Effect of Ca addition on the microstructure, mechanical properties and corrosion rate of degradable Zn-1Mg alloys

Abstract

The microstructural evolution, mechanical properties and degradation behaviors of as-cast Zn-1Mg alloy and Zn-1Mg-xCa (x = 0.3 wt% and 0.5 wt%) alloys were investigated. The microstructural evolution showed that adding Ca element effectively refined α-Zn from coarse dendrites to equiaxed grains, and the average size gradually decreased with the increasing contents of Ca in Zn-1Mg alloy. Moreover, the morphology of eutectic Mg2Zn11 phases changed from lamellar shape to honeycomb, and the amount of precipitated CaZn13 phases distributed in grain boundaries increased, when the 0.3 wt% and 0.5 wt.%Ca were introduced into Zn-1Mg alloy melt. Tensile test results revealed that the yield strength (YS), ultimate tensile strength (UTS) and elongation (El) of Zn-1Mg-0.5Ca alloy (118.7 MPa, 169.3 MPa, 3.42% for YS, UTS and El, respectively) is improved by 40.5%, 41.4% and 189.8%, respectively, compared with Zn-1Mg alloy (84.5 MPa, 119.7 MPa, 1.18% for YS, UTS and El, respectively). The method of electrochemical polarization testing was employed to measure the corrosion rate of Zn-1Mg-xCa alloys in Hanks simulated body fluid. The result exhibited that the corrosion rate of Zn-1Mg alloy without and with 0.3 wt% and 0.5 wt%Ca addition gradually increased, which was 0.125 mm.a−1, 0.176 mm.a−1 and 0.190 mm.a−1, respectively. In addition, the corrosion rates of Zn-1Mg-xCa alloys immersed in Hank’s solution holding for one month were summarized as: as-cast Zn-1Mg-0.5Ca alloy (0.182 mm.a−1)> as-cast Zn-1Mg-0.3Ca alloy (0.168 mm.a−1)> as-cast Zn-1Mg alloy (0.134 mm.a−1). The investigation of mechanical properties and corrosion rate demonstrated that newly developed Zn-1Mg alloys with Ca addition can be thought of a hopeful biodegradable medical material.