CN110144505B - Degradable biomedical forged magnesium alloy and preparation method thereof - Google Patents
Degradable biomedical forged magnesium alloy and preparation method thereof Download PDFInfo
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- CN110144505B CN110144505B CN201910575677.0A CN201910575677A CN110144505B CN 110144505 B CN110144505 B CN 110144505B CN 201910575677 A CN201910575677 A CN 201910575677A CN 110144505 B CN110144505 B CN 110144505B
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/03—Making non-ferrous alloys by melting using master alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/06—Making non-ferrous alloys with the use of special agents for refining or deoxidising
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/04—Alloys based on magnesium with zinc or cadmium as the next major constituent
Abstract
The invention provides a degradable biomedical forged magnesium alloy, belonging to the field of degradable biomedical materials. A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 3.3 to 9% of Zn, 0.1 to 0.6% of Zr, 0.75 to 2% of Y, the mass ratio of Zn/Y is more than 4.38 and less than 6, and the balance is Mg. The magnesium alloy has good mechanical property, good corrosion resistance and good biocompatibility, is suitable for being used as bone repair materials such as porous magnesium alloy materials, plastic surgery materials, oral implantation materials, bone lamella bone nails and the like, and is particularly suitable for being used as cardiovascular stent materials and orthopedic repair materials.
Description
Technical Field
The invention belongs to the field of degradable biomedical materials, and particularly relates to a degradable biomedical forged magnesium alloy and a preparation method thereof.
Background
The biomedical magnesium alloy is an ideal biomedical metal implant material, and has the advantages in various aspects such as biomechanical compatibility, biocompatibility, biodegradability, economic applicability and the like, so that the biomedical magnesium alloy is generally concerned by extensive biomaterial researchers at home and abroad in recent years. However, the biomedical magnesium alloy has the problem of over-quick corrosion in the physiological environment of a human body, so that the biomedical magnesium alloy loses mechanical integrity and mechanical property effectiveness before bone healing or blood vessel blockage recovery, treatment failure is caused, and other adverse reactions can be caused. Therefore, the biomedical magnesium alloy with high strength, high toughness and high corrosion resistance is developed as soon as possible and is applied to clinical work tasks as soon as possible.
Patent document CN107541632A discloses a biomedical Mg-Zn-Zr magnesium alloy and a preparation method thereof. The alloy comprises the following components in percentage by mass: zn: 0.8 to 3.0%, Zr: 0.4 to 0.8 percent, and the balance of Mg and inevitable impurities. According to the invention, alloy elements Zn and Zr are added into the magnesium alloy, so that the mechanical property and the corrosion resistance of the magnesium alloy are improved; meanwhile, Zn and Zr belong to elements harmless to human bodies, so that the alloy is not harmful to human health after being degraded by human bodies. The preparation method of the biomedical Mg-Zn-Zr magnesium alloy obtains the biomedical magnesium alloy through raw material smelting, casting and solution treatment, and has the advantages that the precipitated phases of the Mg-Zn-Zr magnesium alloy are less, so that galvanic corrosion is favorably reduced; the uniformity of the structure is improved after solid solution, and the mechanical property of the alloy is effectively improved. However, the biomedical Mg-Zn-Zr magnesium alloy has poor strength and general corrosion resistance.
Patent document No. CN104195483A discloses a heat treatment process for improving corrosion resistance of Mg-Zn-Y-Zr magnesium alloy, and particularly relates to a heat treatment process capable of remarkably improving corrosion resistance of magnesium alloy and simultaneously keeping higher yield strength and tensile strength of the alloy. Tightly wrapping the deformed magnesium alloy with an aluminum foil, carrying out two-stage solution treatment, keeping the temperature for 2-4 hours at 300-330 ℃, heating to 400-450 ℃ along with a furnace, keeping the temperature for 2-4 hours at the temperature, and then carrying out water quenching and cooling to room temperature. The invention can obviously improve the corrosion resistance of the magnesium alloy, solves the problem of poor corrosion resistance of the magnesium alloy, simultaneously keeps higher yield strength and tensile strength of the alloy, and widens the practical engineering application of the magnesium alloy. According to the invention, through two-stage solution treatment, the corrosion resistance of the Mg-Zn-Y-Zr magnesium alloy is improved, but the corrosion resistance has a great space for improving, and the strength performance is required to be improved.
Disclosure of Invention
In view of the above, a technical problem to be solved by the present invention is to provide a degradable biomedical wrought magnesium alloy, which has good mechanical properties, good corrosion resistance, and good biocompatibility, and is suitable for being used as a porous magnesium alloy material, an orthopedic material, an oral implant material, a bone plate and bone nail and other bone repair materials, especially suitable for being used as a cardiovascular stent material and an orthopedic repair material.
The invention also provides a method for preparing the degradable biomedical forged magnesium alloy.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 3.3 to 9% of Zn, 0.1 to 0.6% of Zr, 0.75 to 2% of Y, the mass ratio of Zn/Y is more than 4.38 and less than 6, and the balance is Mg.
