CN115287476A - Preparation method and application of medical magnesium alloy capable of being uniformly degraded - Google Patents

Abstract

The invention discloses a preparation method of a medical magnesium alloy capable of being uniformly degraded, which comprises the following steps: s1) weighing each material according to the mass percentage of the designed components; s2) smelting the materials weighed in the S1) under a protective atmosphere, refining, and finally casting into a cast ingot; s3) homogenizing the ingot casting obtained in the S2); s4) carrying out extrusion deformation treatment on the cast ingot treated in the S3) to obtain a magnesium alloy; and S5) annealing the extruded magnesium alloy obtained in the step S4), and air-cooling to obtain the medical magnesium alloy with uniform corrosion characteristics and uniform degradation. The alloy of the invention is subjected to component design, heat treatment and extrusion to obtain the alloy with uniform corrosivity and mechanical properties. The medical magnesium alloy can meet the requirements of medical application fields such as cardiovascular stents, medical bone nails and anastomosis nails on material corrosion performance and mechanical property, has uniformly distributed grain structures, and shows excellent strong plasticity and corrosion resistance.

Description

A preparation method and application of uniformly degradable medical magnesium alloy

technical field

The invention belongs to the field of degradable medical materials, and in particular relates to a preparation method of a uniformly degradable medical magnesium alloy.

Background technique

At present, magnesium alloy has good biocompatibility, its density is close to that of human compact bone (1.75g/cm3), and its elastic modulus is also close to that of human bone (10-40GPa), which can avoid the stress shielding effect. In addition, magnesium alloy also has good biodegradability, compared with stainless steel and titanium alloy, it can avoid the pain caused by secondary surgery. Although medical polymer materials can also be degraded, they have poor mechanical properties and are difficult to be used as support materials. As a biomedical material, magnesium alloy has excellent mechanical properties and the characteristics of degradable absorption, and has great potential as a biodegradable medical material. However, the chemical properties of magnesium alloys are active, and localized corrosion is easy to occur if they corrode too quickly in the human environment, resulting in premature loss of mechanical properties, thus losing the fixation and support of the implanted position.

Therefore, it is necessary to develop new medical magnesium alloys with uniform degradation.

Contents of the invention

In order to overcome the above-mentioned shortcomings of excessively fast degradation and uneven corrosion of magnesium alloys for medical use, the purpose of the present invention is to provide a preparation method that can uniformly degrade medical magnesium alloys. The alloy has good corrosion resistance and mechanical properties.

The present invention is achieved through the following technical solutions: a method for preparing a uniformly degradable medical magnesium alloy, the method specifically comprising the following steps:

S1) Weigh each material according to the mass percentage of the designed components, the material contains Gd, and the mass percentage of Gd is less than 1%;

S2) Smelting each material weighed in S1) under a protective atmosphere, then refining, and finally casting into ingots;

S3) Homogenize the ingot obtained from S2);

S4) Extruding and deforming the cast ingot after S3) to obtain a magnesium alloy;

S5) performing annealing treatment on the extruded magnesium alloy obtained in S4), and after air cooling, a uniformly degradable medical magnesium alloy with uniform corrosion characteristics is obtained.

The above S4) and S5) are necessary steps in the process of the present invention, and the order of the two cannot be changed, otherwise the uniformly degradable medical magnesium alloy of the present invention cannot be obtained. After the components of the present application are combined with it, the alloy matrix has Uniformly distributed α-Mg grain structure and Mg3Zn3Gd2 precipitated phase are indispensable.

Further, the matrix of the uniformly degradable medical magnesium alloy has uniformly distributed α-Mg grain structure and Mg3Zn3Gd2 precipitated phase, and the size of the α-Mg grain structure is 8-15 μm; and the Mg3Zn3Gd2 precipitated phase and the magnesium alloy The potential difference between the substrates is 0.13-0.14v.

Further, the tensile strength of the uniformly degradable medical magnesium alloy at room temperature is 229-247 MPa, the yield strength is 138-158 MPa, and the elongation at room temperature is 19-28%. After soaking in simulated body fluid for 480 hours, the weight loss rate is 0.218-0.354mm/year.

