Microstructural and Mechanical Properties of a Heat-Treated EV31A Magnesium Alloy Fabricated Using the Stir-Casting Process

Abstract

This study aims to prepare a stir-cast EV31A magnesium alloy and investigate the effects of the T4 condition (solid solution strengthening) and T6 condition (solid solution strengthening cum age hardening) on the phases, microstructure, mechanical properties, and fractography. The solid solution at 520 °C for 8 h allows the Rare-Earth Elements (REE) to dissolve in the Mg matrix, but the solubility is limited by the presence of Zn. This phenomenon is responsible for the T4 heat-treated alloy’s strengthening, which raises the UTS to 212 MPa. The formation of new grains within the grains causes an increase in grain boundaries and dislocations during the T6 heat treatment process, increasing the strength (UTS) of the EV31A alloy to 230 MPa. In all three test conditions, the fractography of tensile samples revealed a cleavage-ductile/mixed mode fracture. As expected, the fine-grained T6 sample exhibited superior strengthening at the expense of ductility.

Keywords

• stir casting
• magnesium alloy
• EV31A
• mechanical properties
• heat treatment