolling is controlled at 80%, and passes for the rolling are no more than 10 times to obtain a formed biodegradable magnesium alloy.

Comparative Example 1

[0042] Except for the heat treatment in step 2), other parameters and processes in this comparative example are the same as those in example 1.

Alloy Microstructure Morphology Test

[0043] The magnesium alloys obtained from example 1 and the comparative example 1 were taken for sample preparation, and the microstructure was observed and compared. The microstructure comparison of the cross section of the sample of example 1 and the comparative example 1 of the present application is shown in FIG. 1. It can be clearly seen that compared with the sample of the comparative example 1, the grain size of the magnesium alloy sample obtained by the present application method is more uniform, indicating that the recrystalization of the structure in the process is more complete; at the same time, the grains are finer and the segregation phase is less, indicating that the preheating treatment reduces the precipitate and reduces the resistance of the grain to re-refined crystallization.

[0044] The microstructure morphology comparison of the surface of the sample of example 1 and the comparative example 1 of the present application is shown in FIG. 2. It can be seen from the comparison that the cracks on the surface of the magnesium alloy sample obtained by the method of the present application are obviously suppressed, and the width, length and density of the cracks are significantly reduced. The crack density of the surface film in the present application is lower than 20 microcracks/mm.sup.2, while the crack density of the surface film of the sample of the comparative example 1 is higher than 100 microcracks/mm.sup.2.

Alloy Strength Property Test

[0045] The tensile strength, yield strength and elongation of the biodegradable magnesium alloy obtained from examples 1-3 and the comparative example 1 are measured according to GB-T228-2002, and the strength index is tested. The test results are shown in Table 1 and FIG. 3:

TABLE-US-00002 TABLE 1 Tensile Yield Sample strength MPa strength MPa Elongation Example 1 330 300 21 Example 2 330 280 21 Example 3 300 255 21 Comparative example 1 255 225 17

[0046] It can be intuitively shown from the tensile-strain curves in FIG. 3 that the yield strength of the magnesium alloy obtained from Examples 1-3 is greater than 250 MPa, the tensile strength is greater than 275 MPa, and the elongation is greater than 20%. The yield strength and tensile strength of the magnesium alloy sample of the comparative example 1 are lower than 225 MPa and 260 MPa, and the elongation is lower than 17%. Therefore, compared with the sample of the comparative example, the strength performance of the sample in the present application has been improved by at least 10-20% or more.

Alloy Degradability

[0047] The biodegradable magnesium alloy obtained in Examples 1-3 and the comparative example 1 is made into bars. Each bar has a thickness of 1 mm and a diameter of 10 mm and is immersed in 37% physiological saline to simulate the degradation by body fluids in the human body. The simulation test results are shown in the table below:

TABLE-US-00003 TABLE 2 Comparative Sample Example 1 Example 2 Example 3 example 1 Degradation 0.89 1.17 1.35 1.91 rate mm/Y

[0048] It can be seen from the above table that the biodegradable magnesium alloys obtained by the examples of the present application have a good control of degradation rate in the simulated body fluid, and can provide strength for a certain time while meeting the healing time of the organism's own tissue. However, the rapid and uncontrollable degradation rate of the comparative example 1 is unfavorable for the control of precipitates after degradation and the maintenance of implant strength.

[0049] Obviously, the above-mentioned embodiments are merely examples made for clear description, but do not limit the implementation. For those of ordinary skill in the art, other different forms of variations or modifications can also be made on the basis of the above-mentioned description. All embodiments are not necessary to be and cannot be exhaustively listed herein. In addition, the obvious variations or modifications derived therefrom all fall within the scope of protection of the present invention.