Further, the mass percentage of each element in each material in S1) is: Zn 1.5-2.0%, Mn: 0.3-0.6%, Gd: 0.45-0.79%, Sr: 0.15-0.3%, and the rest is Mg and unavoidable impurity elements.

Further, the sum of the mass percentages of the inevitable impurity elements is less than 0.015%, and Fe<0.005%, Ni<0.005%, and Cu<0.005% among the inevitable impurities.

Further, the specific process in said S2) is:

First keep warm at a temperature of 750-780°C for 30-60 minutes, stir for 5-10 minutes after the materials are melted, then cool down to 720-740°C and refine for 5-10 minutes, after refining, raise the temperature to 750-780°C and let stand for 6-8 minutes. The melt temperature is lowered to 700-720°C for casting.

Further, the homogenization treatment in S3) adopts two-stage homogenization heat treatment, and the process parameters are: the temperature is 350-480° C., and the holding time is 16-24 hours.

Further, the extrusion deformation temperature in S4) is 400° C., and the extrusion ratio is 16:1.

Further, the temperature of the annealing treatment in S5) is 200-250° C., and the holding time is 0.5-1 h.

Further, the materials of S1) are high-purity magnesium ingots with a purity of 99.99%, high-purity zinc ingots with a purity of 99.99%, Mg-5%Mn, Mg-25%Gd and Mg-20%Sr master alloys.

A uniformly degradable medical magnesium alloy prepared by the above method is applied to the preparation of cardiovascular stents, medical bone nails and staples.

The beneficial effects of the present invention are as follows:

(1) A uniform degradable medical magnesium alloy prepared by the present invention has a uniform grain structure and uniformly distributed Mg3Zn3Gd2 precipitates, wherein the potential difference between Mg3Zn3Gd2 and the magnesium alloy matrix is 0.13 to 0.14v, and the driving force of galvanic corrosion Small. After the addition of rare earth Gd elements to magnesium alloys, the hydration of the corrosion film layer is reduced during the corrosion process, the stability of the corrosion product layer is increased, the compactness of the corrosion film layer is improved, and the substrate is protected to a certain extent.

(2) The present invention has uniform corrosion and mechanical properties through component design, heat treatment and extrusion molding. The obtained alloy can meet the requirements of material corrosion performance and mechanical performance in medical application fields such as cardiovascular stents, medical bone nails and staples.

(3) The preparation method of the uniformly degradable medical magnesium alloy described in the present invention is simple and low in cost, and can realize industrial production.

Description of drawings

Fig. 1 is a flowchart of a method for preparing a uniformly degradable medical magnesium alloy according to the present invention.

Fig. 2 is a schematic diagram of the metallographic microstructure of the alloy prepared in Example 1 using the method of the present invention.

Fig. 3 is a schematic diagram of the metallographic microstructure of the alloy prepared in Example 2 using the method of the present invention.

Fig. 4 is a schematic diagram of the metallographic microstructure of the alloy prepared in Example 3 using the method of the present invention.

Fig. 5 is a schematic diagram of the metallographic microstructure of the alloy prepared in Example 4 using the method of the present invention.

Fig. 6 is a schematic diagram of the TEM microstructure of the alloy prepared in Example 1 using the method of the present invention.

Fig. 7 is a schematic diagram of the TEM microstructure of the alloy prepared in Example 2 using the method of the present invention.

Fig. 8 is a schematic diagram of the TEM microstructure of the alloy prepared in Example 3 using the method of the present invention.

Fig. 9 is a schematic diagram of the TEM microstructure of the alloy prepared in Example 4 using the method of the present invention.

Fig. 10 is the 3D morphology of the alloy prepared in Example 1 using the method of the present invention after immersion in simulated body fluid for 480 hours after removal of corrosion products.

Fig. 11 is the 3D morphology of the alloy prepared in Example 2 using the method of the present invention after immersion in simulated body fluid for 480 hours after removal of corrosion products.

Fig. 12 is the 3D morphology of the alloy prepared in Example 3 using the method of the present invention after immersion in simulated body fluid for 480 hours after removal of corrosion products.

