CN109778035B

CN109778035B - Degradable biomedical Mg-Bi-Zn-Ca alloy and preparation method thereof

Info

Publication number: CN109778035B
Application number: CN201910004559.4A
Authority: CN
Inventors: 程伟丽; 刘妍慧; 郝美娟; 成世明; 王红霞; 牛晓峰
Original assignee: Taiyuan University of Technology
Current assignee: Shanxi Regal Metal New Material Co ltd
Priority date: 2019-01-03
Filing date: 2019-01-03
Publication date: 2021-01-15
Anticipated expiration: 2039-01-03
Also published as: CN109778035A

Abstract

A degradable biomedical Mg-Bi-Zn-Ca alloy and a preparation method thereof belong to the technical field of magnesium alloy materials, can solve the defects of over-high corrosion rate, uneven corrosion and the like of the magnesium alloy, and comprises the following components in percentage by weight: mg: 96.4 to 98.8wt.%, Bi: 0.4-1.2 wt.%, Zn: 0.4-1.2 wt.%, Ca: 0.4 to 1.2wt.% in N₂+CO₂Under the protective atmosphere, a resistance furnace is adopted for smelting to obtain a blank, and the blank obtained by casting is directly extruded and deformed after being mechanically processed to obtain an extruded blank. The extruded magnesium alloy has a nano-scale reinforcing phase and a micro-scale fine crystalline structure which are dispersed and distributed, and the average recrystallized grain size is 9.5-10.5 mu m. The Mg-Bi-Zn-Ca alloy has good uniform corrosivity and mechanical property.

Description

Degradable biomedical Mg-Bi-Zn-Ca alloy and preparation method thereof

Technical Field

The invention belongs to the technical field of magnesium alloy materials, and particularly relates to a degradable biomedical Mg-Bi-Zn-Ca alloy and a preparation method thereof.

Background

Stainless steel, cobalt chromium alloy and titanium alloy are widely used bone implant materials at present. However, these materials need to be removed after a second operation, which increases the cost of medical care and patient pain. The magnesium alloy has density and elastic modulus similar to those of human bones, so that the stress shielding effect can be avoided. In addition, the magnesium alloy has degradability and absorbability, so that secondary operation is avoided. However, the degradation rate of the currently developed magnesium alloy is not controllable, so that the magnesium alloy fails before the tissue is healed, thereby influencing the application of the magnesium alloy in the biomedical field.

Disclosure of Invention

The invention provides a degradable biomedical Mg-Bi-Zn-Ca alloy and a preparation method thereof, aiming at the defects of over-high corrosion rate, uneven corrosion and the like of magnesium alloy, and the alloy has good corrosion resistance and mechanical property.

The invention adopts the following technical scheme:

a degradable biomedical Mg-Bi-Zn-Ca alloy comprises the following components in percentage by weight: mg: 96.4 to 98.8wt.%, Bi: 0.4-1.2 wt.%, Zn: 0.4-1.2 wt.%, Ca: 0.4-1.2 wt.% of nano-scale Mg dispersed on the alloy matrix₃Bi₂The reinforcing phase has an average grain size of 9.5 to 10.5 μm.

A preparation method of degradable biomedical Mg-Bi-Zn-Ca alloy comprises the following steps:

step one, preparing a blank: pure magnesium, pure bismuth, pure zinc and Mg-30 percent Ca intermediate alloy with the purity of more than 99.9 percent are put into a graphite crucible according to the proportion and are smelted by a resistance furnace, and CO is adopted in the smelting process₂+N₂Gas shielded liquid surface, CO₂And N₂The volume ratio is 1: 9-16, after all the raw materials are melted, the temperature is kept at 700-750 ℃ for 15-20 minutes, RJ-2 type magnesium alloy refining agent is added into the melted alloy liquid for refining after the temperature is kept, and the addition amount of the magnesium alloy refining agent is 0.8-1.6% of the mass of the melted alloy; standing for 15-30 minutes after refining is finished, pouring the molten liquid into a metal mold at 720-730 ℃ to obtain a cylindrical sample blank, wherein the diameter of the cylindrical sample blank is 45mm, and the metal mold is preheated to 200-220 ℃ before casting;

step two, forward extrusion: directly make extrusion blank through machining to the blank after the casting, extrusion blank's diameter is 35~45mm, and is high for 45~50mm, polishes extrusion blank surface with abrasive paper bright, and the extrusion is ended, obtains the extrusion rod, and the diameter of extrusion rod is 10mm, and the blank keeps warm at 300~320 ℃ for 1h before the extrusion, and extruded technological parameter is: the extrusion temperature is 300-320 ℃, the extrusion rate is 0.1 mm/s, and the extrusion ratio is 16: 1.