Preferably, the degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 3.6 to 5.6 percent of Zn, 0.1 to 0.39 percent of Zr and 0.75 to 1 percent of Y, wherein the mass ratio of Zn to Y is more than 4.38 and less than 6, and the balance is Mg.
Preferably, the degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 4.45% of Zn, 0.38% of Zr and 0.75% of Y, wherein the mass ratio of Zn to Y is more than 4.38 and less than 6, and the balance is Mg.
Preferably, the degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 6.5-7.8% of Zn, 0.41-0.6% of Zr and 1.17-1.72% of Y, wherein the mass ratio of Zn to Y is more than 4.38 and less than 6, and the balance is Mg.
The preparation method of the degradable biomedical forged magnesium alloy comprises the following steps:
(1) material preparation: putting Zn particles and an intermediate alloy into a crucible according to a ratio, wherein the intermediate alloy is ZK60 and Mg-30% of Y;
(2) a melting step: introducing argon into the smelting furnace to evacuate air, heating the smelting furnace, preheating a crucible to 660-750 ℃, and melting the magnesium alloy ingredients;
(3) and (3) refining: adding a refining agent into the melted magnesium ingot for refining;
(4) stirring: stirring the refined magnesium ingot to completely melt the magnesium alloy ingredients;
(5) and (3) a production step: pouring, cooling, forging a plate blank, and rolling to obtain the biomedical magnesium alloy.
Preferably, the refining agent consists of the following mass percentComprises the following components: 55-65% of CaO and 30-40% of CaF2And 1-5% Ca (OH)2。
Preferably, the mass of the refining agent is 0.5-1.2% of the total mass of the magnesium alloy.
Preferably, the stirring conditions are: forward rotation at 100 r/min-200 r/min for 10-15 min, and backward rotation at 100 r/min-200 r/min for 10-15 min.
The invention relates to Mg-Zn-Zr-Y magnesium alloy, which is known in the field, Y has high solid solubility in Mg, and the Mg-Y alloy has good aging strengthening capability. In the prior art, the comprehensive performance of the alloy is improved by adding Y element into the magnesium alloy, for example, Chinese invention patent with the patent number of ZL200410081258.5, wherein the content of Y is not more than 2%; reference can also be made to the Chinese invention patent with the patent number ZL200710011505.X, wherein Zn/Y satisfies 6-15, the content of Zn is far more than that of Y, and the content of Y is not more than 5%. Reference may also be made to the chinese patent application having application number 201310417034.6, wherein the content of Y does not exceed 1.0%. The tensile strength and yield strength of the magnesium alloy are indeed improved by adding the Y element in the alloys, but the corrosion resistance of the magnesium alloy is not listed as an attention index and is not paid enough attention and research, so that the magnesium alloy needs to be researched and acquired by continuing creative efforts of a person skilled in the art if the magnesium alloy is to be developed into biomedical implant materials.
Corresponding to the above common knowledge in the field, magnesium alloy is used as biomedical material to implant in vivo, because the corrosion resistance of the magnesium alloy can not meet the use requirement, the corrosion rate is too fast to cause the vascular stent to lose mechanical properties prematurely, a large amount of hydrogen is generated during the degradation of the magnesium alloy to be unfavorable for tissue healing, and the expanded application is not seen so far, and the theories and practices obstruct the research and experiment of the technicians in the field on the use of the magnesium alloy as the biomedical material to a certain extent.
The corrosion resistance of magnesium alloy has been also tried to be focused by a very small number of researchers in the field, such as royal and the like (royal, jacobian, october and the like. the research on the corrosion resistance of biodegradable magnesium alloy has been advanced [ J ] materials report, 2014, 28 (24): 267-271), and the research results of the researchers have been considered as follows: the finer the grain size, the better the corrosion resistance of the alloy, but the mechanism of influence on its corrosion resistance is still under investigation. Researchers of Korean soldiers and the like (Korean soldiers, Jiachang Jian, Zhao soldiers and the like, research on corrosion performance of Mg-2Y-xZn-0.4Zr alloy for degradable vascular stents [ J ] casting technology, 2017 (05): 29-31) preliminarily find that the addition of Zn element in Mg-Zn-Zr-Y magnesium alloy leads the refinement of alloy crystal grains to have a certain effect on the improvement of the corrosion resistance of the alloy, but is not a main factor for improving the corrosion resistance. Further, it is pointed out that the corrosion resistance of the alloy is mainly determined by phase W and phase I, which improve the corrosion resistance of the alloy, while phase W tends to adversely affect the corrosion resistance of the alloy. Therefore, theoretically, if the I phase distribution can be increased and the W phase distribution can be decreased, the corrosion resistance of Mg-Zn-Zr-Y magnesium alloy can be improved, but how to realize this assumption is still in the research stage, and there is no reliable reference. On the basis of the technology, the inventor group is researched and explored for more than two years, the distribution of the I phase is determined by the mass ratio of Zn/Y and the content of Y, the ideal crystal phase distribution cannot be obtained by singly changing the mass ratio of Zn/Y or the content of Y, and the research of the inventor finds that a theory with great reference value is provided for further promoting the research of Mg-Zn-Zr-Y magnesium alloy in the aspect of medical implant materials.
