Corrosion Resistance and Biocompatibility of Ultrafine-Grained Zn–1% Li–2% Mg and Zn–1.0% Mg–1.0% Fe Alloys Obtained by Severe Plastic Deformation

The corrosion resistance and biocompatibility of ultrafine-grained (UFG) Zn–1% Li–2% Mg and Zn–1% Mg–1% Fe zinc alloys, which exhibit unique mechanical properties as a result of severe plastic deformation (SPD) processing, were investigated. The corrosion rate in the UFG Zn–1% Li–2% Mg alloy was found to be 0.0891 mm/year, and this rate in the UFG Zn–1% Mg–1% Fe alloy was found to be 0.061 mm/year. The conducted comparative tests with their coarse-grained (CG) analogs have shown that corrosion processes most intensely occur at the periphery of UFG samples, which are characterized by a greater degree of accumulated deformation, strong refinement of structural elements, intense phase transitions, and completeness of dynamic aging. The increase in the corrosion rate in UFG Zn–1% Li–2% Mg alloy in comparison with its CG analog is explained by the presence of the Mg2Zn11 phase of high content, increased weight fraction of the Zn phase alloyed with Li and Mg atoms, precipitation of Mg2Zn11 particles in it, and decrease in the ~LiZn3 fraction. The growth of the corrosion rate in the UFG Zn–1% Mg–1% Fe alloy is also explained by the increase in the Zn doped phase and precipitation of precipitates in the Zn and Mg2Zn11 phases. In addition, the phase transition of FeZn13 into its FeZn10.98 modification (FeZn13 → FeZn10.98), which is uncharacteristic for the CG state, was found in the near-surface layers of the UFG sample when aged in Ringer’s solution. The results of Alamar Blue metabolic test demonstrated biocompatibility of MG-63 cells for 1 day (more than 50%) and proliferative capacity for 7 days (more than 30%) when incubated with 12.5% extracts of UFG Zn–1% Mg–1% Fe and Zn–1% Li–2% Mg alloy samples. The causes of MG-63 cell death when the content of extracts of zinc alloy samples was increased were analyzed.