The invention has the following beneficial effects:

alloying is a commonly used method for improving the corrosion resistance of magnesium alloy, Bi is a low-cost and non-cytotoxic green element, Zn is one of essential elements existing in human body, the strengthening effect is second to Al, Ca is one of the most extensive mineral elements existing in human body, and the method has important promotion effect on the growth of human skeleton and can promote the dynamic recrystallization process and refine grains of the magnesium alloy.

In addition, under the combined action of three-directional forces in the extrusion process, the coarse second-phase particles can be extruded into fine and dispersedly distributed second-phase particles, dynamic recrystallization is induced, and the corrosion resistance of the alloy is favorably improved.

1. According to the invention, the nontoxic alloy elements Bi, Zn and Ca are added into the magnesium alloy, the addition amount of the nontoxic alloy elements is not more than 1.2%, and the magnesium alloy can be ensured not to harm the health of a human body after being degraded in the human body.

2. The Mg-Bi-Zn-Ca alloy is cast and directly extruded to obtain the nano-scale Mg dispersed and distributed on a matrix₃Bi₂The reinforcing phase improves the comprehensive performance of the alloy. The tensile yield strength is 156-195 MPa, the tensile strength is 245-287 MPa, and the elongation is 22-26%.

3. The Mg-Bi-Zn-Ca alloy of the invention has refined grains after extrusion, and the corrosion resistance and the mechanical property are improved. The corrosion rate in simulated human body fluid is 0.38-0.67 mm/year, and the corroded surface appearance is uniform after the surface corrosion products are washed away.

Drawings

FIG. 1 is a metallographic microstructure of an alloy prepared in example 1 of the present invention.

FIG. 2 is a metallographic microstructure of an alloy prepared in example 2 of the present invention.

FIG. 3 is a metallographic microstructure of an alloy prepared in example 3 of the present invention.

FIG. 4 is a TEM microstructure of an alloy prepared in example 1 of the present invention.

FIG. 5 is a TEM micrograph of an alloy prepared according to example 2 of the present invention.

FIG. 6 is a TEM microstructure of an alloy prepared in example 3 of the present invention.

Detailed Description

The RJ-2 type magnesium alloy refining agent used by the invention comprises the following components in percentage by weight:

example 1

High-purity magnesium ingot (Mg with the purity of 99.99 percent), high-purity bismuth (Bi with the purity of 99.99 percent), high-purity zinc (Zn with the purity of 99.99 percent) and Mg-30 percent Ca intermediate alloy are adopted, and the alloy components are mixed according to the mass fraction of Mg-1Bi-0.8Zn-0.6Ca, namely the mass percentages are respectively: 97.6 percent of Mg, 1.0 percent of Bi, 0.8 percent of Zn and 0.6 percent of Ca (reasonable impurities are not considered in the mass percentage content, and the raw materials with less impurities are selected as much as possible when the raw materials are selected).

Step one, preparing a blank: when smelting, firstly adding a high-purity magnesium ingot into a resistance furnace, and heating under a protective gas environment; when the temperature of the furnace rises to 300 ℃, introducing CO₂And N₂Mixed gas of (2), CO₂And N₂The volume ratio of (A) to (B) is 1: 9; keeping the temperature for 15 minutes when the temperature is increased to 720 ℃; adding bismuth and zinc after the magnesium ingot is melted, heating to 740 ℃, keeping the temperature for 15 minutes, refining at 740 ℃ by using an RJ-2 type magnesium alloy refining agent, wherein the addition amount of the refining agent is 0.8 percent of the mass of the melt, stirring for 5 minutes, standing for 15 minutes, and then casting into a metal mold at 720 ℃; the preheating temperature of the die is 200 ℃, and the refining method is well known to those skilled in the art.