Compared with the prior art, the invention has the following beneficial effects:
according to the technical scheme, the degradable biomedical forging magnesium alloy is Mg-Zn-Zr-Y magnesium alloy, and has higher room-temperature mechanical property compared with other magnesium alloys. Wrought Mg-5.45Zn-0.38Zr alloy free of Y element and having a major phase composition of Mg0.97Zn0.03Phase and alpha-Mg matrix, Zr element does not form phase. Quasi-crystalline I phase (Mg) is detected in the XRD diffraction spectrum of the forged Mg-4.45Zn-0.38Zr-0.75Y alloy3YZn6) Other than the diffraction peak (b), no other phase was found. Quasicrystal I phase (Mg) in Mg-Zn-Y- (Zr) alloy3YZn6) The formation of (A) is strictly dependent on the Zn/Y mass ratio in the alloy, and XRD phase analysis shows that when the Zn/Y mass ratio in the alloy is strictly dependent on the Zn/Y mass ratio in the alloy, the formation of (A) is strictly dependent on the Zn/Y mass ratio in the alloyWhen the Zn/Y mass ratio is more than 4.38 (the Zn/Y mass ratio of the Mg-4.45Zn-0.38Zr-0.75Y alloy is 5.93), the phase composition becomes an alpha-Mg + quasicrystal I phase (Mg-4.45 Zn-0.38Zr-0.75Y alloy)3YZn6). When the Zn/Y ratio varies between 1.10 and 4.38, the main phases in the alloy are the I-phase, W-phase and a-Mg matrices. When Zn/Y is less than 1.10, the main phases of the alloy are W-phase and a-Mg matrix. Tensile test results show that the strength of the alloy increases with increasing I-phase number when the Y content varies between 0.75 and 1.0 wt.%. The alloy has high strength because the volume fraction of I-phase in the alloy reaches the maximum value when the content of Y is changed between 1.17 and 1.72 wt.%. Therefore, the improvement of the strength of Mg-Zn-Zr-Y magnesium alloy is mainly dependent on the strengthening effect of the quasicrystalline phase I-phase particles. When the content of Zn in the Mg-Zn binary alloy is up to 5wt.%, the alloy shows grain boundary, solid solution and secondary phase strengthening, thereby improving the corrosion resistance and mechanical strength of the alloy. The corrosion of the magnesium alloy is more uniform after the Y element is added into the magnesium alloy, and the body fluid corrosion resistance of the magnesium alloy is improved after the Y element is added into the Mg-Zn series alloy. The corrosion behavior of the Mg-Zn-Zr-Y alloy in an SBF simulated body fluid solution is researched, and the result shows that the corrosion resistance of the magnesium alloy can be obviously influenced by the second phase (quasicrystal phase I-phase) and the Zn content in the Mg-Zn-Zr-Y alloy.
According to the characteristics of the raw materials of the magnesium alloy, the magnesium alloy with excellent mechanical properties is prepared by adopting fewer working procedures and simpler industrial control conditions. The preparation method provided by the invention has the advantages that the raw materials are melted and then refined to remove impurities, and the refining agent is improved and optimized by combining the component characteristics of the invention. The refining agent with the brand number of RJ-4, RJ-5 or MJL-J00 and the like is mostly adopted in the existing magnesium alloy refining, although the refining agent has certain effect on the magnesium alloy refining, the refining effect is general for the magnesium alloy with specific composition, so that the impurity removal and purification of the molten liquid are not thorough, and the mechanical property is seriously reduced, therefore, the refining agent develops the following components in percentage by mass: 55-65% of CaO and 30-40% of CaF2And 1-5% Ca (OH)2The refining agent has the advantages of wide and easily obtained raw material sources and simple preparation, and the magnesium alloy obtained by adopting the refining agent has excellent mechanical properties. In addition, the invention explores and optimizes the stirring condition of the refined melt, so that a new super-grade alloy does not need to be introducedThe sound equipment or the magnetic field can also realize good flowing and diffusion of each component, reduce the thickness of the diffusion layer, reduce component segregation and further remove gas and impurities. In general, the method is simple and easy to control, and the used equipment is modern general equipment, needs less manpower and material resources, and is suitable for large-scale production.
The degradable biomedical forging magnesium alloy is implanted into a body as a biomedical material, has good mechanical property, good corrosion resistance and good biocompatibility, is suitable for being used as a bone repair material such as a porous magnesium alloy material, an orthopedic material, an oral implant material, a bone plate and bone nail and the like, and is particularly suitable for being used as a cardiovascular stent material.
Drawings
FIG. 1: the invention discloses a microstructure picture of a forged Mg-4.45Zn-0.38Zr-0.75Y alloy;
FIG. 2: the room temperature tensile stress-strain curve diagram of the forged Mg-4.45Zn-0.38Zr-0.75Y alloy is shown;
FIG. 3: potentiodynamic polarization curves of pure magnesium, forged Mg-Zn-Zr alloy and forged Mg-4.45Zn-0.38Zr-0.75Y alloy of the invention in SBF simulated solution, wherein: and 1 is a passivation inflection point.
