| Due to its good biocompatibility,excellent degradability,abundant resources,low price and other advantages,magnesium alloy has gradually entered the eyes of material scientists and medical experts in recent years.However,due to the reaction between magnesium and its alloy in human body and human blood,the corrosion rate of metal materials is difficult to control,the alloy is difficult to play a supporting role in the body,and the treatment is difficult to achieve the expected effect,which hinders the application and promotion of magnesium alloy materials in the field of biological implant materials to a certain trend.Therefore,how to improve the corrosion resistance and mechanical properties of magnesium alloys in the physiological environment is very important.In this paper,Mg-2Zn-1.5Sn alloy was used as the base alloy,and Zr was added to optimize the alloy composition.The effects of Zr content on the microstructure and properties of as-cast Mg-2Zn-1.5Sn-x Zr alloy were studied.Then,the Mg-2Zn-1.5Sn-0.6Zr alloy with excellent properties was heat treated,and the influence of different heat treatment processes on the microstructure and properties of the alloy was studied to determine the appropriate heat treatment process.Finally,the heat-treated Mg-2Zn-1.5Sn-0.6Zr alloy was rolled,and the effect of rolling deformation rate on the microstructure and properties of the alloy was studied.OM,SEM,XRD and other equipment were used to analyze the microstructure of different states of the alloy.The mechanical properties of the alloy were studied by room temperature tensile test and hardness test.At the same time,the corrosion resistance of the alloy was studied by hydrogen evolution experiment and electrochemical test.With the increase of Zr content,the as-cast Mg-2Zn-1.5Sn-x Zr alloy changes from the typical dendrite structure to a more regular equiaxed crystal structure.When Zr content is 0.6 wt%,the maximum tensile strength of the alloy is 171.0 MPa.However,the addition of Zr has an adverse effect on the plasticity of the alloy.When the content of Zr increases to 0.6 wt%,the elongation decreases from 14.0 % to 11.8 %.The minimum corrosion rate of as-cast Mg-2Zn-1.5Sn-0.6Zr alloy is 1.25 mm/year in hydrogen evolution experiment,which is 30.2 % lower than that of the alloy without Zr content,indicating that the corrosion resistance of the magnesium alloy with Zr element added has been significantly improved.When the heat treatment process is 500 ℃/18 h,the hardness,tensile strength and elongation of Mg-2Zn-1.5Sn-0.6Zr alloy increase by 16.7 %,17.7 % and 36 %compared with the alloy without heat treatment.At this time,the corrosion resistance of the alloy is the best,and the corrosion rate is 0.88 mm/year.The grain size of Mg-2Zn-1.5Sn-0.6Zr alloy decreases with the increase of deformation rate after rolling.When the rolling deformation rate is 60 %,the tensile strength of the alloy is 240.0MPa,which increases by 19 % and 40 % compared with the heat treatment state and the cast state.At this time,the elongation of the alloy is 12 %,and the mechanical properties of the alloy meet the performance index of biomaterial implantation in human body,and the elongation is better than that of the same industry of biomedical alloys.When the deformation rate is 60 %,the corrosion potential of the alloy is positive at-1.405 V,the corrosion rate is low at 0.63 mm/year,and the corrosion rate decreases by 20.3 %.In this case,the corrosion rate of the alloy meets the performance index of biomaterial implantation in human body.The toxicity level of the rolled Mg-2Zn-1.5Sn-0.6Zr alloy extract is 0-1,indicating that the rolled Mg-2Zn-1.5Sn-0.6Zr alloy is non-toxic and can be used as biological implant materials. |
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