Step two, forward extrusion: and (4) directly carrying out mechanical processing on the blank obtained by casting in the step one to obtain an extruded blank with the diameter of 35mm and the height of 45 mm. And then polishing the surface of the blank by using sand paper to be bright, preserving the heat of the blank for 1h at 300 ℃ before extrusion, wherein the extrusion process parameters are as follows: the extrusion temperature is 300 ℃, the extrusion rate is 0.1 mm/s, the extrusion ratio is 16: 1, and finally, extrusion is finished to obtain an extrusion bar with the diameter of 10 mm.

The alloy prepared by the method has the yield strength of 195MPa at room temperature, the tensile strength of 287MPa and the elongation of 26 percent, the corrosion rate in simulated body fluid is 0.38 mm/year, and the corroded surface appearance is more uniform after surface corrosion products are washed away.

FIG. 1 shows a Mg-1Bi-0.8Zn-0.6Ca alloy prepared in example 1Metallographic microstructure of the material (ED-TD plane). As can be seen from the figure, the dynamic recrystallization grains of the alloy structure are relatively fine, and the average grain size is 10.5 μm. FIG. 4 shows nanoscale Mg₃Bi₂The reinforcing phase is dispersed in the matrix.

Example 2

High-purity magnesium ingot (Mg with the purity of 99.99 percent), high-purity bismuth (Bi with the purity of 99.99 percent), high-purity zinc (Zn with the purity of 99.99 percent) and Mg-30 percent Ca intermediate alloy are adopted, and the alloy components are mixed according to the mass fraction of Mg-1.2Bi-1.2Zn-1.2Ca, namely the mass percentages are respectively as follows: 96.4 percent of Mg, 1.2 percent of Bi, 1.2 percent of Zn and 1.2 percent of Ca (reasonable impurities are not considered in the mass percentage content, and the raw materials with less impurities are selected as much as possible when the raw materials are selected).

Step one, preparing a blank: when smelting, firstly adding a high-purity magnesium ingot into a resistance furnace, and heating under a protective gas environment; when the temperature of the furnace rises to 300 ℃, introducing CO₂And N₂Mixed gas of (2), CO₂And N₂In a volume ratio of 1: 16; keeping the temperature for 15 minutes when the temperature is increased to 720 ℃; adding bismuth and zinc after the magnesium ingot is melted, heating to 740 ℃, preserving heat for 20 minutes, then refining at 740 ℃ by using an RJ-2 type magnesium alloy refining agent, wherein the addition amount of the refining agent is 1.6 percent of the mass of the melt, stirring for 5 minutes, standing for 30 minutes, and then casting into a metal mold at 730 ℃; the mold preheating temperature is 220 ℃ and the refining method is well known to those skilled in the art.

Step two, forward extrusion: and (4) directly machining the blank obtained by casting in the step one to obtain an extruded blank with the diameter of 45mm and the height of 50 mm. And then polishing the surface of the blank by using sand paper to be bright, preserving the heat of the blank for 1h at 320 ℃ before extrusion, wherein the extrusion process parameters are as follows: the extrusion temperature is 320 ℃, the extrusion rate is 0.1 mm/s, the extrusion ratio is 16: 1, and finally, extrusion is finished to obtain an extrusion bar with the diameter of 10 mm.

The alloy prepared by the method has the yield strength of 156MPa at room temperature, the tensile strength of 245MPa, the elongation of 22 percent, the corrosion rate of 0.67 mm/year in simulated body fluid, and the corroded surface appearance is more uniform after the surface corrosion products are washed away.

FIG. 2 is a metallographic microstructure (ED-TD plane) of a Mg-1.2Bi-1.2Zn-1.2Ca alloy material prepared in example 2. As can be seen from the figure, the dynamic recrystallization grains of the alloy structure are relatively fine, and the average grain size is 9.5 μm. FIG. 5 also shows the dispersed Mg distribution₃Bi₂And (4) a reinforcing phase.