Detailed Description
In order to better understand the present invention, the following examples are further provided to clearly illustrate the contents of the present invention, but the contents of the present invention are not limited to the following examples. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without one or more of these specific details.
Example 1
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 4.1% of Zn, 0.23% of Zr and 0.93% of Y, wherein the mass ratio of Zn to Y is 4.39, and the balance is Mg.
The preparation method of the degradable biomedical forged magnesium alloy comprises the following steps:
(1) material preparation: putting Zn particles and an intermediate alloy into a crucible according to the proportion, wherein the intermediate alloy is ZK60 and Mg-30% of Y;
(2) a melting step: introducing argon into the smelting furnace to evacuate air, heating the smelting furnace, preheating a crucible to 660 ℃, and melting the magnesium alloy ingredients;
(3) and (3) refining: adding a refining agent into the melted magnesium ingot for refining;
(4) stirring: stirring the refined magnesium ingot to completely melt the magnesium alloy ingredients;
(5) and (3) a production step: pouring, cooling, forging a plate blank, and rolling to obtain the biomedical magnesium alloy.
The refining agent comprises the following components in percentage by mass: 55% CaO, 40% CaF2And 5% Ca (OH)2。
The mass of the refining agent is 0.5 percent of the total mass of the magnesium alloy.
The stirring conditions are as follows: stirring at 100r/min for 15min, and stirring at 200r/min for 10 min.
Example 2
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 4.45% of Zn, 0.38% of Zr and 0.75% of Y, wherein the mass ratio of Zn to Y is 5.93, and the balance is Mg.
The preparation method of the degradable biomedical forged magnesium alloy comprises the following steps:
(1) material preparation: putting Zn particles and an intermediate alloy into a crucible according to the proportion, wherein the intermediate alloy is ZK60 and Mg-30% of Y;
(2) a melting step: introducing argon into the smelting furnace to evacuate air, heating the smelting furnace, preheating a crucible to 700 ℃, and melting the magnesium alloy ingredients;
(3) and (3) refining: adding a refining agent into the melted magnesium ingot for refining;
(4) stirring: stirring the refined magnesium ingot to completely melt the magnesium alloy ingredients;
(5) and (3) a production step: pouring, cooling, forging a plate blank, and rolling to obtain the biomedical magnesium alloy.
The refining agent comprises the following components in percentage by mass: 60% of CaO, 35% of CaF2And 5% Ca (OH)2。
The mass of the refining agent is 0.8 percent of the total mass of the magnesium alloy.
The stirring conditions are as follows: stirring at 150r/min for 12min, and then at 130r/min for 15 min.
Example 3
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 5.6% of Zn, 0.1% of Zr and 1.26% of Y, wherein the mass ratio of Zn to Y is 4.44, and the balance is Mg.
The preparation method of the degradable biomedical forged magnesium alloy comprises the following steps:
(1) material preparation: putting Zn particles and an intermediate alloy into a crucible according to the proportion, wherein the intermediate alloy is ZK60 and Mg-30% of Y;
(2) a melting step: introducing argon into the smelting furnace to evacuate air, heating the smelting furnace, preheating a crucible to 720 ℃, and melting the magnesium alloy ingredients;
(3) and (3) refining: adding a refining agent into the melted magnesium ingot for refining;
(4) stirring: stirring the refined magnesium ingot to completely melt the magnesium alloy ingredients;
(5) and (3) a production step: pouring, cooling, forging a plate blank, and rolling to obtain the biomedical magnesium alloy.
The refining agent comprises the following components in percentage by mass: 62% CaO, 37% CaF2And 1% Ca (OH)2。
The mass of the refining agent is 1.0 percent of the total mass of the magnesium alloy.
The stirring conditions are as follows: stirring at 180r/min for 10min, and then at 160r/min for 12 min.
Example 4
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 5.1% of Zn, 0.6% of Zr and 1% of Y, wherein the mass ratio of Zn to Y is 5.1, and the balance is Mg.
The preparation method of the degradable biomedical forged magnesium alloy comprises the following steps:
(1) material preparation: putting Zn particles and an intermediate alloy into a crucible according to the proportion, wherein the intermediate alloy is ZK60 and Mg-30% of Y;
(2) a melting step: introducing argon into the smelting furnace to evacuate air, heating the smelting furnace, preheating a crucible to 750 ℃, and melting the magnesium alloy ingredients;
(3) and (3) refining: adding a refining agent into the melted magnesium ingot for refining;
(4) stirring: stirring the refined magnesium ingot to completely melt the magnesium alloy ingredients;
(5) and (3) a production step: pouring, cooling, forging a plate blank, and rolling to obtain the biomedical magnesium alloy.
The refining agent comprises the following components in percentage by mass: 65% CaO, 32CaF2And 3Ca (OH)2。
The mass of the refining agent is 1.2% of the total mass of the magnesium alloy.
The stirring conditions are as follows: stirring at 200r/min for 10min, and then at 100r/min for 15 min.
