Effect of Magnesium Content on Microstructure and Electrochemical Properties of Zn-xMg Alloy

Zinc alloy has good biocompatibility and controlled degradation rate，which is expected to be a new type of biodegradable bioimplantable metal material.The effect of Mg content on microstructure evolution， microhardness， hydrogen precipitation and corrosion resistance of Zn-xMg alloys (x ＝1.0， 2.0， 5.0， 7.5， 10.0， mass fraction， %) was investigated by using metallurgical microscope， X-ray diffractometer，electron scanning electron microscope， Vickers hardness tester and electrochemical workstation.Results showed that with the increase of Mg content， the grain size decreased gradually， and several new diffraction peaks appeared in the X-ray diffraction spectrum， giving rise to a new phase Mg2Zn11 in the alloy.MgZn2 compounds appeared when the Mg content reached 5.0%， at which time the grains were transformed from equiaxed to dendritic with intersecting orientations， and the dendritic crystals were gradually coarsened with the increase of Mg content.Meanwhile， the hardness of Zn-xMg alloys showed an increasing and then decreasing trend with increasing Mg content， and the hardness of Zn-7.5Mg alloy reaches the maximum value (120 HV5).The results of electrochemical tests in Hank’s solution medium exhibited that the Zn-7.5Mg alloy had better corrosion resistance and the best hydrogen precipitation performance.