Fig. 13 is the 3D morphology of the alloy prepared in Example 4 using the method of the present invention after immersion in simulated body fluid for 480 hours after removal of corrosion products.

Detailed ways

The present invention is further described below by accompanying drawing and specific embodiment, but be limited to following embodiment, the equivalent technical scheme of other application field also belongs to category of the present invention, and the scope of patent protection of the present invention should be limited by each claim.

As shown in Figure 1, a method for preparing a uniformly degradable medical magnesium alloy of the present invention, the method specifically includes the following steps:

S1) Weigh each material according to the mass percentage of the designed components, the material contains Gd, and the mass percentage of Gd is less than 1%;

S2) Smelting each material weighed in S1) under a protective atmosphere, then refining, and finally casting into ingots;

S3) Homogenize the ingot obtained from S2);

S4) Extruding and deforming the cast ingot after S3) to obtain a magnesium alloy;

S5) performing annealing treatment on the extruded magnesium alloy obtained in S4), and after air cooling, a uniformly degradable medical magnesium alloy with uniform corrosion characteristics is obtained.

The uniformly degradable medical magnesium alloy matrix has uniformly distributed α-Mg grain structure and Mg3Zn3Gd2 precipitated phase, the size of the α-Mg grain structure is 8-15 μm; and the Mg3Zn3Gd2 precipitated phase and the magnesium alloy matrix The potential difference between them is 0.13~0.14v.

The tensile strength of the uniformly degradable medical magnesium alloy at room temperature is 229-247 MPa, the yield strength is 138-158 MPa, and the elongation at room temperature is 19-28%. After soaking in simulated body fluid for 480 hours, the weight loss rate is 0.218-0.354mm/year.

The mass percentages of each element in each material in S1) are: Zn 1.5-2.0%, Mn: 0.3-0.6%, Gd: 0.45-0.79%, Sr: 0.15-0.3%, and the rest are Mg and unavoidable impurity elements .

The sum of the mass percentages of the inevitable impurity elements is less than 0.015%, and Fe<0.005%, Ni<0.005%, and Cu<0.005% among the inevitable impurities.

The concrete process in said S2) is:

First keep warm at a temperature of 750-780°C for 30-60 minutes, stir for 5-10 minutes after the materials are melted, then cool down to 720-740°C and refine for 5-10 minutes, after refining, raise the temperature to 750-780°C and let stand for 6-8 minutes. The melt temperature is lowered to 700-720°C for casting.

The homogenization treatment in S3) adopts two-stage homogenization heat treatment, and the process parameters are as follows: the temperature is 350-480° C., and the holding time is 16-24 hours.

The extrusion deformation temperature in S4) is 400° C., and the extrusion ratio is 16:1.

The temperature of the annealing treatment in S5) is 200-250° C., and the holding time is 0.5-1 h.

The materials of S1) are high-purity magnesium ingots with a purity of 99.99%, high-purity zinc ingots with a purity of 99.99%, Mg-5%Mn, Mg-25%Gd and Mg-20%Sr master alloys.

A uniformly degradable medical magnesium alloy prepared by the above-mentioned method is applied to the fields of cardiovascular stents, medical bone nails and staples.

Example 1:

According to the mass percentage, it is prepared from the following components: Zn 1.7%, Mn 0.45%, Gd 0.45%, Sr 0.15%, and the rest are Mg and unavoidable impurity elements. The specific preparation method is as follows:

S1) Weigh the material by mass percentage, the material is high-purity magnesium ingot, high-purity zinc ingot, Mg-5%Mn master alloy, Mg-25%Gd master alloy and Mg-20%Sr master alloy;

S2) Ingot smelting: smelting under the protection of high-purity argon, heating pure magnesium to 720°C for melting, then adding Mg-5%Mn master alloy and Mg-25%Gd master alloy in turn, and raising the temperature of the melt Heat it up to 740-760°C for 10-20 minutes, cool down to 720°C, add pure zinc and Mg-20%Sr master alloy, fully stir at 720°C for 5-10 minutes, refine and degas and remove surface scum, and cast to graphite mold;