Example 5
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 6.5% of Zn, 0.41% of Zr and 1.17% of Y, wherein the mass ratio of Zn to Y is 5.56, and the balance is Mg.
Referring to example 2, the preparation method of the degradable biomedical forged magnesium alloy of the embodiment is different from example 2 in that:
the refining agent comprises the following components in percentage by mass: 65% CaO, 30% CaF2And 5% Ca (OH)2。
The mass of the refining agent is 0.6 percent of the total mass of the magnesium alloy.
Example 6
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 3.6% of Zn, 0.55% of Zr and 0.8% of Y, wherein the mass ratio of Zn to Y is 4.5, and the balance is Mg.
Referring to example 2, the preparation method of the degradable biomedical forged magnesium alloy of the embodiment is different from example 2 in that:
the refining agent comprises the following components in percentage by mass: 58% CaO, 40% CaF2 and 2% Ca (OH) 2.
The mass of the refining agent is 0.7 percent of the total mass of the magnesium alloy.
Example 7
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 9% of Zn, 0.39% of Zr and 1.97% of Y, the mass ratio of Zn to Y being 4.57, and the balance being Mg.
The preparation method of the degradable biomedical forged magnesium alloy in the embodiment refers to the embodiment 2.
Example 8
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 7.8% of Zn, 0.15% of Zr and 1.72% of Y, wherein the mass ratio of Zn to Y is 4.53, and the balance is Mg.
The preparation method of the degradable biomedical forged magnesium alloy in the embodiment refers to the embodiment 2.
Example 9
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 3.3% of Zn, 0.49% of Zr and 0.75% of Y, wherein the mass ratio of Zn to Y is 4.40, and the balance is Mg.
The preparation method of the degradable biomedical forged magnesium alloy in the embodiment refers to the embodiment 2.
Example 10
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 8.3% of Zn, 0.52% of Zr and 1.57% of Y, wherein the mass ratio of Zn to Y is 5.29, and the balance is Mg.
The preparation method of the degradable biomedical forged magnesium alloy in the embodiment refers to the embodiment 2.
Example 11
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 5.9% of Zn, 0.31% of Zr and 1.01% of Y, wherein the mass ratio of Zn to Y is 5.84, and the balance is Mg.
The preparation method of the degradable biomedical forged magnesium alloy in the embodiment refers to the embodiment 2.
Comparative example 1
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 4.45% of Zn, 0.38% of Zr and 1.02% of Y, wherein the mass ratio of Zn to Y is 4.36, and the balance is Mg. The preparation method of the comparative example degradable biomedical forged magnesium alloy is the same as that of example 2.
Comparative example 2
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: 4.45% of Zn, 0.38% of Zr and 0.74% of Y, wherein the mass ratio of Zn to Y is 6.01, and the balance is Mg. The preparation method of the comparative example degradable biomedical forged magnesium alloy is the same as that of example 2.
Comparative example 3
A degradable biomedical forged magnesium alloy comprises the following components in percentage by mass: the weight percentage composition is as follows: 3.0% of Zn, 0.38% of Zr and 0.67% of Y, wherein the mass ratio of Zn to Y is 4.5, and the balance is Mg.
The preparation method of the comparative example degradable biomedical forged magnesium alloy is the same as that of example 2.
Comparative example 4
The degradable biomedical forged magnesium alloy has the same mass percentage composition as that of the magnesium alloy in the embodiment 2, and the preparation method is different from that of the magnesium alloy in the embodiment 2 in that:
and (3) refining: adding a refining agent into the melted magnesium ingot for refining, wherein the refining agent comprises the following components in percentage by mass: 65% CaO and 35% CaF2。
Comparative example 5
The degradable biomedical forged magnesium alloy has the same mass percentage composition as that of the magnesium alloy in the embodiment 2, and the preparation method is different from that of the magnesium alloy in the embodiment 2 in that:
stirring: stirring the refined magnesium ingot to completely melt the magnesium alloy ingredients;
the stirring conditions are as follows: stirring at 300r/min for 30 min.
Evaluation of the effects:
1. the microstructure, mechanical properties and corrosion resistance of the magnesium alloy obtained in example 2 of the present invention were tested.
1) And (3) microscopic structure observation: cutting a forged magnesium alloy sample into small cylinders with the diameter of 12mm multiplied by 10mm by spark lines, sequentially performing water grinding by using abrasive paper of 240#, 600#, 1000#, 2000#, 3000# and 4000#, wherein the abrasive paper is sequentially ground in the same direction, rotating the sample by 90 degrees when the scratches are in the same direction, continuously performing water grinding, and then replacing finer abrasive paper to repeat the process for 2-3 times. And after the 4000# abrasive paper is water-milled, spraying polishing liquid on the sample on a polishing machine, and polishing until the surface is bright and has no scratch.
