Study On Composition Design And Performance Of The Novel Biodegradable Zinc Alloy

Zn and its alloys have been considered as the most potential and biodegradable materials in the 21 st century.These have attracted a lot of attentions of many national and international scholars because of their versatility as biological compatibility and suitable corrosion resistance.Being biodegradable materials,they have a drawback of having poor mechanical properties,so it was the need of the hour to overcome this problem.In this study,binary(Zn-Mg)and ternary(Zn-Mg-Ca)alloys were developed and the extrusion processing was applied to improve the mechanical properties.A comprehensive study was carried out to investigate the properties of the alloys using metallographic,micro-hardness,tensile,electrochemical,immersion and bio-compatibility tests.We also paid attentions to check the effect of the alloys' contents on strength mechanism and corrosion behavior in simulated body fluid(PBS).The results indicated that the binary alloys(Zn-Mg)can easily crystallize in the form of an unbalanced microstructure.It was noted that when Mg contents were lower than 2wt.%,the phases of Zn-Mg alloys were composed of ?-Zn and eutectic groups of ?-Zn and Mg2Zn11,and when the Mg contents were greater than 2wt.%,the alloy was mainly composed of ?-Zn and peritectic groups of ?-Zn and MgZn2,but when the content of Mg was exactly 2wt.%,the alloy was consisted by ?-Zn phase,part of the peritectic tissue and pseudo eutectic structure of ?-Zn and MgZn2.The hardness of the Zn-Mg alloy increased with the increasing of Mg contents.The electrochemical test results showed that ZnMg2 the best electrochemical corrosion resistance behavior.Study on structure of ternary alloys(Zn-Mg-Ca)showed that the cast alloys had serious segregation,but segregation can be eliminated after extrusion deformation.The electrochemical test results showed that the electrochemical properties of cast alloy was deeply affected by segregation.However,effects of the concentrations of alloy elements on electrochemical performance were not obvious.Keeping the Mg contents very low,then the corrosion resistance can be improved by the increasing Ca contents in the alloy,but if the Mg contents were high then effect of Ca contents was not considerable.The extruded alloy's corrosion resistance was better than the cast one.Experimental results showed that with the increase of Mg contents,the tensile strength rised and the maximum tensile strength of Zn-Mg-Ca alloy was attained a maximum of 440.5MPa,169.5MPa of the highest yield strength,and 6.08% of the best elongation.The immersion test of Zn-Mg-Ca alloys exhibited that Ca can effectively reduce the alloy's degradation rate.The bio-compatibility results showed that Zn alloy have no toxicity to mouse-derived L-929 fibroblast cells,and the low concentration of alloy ions could promote the growth of mouse fibroblast cells.