Using Solution Heat Treatment and Multi Directional Forging to Improve the Mechanical and Corrosion Properties of an Mg–2Zn–0.2Ag Alloy

This study investigated the effects of solution heat treatment and multi-directional forging (MDF) on the microstructure, mechanical, and corrosion properties of an Mg–2Zn–0.2Ag alloy. Microstructural characterization by field emission scanning electron microscopy indicated that the as-cast material consists of some MgZn 2 and Ag-rich MgZn precipitates. These silver-rich MgZn precipitates were entirely and partially dissolved after the solution treatment and MDF, respectively. In addition, the grain size of the as-cast alloy increased by 86% and decreased by 43% after solution heat treatment and MDF, respectively. The ultimate shear strength of the as-cast material increased by 25% and reached 149.5 MPa after MDF processing, while it did not change significantly after solution treatment. The obtained results indicated that the corrosion layer formed on the samples consists of an inner layer (magnesium hydroxide) and an outer layer (phosphate compounds). Based on the corrosion tests, it was found that solution heat treatment and MDF could significantly improve the corrosion resistance of the as-cast Mg–2Zn–0.2Ag. The corrosion resistance ( R p ) obtained from the electrochemical impedance spectroscopy (EIS) test exhibited enhancements of 119% and 152% after heat treatment and MDF processes, respectively. This improvement in corrosion resistance was attributed to the higher stability of the outer layer in both solution-treated and MDF-processed samples, compared to the as-cast material. The results of cell studies also indicated a significant improvement in the cell viability of the solution-treated Mg–2Zn–0.2Ag alloy sample compared with pure Mg. Graphical Abstract