Corrosion of forged magnesium alloy: picric acid is used as a corrosive agent, and the corrosion time is 15-20 s. The picric acid is prepared by mixing 2g of picric acid, 10mL of glacial acetic acid, 20mL of distilled water and 25mL of ethanol. And immediately cleaning and blow-drying the bitter acid by absolute ethyl alcohol after corrosion, then observing whether the metallographic specimen is well corroded on a DX708D type metallographic microscope, and finally observing the microstructure of the metallographic specimen by using the metallographic microscope and taking a picture. The results are shown in FIG. 1.
2) And (3) testing mechanical properties: the mechanical properties of magnesium alloys are mainly reflected by testing the tensile strength, yield strength and elongation of the alloy. The tensile strength, yield strength and elongation of the alloy are tested by adopting a CMT5305 type microcomputer control electronic universal testing machine, the tensile test standard is executed according to GB/T228.1-2010, and the tensile rate is 5.0 mm/min. The preparation process of the alloy tensile sample comprises the following steps: firstly, cutting an alloy standard tensile sample shown in FIG. 2 by using a wire cut electrical discharge machine, wherein the thickness of the sample is 5mm, and then sequentially polishing the surface of the sample by using 240#, 650#, 1000# and 2000# sandpaper until the sample has no cutting edges and the surface is smooth. To ensure the accuracy of the experimental results, 5 replicates were tested per component and the experimental results averaged. The results are shown in table 1 and fig. 2.
3) Corrosion resistance:
preparation of corrosive media
Analytically pure chemical reagents and distilled water are adopted to prepare 1000mLSBF simulated body fluid in a constant temperature water bath box (37 +/-0.5) DEG C, the components of the simulated body fluid are shown in Table 2, and HCl and NaOH are adopted to adjust the initial pH value of the SBF simulated body fluid to be 7.4. Using chromic acid solution (200 g/LCr)2O3+10g/LAgNO3+ distilled water) to clean the corrosion products.
TABLE 2 chemical composition (g/l) of SBF simulated body fluids
The configuration method comprises the following steps:
liquid A: na (Na)2HPO4•12H2O0.06g、KH2PO40.06g、MgSO4•7H2O0.06g, glucose 1.00g, NaCl8.00g and deionized water 750 mL;
b, liquid B: CaCl20.14g、KCl0.4g、MgCl2•6H2O0.10g and 100mL of deionized water.
A configuration step:
1) slowly adding the solution B into the solution A.
2) 0.35g of NaHCO3Dissolved in 10mL of deionized water at 37 ℃.
3) With several drops of NaHCO3The solution dissolved 0.02g of phenol red.
4) Transferring the 2) 3) solution into 1).
5) And (4) metering the volume to 1000mL by using deionized water, fully and uniformly mixing, and placing in a refrigerator at 4 ℃ for supercooling.
6) Filtering, sterilizing, packaging with 500mL vials, and refrigerating.
The corrosion resistance of the biomedical magnesium alloy can also be observed and researched by an electrochemical experiment. The electrochemical testing apparatus was an electrochemical workstation model CHI 660D. In the test process, a three-electrode system is adopted, the working electrode is a magnesium alloy sample (pure magnesium and forged Mg-Zn-Zr/-Y magnesium alloy), the reference electrode is a saturated calomel electrode, and the auxiliary electrode is a Pt electrode.
An electrochemical test sample preparation method comprises the following steps: a test sample is made into a square body with the size of 10mm multiplied by 2mm by using a wire cut electric discharge machine, other faces of the square body are wrapped and sealed by epoxy resin, only a test face with the exposed area of 1cm2 is exposed, the surface is subjected to water grinding by 240#, 600#, 1200#, 2000#, 3000# abrasive paper before the experiment, the surface is polished to be bright and free of scratches, the surface of the test sample is sequentially cleaned for 10 minutes in an ultrasonic cleaning machine by using acetone and absolute ethyl alcohol, then the test sample is dried by using cold air and then subjected to the experiment, and three parallel test samples are tested by each component. The corrosion medium is SBF simulated body fluid at 25 +/-1 ℃.
The method for testing the potentiodynamic polarization curve is a potentiodynamic scanning method. The scanning range of the potentiodynamic polarization curve is +/-0.1V, the scanning speed is 5mV/s, 3 parallel samples are measured in each group, the average value of 3 measurements is taken as a result, and the electrochemical polarization curve (also called Tafel curve) is drawn according to experimental data.
The results are shown in table 3 and fig. 3.
4) And (4) analyzing results:
referring to fig. 1, as can be seen from the microstructure of the forged Mg-4.45Zn-0.38Zr-0.75Y alloy, the grains of the alloy have a grain distribution morphology in which small grains surround large grains, because during the forging process, the grain boundary part is broken and recombined, and meanwhile, because the second phase at the grain boundary is slowly diffused during the forging deformation process, the local morphology in which small grains surround large grains is formed, and these regions hinder the deformation of large grains during the plastic deformation of the magnesium alloy, and improve the strength of the magnesium alloy. It can also be seen that the coarse second phase aggregates at the grain boundary interface, while some fine second phase particles appear to be distributed in clusters within the matrix. The average grain size of the Mg-4.45Zn-0.38Zr-0.75Y alloy measured by an intercept method is 90.47 mu m, which shows that the Y element has a certain effect on the grain refinement of the alloy.