Example 3

High-purity magnesium ingot (Mg with the purity of 99.99 percent), high-purity bismuth (Bi with the purity of 99.99 percent), high-purity zinc (Zn with the purity of 99.99 percent) and Mg-30 percent Ca intermediate alloy are adopted, and the alloy components are mixed according to the mass fraction of Mg-0.8Bi-0.6Zn-0.6Ca, namely the mass percentages are respectively as follows: 98.0 percent of Mg, 0.8 percent of Bi, 0.6 percent of Zn and 0.6 percent of Ca (reasonable impurities are not considered in the mass percentage content, and the raw materials with less impurities are selected as much as possible when the raw materials are selected).

Step one, preparing a blank: when smelting, firstly adding a high-purity magnesium ingot into a resistance furnace, and heating under a protective gas environment; when the temperature of the furnace rises to 300 ℃, introducing CO₂And N₂Mixed gas of (2), CO₂And N₂The volume ratio of (A) to (B) is 1: 12; keeping the temperature for 15 minutes when the temperature is increased to 720 ℃; adding bismuth and zinc after the magnesium ingot is melted, heating to 740 ℃, keeping the temperature for 18 minutes, refining at 740 ℃ by using an RJ-2 type magnesium alloy refining agent, wherein the addition amount of the refining agent is 1.2 percent of the mass of the melt, stirring for 5 minutes, standing for 20 minutes, and then casting into a metal mold at 725 ℃; the mold preheating temperature is 210 ℃ and the refining method is well known to those skilled in the art.

Step two, forward extrusion: and (4) directly machining the blank obtained in the first step to obtain an extruded blank with the diameter of 38mm and the height of 48 mm. And then polishing the surface of the blank by using sand paper to be bright, preserving the heat of the blank for 1h at 310 ℃ before extrusion, wherein the extrusion process parameters are as follows: the extrusion temperature is 320 ℃, the extrusion rate is 0.1 mm/s, the extrusion ratio is 16: 1, and finally, extrusion is finished to obtain an extrusion bar with the diameter of 10 mm.

The alloy prepared by the method has the yield strength of 182MPa at room temperature, the tensile strength of 267MPa, the elongation of 24 percent and the corrosion rate of 0.53 mm/a in simulated body fluid, and the corroded surface appearance is more uniform after the surface corrosion products are washed away.

FIG. 3 is a metallographic microstructure (ED-TD plane) of a Mg-0.8Bi-0.6Zn-0.6Ca alloy material prepared in example 3. As can be seen from the figure, the dynamic recrystallization grains of the alloy structure are relatively fine, and the average grain size is 9.9 μm. FIG. 6 also shows the dispersed Mg distribution₃Bi₂And (4) a reinforcing phase.

Claims

1. A degradable biomedical Mg-Bi-Zn-Ca alloy is characterized in that: the paint consists of the following components in percentage by weight: mg: 96.4 to 98.8wt.%, Bi: 0.4-1.2 wt.%, Zn: 0.6-1.2 wt.%, Ca: 0.6-1.2 wt.%, the sum of the components is 100%, and the alloy has nano-scale Mg dispersed on an alloy matrix₃Bi₂The reinforcing phase has an average grain size of 9.5 to 10.5 μm.

2. The method for preparing the degradable biomedical Mg-Bi-Zn-Ca alloy according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:

step one, preparing a blank: pure magnesium, pure bismuth, pure zinc and Mg-30 percent Ca intermediate alloy with the purity of more than 99.9 percent are put into a graphite crucible according to the proportion and are smelted by a resistance furnace, and CO is adopted in the smelting process₂+N₂Gas shielded liquid surface, CO₂And N₂The volume ratio is 1: 9-16, and the temperature is kept for 15 minutes when the temperature is raised to 720 ℃; adding bismuth and zinc after a magnesium ingot is melted, preserving heat at 740 ℃ for 15 minutes after all raw materials are melted, adding an RJ-2 type magnesium alloy refining agent into a melted alloy liquid for refining after heat preservation, wherein the addition amount of the magnesium alloy refining agent is 0.8-1.6% of the mass of the melted alloy; standing for 15-30 minutes after refining is finished, pouring the molten liquid into a metal mold at 720-730 ℃ to obtain a cylindrical sample blank, wherein the diameter of the cylindrical sample blank is 45mm, and the metal mold is preheated to 200-220 ℃ before casting;