S3) casting the alloy melt obtained in S2) into an ingot at 720° C. by gravity casting;

S4) Homogenization heat treatment: put the above-mentioned cast ingot in S3) in a vacuum heat treatment furnace protected by high-purity argon, first raise the temperature to 350°C at a heating rate of 5°C/min and keep it warm for 4h, and then heat at the same heating rate To 420 ℃ holding time for 20h, and then processed into extrusion billets;

S5) Hot extrusion: preheat the extrusion billet at 400°C for 0.5-1h, apply molybdenum disulfide grease on the surface, and extrude through an extruder at a temperature of 400°C and an extrusion ratio of 16:1 ;

S6) Annealing treatment: the extruded material is kept at 200°C for 0.5h, and air-cooled.

The room temperature yield strength of the magnesium alloy obtained in the embodiment S6) is 138 MPa, the room temperature tensile strength is 229 MPa, and the room temperature elongation is 28%. After soaking in simulated body fluid for 480h, the weight loss rate was 0.218mm/year. The metallographic microstructure of the obtained magnesium alloy is shown in Figure 2; the TEM microstructure of the alloy is shown in Figure 6; the alloy was soaked in simulated body fluid The 3D morphology after removing the corrosion products after 480h is shown in Figure 10.

Example 2:

According to the mass percentage, it is prepared from the following components: Zn 1.85%, Mn 0.45%, Gd 0.6%, Sr 0.15%, and the rest are Mg and unavoidable impurity elements. The specific preparation method is as follows:

S1) Weigh the material by mass percentage, the material is high-purity magnesium ingot, high-purity zinc ingot, Mg-5%Mn master alloy, Mg-25%Gd master alloy and Mg-20%Sr master alloy;

S2) Ingot smelting: smelting under the protection of high-purity argon, heating pure magnesium to 720°C for melting, then adding Mg-5%Mn master alloy and Mg-25%Gd master alloy in turn, and raising the temperature of the melt Heat it up to 740-760°C for 10-20 minutes, cool down to 720°C, add pure zinc and Mg-20%Sr master alloy, fully stir at 720°C for 5-10 minutes, refine and degas and remove surface scum, and cast to graphite mold;

S3) casting the alloy melt obtained in S2) into an ingot at 720° C. by gravity casting;

S4) Homogenization heat treatment: put the above-mentioned cast ingot in S3) in a vacuum heat treatment furnace protected by high-purity argon, first raise the temperature to 350°C at a heating rate of 5°C/min and keep it warm for 4h, and then heat at the same heating rate To 460 ℃ holding time for 20h, and then processed into extrusion billets;

S5) Hot extrusion: preheat the extrusion billet at 400°C for 0.5-1h, apply molybdenum disulfide grease on the surface, and extrude through an extruder at a temperature of 400°C and an extrusion ratio of 16:1 ;

S6) Annealing treatment: the extruded material is kept at 200° C. for 1 hour, and air-cooled.

The room temperature yield strength of the magnesium alloy obtained in the embodiment S6) is 154 MPa, the room temperature tensile strength is 233 MPa, and the room temperature elongation is 24%. After soaking in simulated body fluid for 480 hours, the weight loss rate is 0.287mm/year.

The metallographic microstructure of the obtained magnesium alloy is shown in Figure 3; the TEM microstructure of the alloy is shown in Figure 7; the 3D morphology of the alloy after removing corrosion products after soaking in simulated body fluid for 480 hours is shown in Figure 11 .