② the tensile test results of the forged Mg-Zn-Zr-Y alloy are shown in Table 1.
TABLE 1 tensile test results for as-forged Mg-Zn-Zr-Y alloys
From Table 1, the tensile strength of the forged Mg-4.45Zn-0.38Zr-0.75Y alloy reaches 298.6MPa, the yield strength reaches 219.4MPa, the elongation reaches 16.2 percent, and the mechanical property requirement of the biomedical magnesium alloy material is met. Along with the addition of Zn, Zr and Y elements, the microstructure of the forged magnesium alloy is refined, so that the mechanical property of the forged Mg-4.45Zn-0.38Zr-0.75Y alloy is greatly improved.
The room temperature tensile stress-strain curve of the as-forged Mg-Zn-Zr-Y alloy is shown in FIG. 2.
According to the Hall-Petch formula σs=σ0+kd-1/2The value of the constant k is related to the number of alloy sliding systems, the k values of the face-centered cubic structure and the body-centered cubic structure are both smaller than those of the close-packed hexagonal structure, Mg belongs to the close-packed hexagonal structure, and the k value is larger, so that the effect of grain refinement on enhancing the strength of the magnesium alloy is obvious theoretically. In this experiment, the morphology, volume fraction and distribution of the second phase of the alloy are decisive for the properties of the alloy. In the metallographic structure of the forged Mg-4.45Zn-0.38Zr-0.75Y alloy, Zr element is added to refine the crystal grains of the alloy, and simultaneously, the Zn element added to Zn and Y element promotes the start of a slip system and the uniform distribution of a quasicrystal I phase so as to improve the performance of the alloy, and the elongation is reduced mainly due to the quasicrystal I phase (Mg) in the alloy3YZn6) The mechanical property requirement of the biomedical magnesium alloy is still met due to the action.
③ the zeta potential polarization curve of the Mg-Zn-Zr-Y magnesium alloy in the forging state in the SBF simulation solution (compared with pure magnesium and Mg-Zn-Zr alloy in the forging state) is shown in figure 3.
The microcellular effect of magnesium alloys can be reflected by electrochemical corrosion, and FIG. 3 is an electrochemical polarization curve of typical as-forged Mg-Zn-Zr-Y alloys and pure magnesium. The polarization curves of the magnesium alloy conform to the Tafel rule, so that the self-corrosion current density Icorr and the self-corrosion potential Ecorr of the alloy can be obtained by fitting the polarization curves in the Tafel mode by using Corrview software, and the results are shown in Table 3.
TABLE 3 polarization curve fitting results for pure magnesium and as-forged Mg-Zn-Zr-Y alloys
The corrosion rate v and the corrosion current density of the electrode satisfy Faraday's law,
in the formula (I), the compound is shown in the specification,υas corrosion rate, g.m-2·h-1；IcorrIs self-etching current density, μ A-cm-2(ii) a M is the atomic mass of the metal, g.mol-1(ii) a n is the amount of the electron-transferring substance in the reaction, mol; f is the Faraday constant, 96484C or 26.8A · h.
As can be seen from the formula (1.1), the corrosion rate of the alloyυAnd self-corrosion current density IcorrIs proportional, therefore can use IcorrTo characterize the corrosion rate of the alloyυThe size of (2).
As can be seen from FIG. 3, there is a distinct "passivation inflection point" on both the pure magnesium and the as-forged Mg-Zn-Zr-Y alloy in the anode region, but the Mg-Zn-Zr-Y corrosion current rises very slowly with increasing corrosion potential before the "passivation inflection point" of the as-forged Mg-Zn-Zr-Y alloy; after a "passivation inflection" of the as-forged Mg-Zn-Zr-Y alloy, the Mg-Zn-Zr-Y corrosion current increases dramatically over a small range of corrosion potential changes, indicating that the corrosion product layer of the Mg-Zn-Zr-Y alloy begins to crack. As can be seen from Table 3, the self-corrosion current density I of the as-forged Mg-Zn-Zr-Y alloycorr2.512, self-Corrosion Current Density I of as-forged Mg-Zn-Zr alloycorr4.762, the self-corrosion currents of the Mg-Zn-Zr-Y alloys are all lower than that of pure magnesium, indicating that the Mg-Zn-Zr-Y alloys are more corrosion resistant than pure magnesium, while the self-corrosion current densities of the Mg-Zn-Zr-Y alloys are the lowest, indicating that the Mg-Zn-Zr-Y alloys have better corrosion resistance than the Mg-Zn-Zr.
2. The mechanical properties and corrosion resistance of the magnesium alloys obtained in comparative examples 1 to 5 of the present invention were measured, and the results are shown in tables 4 and 5.
