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 FeZn_10.98 modification (FeZn₁₃ → FeZn_10.98), 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.