Combined effects of grain size refinement and dynamic precipitation on mechanical properties of a new magnesium alloy

Abstract

Two well-known methods for enhancing the strength and controlling the anisotropy in magnesium alloys are precipitation hardening and grain size refinement. In this study, both methods are combined in an attempt to achieve optimal strengthening and anisotropy control: this was done via severe plastic deformation using Equal Channel Angular Processing (ECAP) of a precipitation hardenable magnesium alloy, Mg–6Zn–0.6Zr–0.4Ag–0.2Ca (wt%), within the temperature range of 125–200 °C. ECAP specimens were processed along different routes, where mechanically several of the ECAP samples show ultra-high strength levels approaching 400 MPa. The roles of grain size, texture, and precipitate morphology on mechanical properties are systematically investigated. It is shown here that the resulting microstructures generally show a refined grain size around 500 nm with a complex distribution of Mg-Zn enriched precipitates, which via ECAP either dynamically precipitate or are redistributed from the starting condition.