Microstructure, mechanical properties, and corrosion behavior of a biodegradable Zn–1.7Mg–1Ca alloy processed by KoBo extrusion

The present study investigated the effects of Mg and Ca additions to pure Zn on its microstructure, mechanical properties, and corrosion resistance, as well as the influence of severe plastic deformation via KoBo extrusion on these properties for both pure Zn and the ternary Zn–1.7Mg–1Ca (wt.%) alloy. The microstructural analysis conducted using scanning electron microscopy and electron backscatter diffraction revealed that the addition of alloying elements led to the formation of Mg2Zn11 and CaZn13 intermetallic compounds. The equivalent strain generated via KoBo extrusion was calculated using FORGE® NxT software. The mechanical testing results revealed that the ternary Zn alloy had 186% higher hardness (100 ± 2.6 HV), 210% higher YS (31 ± 3.5 MPa), and 254% higher UTS (85 ± 7.4 MPa) compared to pure Zn. Moreover, the application of KoBo extrusion was found to be beneficial for further enhancing the mechanical properties of both pure Zn and the ternary Zn alloy. Furthermore, the results of the potentiodynamic polarization test performed in Ringer's solution for evaluating the corrosion resistance of the fabricated alloys revealed that the addition of alloying elements increased the corrosion rate by 11% compared to pure Zn (from 145 ± 9 to 161 ± 8 μm/year) due to the micro-galvanic cell formation between different phases, and the KoBo extrusion process increased the corrosion rate of pure Zn but decreased the corrosion rate of the ternary Zn alloy.