Example 3:

According to the mass percentage, it is prepared from the following components: Zn 2%, Mn 0.5%, Gd 0.75%, Sr 0.15%, and the rest are Mg and unavoidable impurity elements. The specific preparation method is as follows:

S1) Weigh the material by mass percentage, the material is high-purity magnesium ingot, high-purity zinc ingot, Mg-5%Mn master alloy, Mg-25%Gd master alloy and Mg-20%Sr master alloy;

S2) Ingot smelting: smelting under the protection of high-purity argon, heating pure magnesium to 720°C for melting, then adding Mg-5%Mn master alloy and Mg-25%Gd master alloy in turn, and raising the temperature of the melt Heat it up to 740-760°C for 10-20 minutes, cool down to 720°C, add pure zinc and Mg-20%Sr master alloy, fully stir at 720°C for 5-10 minutes, refine and degas and remove surface scum, and cast to graphite mold;

S3) casting the alloy melt obtained in S2) into an ingot at 720° C. by gravity casting;

S4) Homogenization heat treatment: put the above-mentioned cast ingot in S3) in a vacuum heat treatment furnace protected by high-purity argon, first raise the temperature to 350°C at a heating rate of 5°C/min and keep it warm for 4h, and then heat at the same heating rate To 480 ℃ holding time for 12h, and then processed into extrusion billets;

S5) Hot extrusion: preheat the extruded billet at 400°C for 0.5-1h, apply molybdenum disulfide grease on the surface, and extrude through an extruder at an extrusion temperature of 400°C and an extrusion ratio of 16:1 ;

S6) Annealing treatment: the extruded material is kept at 250°C for 0.5h, and air-cooled.

The room temperature yield strength of the magnesium alloy obtained in this embodiment S6) is 152 MPa, the room temperature tensile strength is 242 MPa, and the room temperature elongation is 19%. After soaking in simulated body fluid for 480h, the weight loss rate is 0.309mm/year. The metallographic microstructure of the obtained magnesium alloy is shown in Figure 4; the TEM microstructure of the alloy is shown in Figure 8; the 3D morphology of the alloy after removing corrosion products after soaking in simulated body fluid for 480 hours is shown in Figure 12 .

Example 4:

According to the mass percentage, it is prepared from the following components: Zn 2%, Mn 0.35%, Gd 0.75%, Sr 0.3%, and the rest are Mg and unavoidable impurity elements. The specific preparation method is as follows:

S1) Weigh the material by mass percentage, the material is high-purity magnesium ingot, high-purity zinc ingot, Mg-5%Mn master alloy, Mg-25%Gd master alloy and Mg-20%Sr master alloy;

S2) Ingot smelting: smelting under the protection of high-purity argon, heating pure magnesium to 720°C for melting, then adding Mg-5%Mn master alloy and Mg-25%Gd master alloy in turn, and raising the temperature of the melt Heat it up to 740-760°C for 10-20 minutes, cool down to 720°C, add pure zinc and Mg-20%Sr master alloy, fully stir at 720°C for 5-10 minutes, refine and degas and remove surface scum, and cast to graphite mold;

S3) casting the alloy melt obtained in S2) into an ingot at 720° C. by gravity casting;

S4) Homogenization heat treatment: put the above-mentioned cast ingot in S3) in a vacuum heat treatment furnace protected by high-purity argon, first raise the temperature to 350°C at a heating rate of 5°C/min and keep it warm for 4h, and then heat at the same heating rate To 480 ℃ holding time for 12h, and then processed into extrusion billets;

S5) Hot extrusion: preheat the extrusion billet at 400°C for 0.5-1h, apply molybdenum disulfide grease on the surface, and extrude through an extruder at a temperature of 400°C and an extrusion ratio of 16:1 ;

S6) Annealing treatment: the extruded material is kept at 250°C for 0.5h, and air-cooled.

The room temperature yield strength of the magnesium alloy obtained in the embodiment S6) is 158 MPa, the room temperature tensile strength is 247 MPa, and the room temperature elongation is 20.5%. After soaking in simulated body fluid for 480 hours, the weight loss rate is 0.357mm/year. The metallographic microstructure of the obtained magnesium alloy is shown in Figure 5; the TEM microstructure of the alloy is shown in Figure 9; the 3D morphology of the alloy after immersion in simulated body fluid for 480 hours after removal of corrosion products is shown in Figure 13 .

The preparation method of a uniformly degradable medical magnesium alloy provided above has been introduced in detail. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation and application scope. To sum up, the contents of this specification should not be understood as limiting the application.