TABLE 4 tensile test results of as-forged magnesium alloys
TABLE 5 polarization curve fitting results for as-forged magnesium alloys
As can be seen from the data in tables 1 and 4, the Zn/Y mass ratio and the content of Y element both have significant effects on the mechanical properties of the magnesium alloy of the present invention, and when the Zn/Y mass ratio is 4.36 (less than 4.38) (comparative example 1), the tensile strength of the magnesium alloy obtained by the preparation method according to the present invention is increased, but the yield strength and elongation are decreased. When the Zn/Y mass ratio was 6.01 (more than 6) (comparative example 2), the tensile strength, yield strength and elongation of the resulting magnesium alloy were all significantly reduced. Comparative example 3 taking the Zn content of 3.0% and simultaneously decreasing the Y content to 0.67% based on the composition of the magnesium alloy of the present invention and having a Zn/Y mass ratio of 4.5 (more than 4.38 and less than 6), the result showed that the tensile strength of the resulting magnesium alloy was substantially unchanged and the yield strength and elongation were significantly decreased. Comparative example 4 the composition of the refining agent was changed, and the Ca (OH) component of example 2 was removed2The mechanical properties of the obtained magnesium alloy are obviously reduced. Comparative example 5 the stirring conditions were changed, the mechanical properties of the obtained magnesium alloy were reduced, the rationality of the design of the stirring conditions of the present invention was shown, and the stirring conditions of the present invention were advantageous for improving the mechanical properties of the magnesium alloy of the present invention.
As can be seen from the data in tables 3 and 5, the self-corrosion current density of the as-forged magnesium alloy varies depending on the content of the alloy components. Although the data in Table 3 show that the addition of Y element is beneficial to the reduction of the self-corrosion current density, i.e. the improvement of the corrosion resistance of the magnesium alloy, in the magnesium alloy of the present invention, although the Y element is added, the corrosion resistance is reduced when the Zn/Y mass ratio is less than 4.38 (comparative example 1), and simultaneously, when the Y element is added, the Zn/Y mass ratio is more than 6, the improvement of the corrosion resistance is still not affected, and the corresponding performance is also reduced (comparative example 2). Comparative example 3 has both reduced Zn and Y contents and a Zn/Y mass ratio of 4.5 (more than 4.38 and less than 6) as compared with example 2, and the resulting magnesium alloy shows a reduced tendency of self-corrosion current density due to the reduced mechanical properties of the magnesium alloy and reduced corrosion resistance. Comparative example 4 compared to example 2, the corrosion resistance of the resulting magnesium alloy was reduced by changing the refining conditions, i.e., changing the composition of the refining agent, because: the refining is not thorough, resulting in a significant reduction in the tensile strength, yield strength and elongation of the magnesium alloy. And the comparative example 5 changes the stirring condition, so that the mechanical property of the obtained magnesium alloy is reduced, and the corrosion resistance is reduced.
In conclusion, the Mg-Zn-Zr-Y magnesium alloy disclosed by the invention is reasonable in component composition, the preparation method is scientific and rigorous, the tensile strength of the obtained magnesium alloy is 296-305 MPa, the yield strength is 198.4-218.5 MPa, the elongation is 16.2-18.2%, and the self-corrosion current density is 2.423-2.512 x 10-6A/cm2。
Although specific embodiments of the invention have been described above, it will be understood by those skilled in the art that the specific embodiments described are illustrative only and are not limiting upon the scope of the invention, and that equivalent modifications and variations can be made by those skilled in the art without departing from the spirit of the invention, which is to be limited only by the appended claims.
Claims (4)
1. A degradable biomedical forged magnesium alloy is characterized in that: the components by mass percentage are as follows: 3.3 to 4.45% of Zn, 0.1 to 0.23% of Zr, 0.75 to 0.93% of Y, the mass ratio of Zn/Y is more than 4.38 and less than 6, and the balance is Mg,
the preparation method of the degradable biomedical forged magnesium alloy comprises the following steps:
(1) material preparation: putting Zn particles and an intermediate alloy into a crucible according to the proportion, wherein the intermediate alloy is ZK60 and Mg-30% of Y;
(2) a melting step: introducing argon into the smelting furnace to evacuate air, heating the smelting furnace, and preheating a crucible to 660-750 ℃ to melt magnesium alloy ingredients;
(3) and (3) refining: adding a refining agent into the melted magnesium ingot for refining, wherein the refining agent comprises the following components in percentage by mass: 55-65% of CaO and 30-40% of CaF2And 1-5% Ca (OH)2；
(4) Stirring: stirring the refined magnesium ingot to completely melt the magnesium alloy ingredients;
(5) and (3) a production step: pouring, cooling, forging a plate blank, and rolling to obtain the biomedical magnesium alloy
2. The degradable biomedical wrought magnesium alloy of claim 1, wherein: 3.6 to 4.45 percent of Zn, 0.1 to 0.23 percent of Zr, 0.75 to 0.93 percent of Y, the mass ratio of Zn to Y is more than 4.38 and less than 6, and the balance is Mg.
3. The degradable biomedical wrought magnesium alloy of claim 1, wherein: the mass of the refining agent is 0.5-1.2% of the total mass of the magnesium alloy.
4. The degradable biomedical wrought magnesium alloy of claim 1, wherein: the stirring conditions are as follows: forward rotation at 100 r/min-200 r/min for 10-15 min, and backward rotation at 100 r/min-200 r/min for 10-15 min.
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