Certain terms are used, for example, in the description and claims to refer to particular components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not use the difference in name as a way to distinguish components, but use the difference in function of components as a criterion for distinguishing. As mentioned throughout the specification and claims, "comprising" and "comprising" are open-ended terms, so they should be interpreted as "comprising/including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred implementation mode for implementing the application, but the description is for the purpose of illustrating the general principle of the application, and is not intended to limit the scope of the application. The scope of protection of this application should be defined by the appended claims.

It should also be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a good or system comprising a set of elements includes not only those elements but also includes items not expressly listed. other elements of the product, or elements inherent in the commodity or system. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the article or system comprising said element.

It should be understood that the term "and/or" used herein is only an association relationship describing associated objects, which means that there may be three relationships, for example, A and/or B, which may mean that A exists alone, and A and B exist simultaneously. B, there are three situations of B alone. In addition, the character "/" in this article generally indicates that the contextual objects are an "or" relationship.

The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various Various other combinations, modifications and environments, and can be modified by the above teachings or the technology or knowledge in the related field within the scope of the application concept described herein. However, changes and changes made by those skilled in the art do not depart from the spirit and scope of the present application, and should all be within the protection scope of the appended claims of the present application.

Claims (10)

1. The preparation method of the medical magnesium alloy capable of being uniformly degraded is characterized by comprising the following steps:

s1) weighing each material according to the mass percent of the designed components, wherein the material contains Gd, and the mass percent of the Gd is less than 1%;

s2) smelting the materials weighed in the S1) under a protective atmosphere, refining, and finally casting into a cast ingot;

s3) homogenizing the ingot casting obtained in the S2);

s4) carrying out extrusion deformation treatment on the cast ingot treated in the S3) to obtain a magnesium alloy;

and S5) annealing the extruded magnesium alloy obtained in the step S4), and air-cooling to obtain the medical magnesium alloy with uniform corrosion characteristics and uniform degradation.

2. The method according to claim 1, wherein the matrix of the uniformly degradable medical magnesium alloy has a uniformly distributed α -Mg grain structure and Mg3Zn3Gd2 precipitated phases, wherein the α -Mg grain structure has a size of 8 to 15 μm; and the potential difference between the Mg3Zn3Gd2 precipitated phase and the magnesium alloy matrix is 0.13-0.14 v.

3. The method of claim 1, wherein the uniformly degradable medical magnesium alloy has a tensile strength at room temperature of: 229-247 MPa, and the yield strength is: 138-158 MPa, and the room temperature elongation is as follows: 19 to 28 percent; after the artificial body fluid is soaked in the simulated body fluid for 480 hours, the weight loss rate is 0.218-0.354 mm/year.

4. The method according to claim 1, wherein the mass percentages of the elements of the materials in S1) are as follows: 1.5 to 2.0% of Zn, mn:0.3 to 0.6%, gd: 0.45-0.79%, sr:0.15 to 0.3 percent, and the balance of Mg and inevitable impurity elements.

5. The method according to claim 4, wherein the sum of the mass percentages of the unavoidable impurity elements is <0.015%, and the unavoidable impurities are <0.005% of Fe, <0.005% of Ni, and <0.005% of Cu.

6. The method according to claim 1, wherein the specific process in S2) is:

firstly, preserving heat for 30-60 min at the temperature of 750-780 ℃, stirring for 5-10 min after materials are all melted, then cooling to 720-740 ℃, refining for 5-10 min, heating to 750-780 ℃ after refining, standing for 6-8 min, and cooling the melt to 700-720 ℃ for casting.

7. The method as claimed in claim 1, wherein the homogenization treatment in S3) adopts a two-stage homogenization heat treatment, and the process parameters are as follows: the temperature is 350-480 ℃, and the heat preservation time is 16-24 h.

8. The method as claimed in claim 1, wherein the extrusion deformation in S4) has a temperature of 400 ℃, an extrusion ratio of 16:1.

9. the method according to claim 1, wherein the temperature of the annealing treatment in S5) is 200-250 ℃ and the holding time is 0.5-1 h.

10. The medical magnesium alloy which is prepared by the method of any one of claims 1 to 9 and can be uniformly degraded is applied to the preparation of cardiovascular stents, medical bone nails and anastomosis nails.

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