The main strengthening phases transformation and their strengthening mechanisms in as-cast Mg-Gd-(Y)-Zn alloys: A review

Magnesium alloys are highly sought after as environment-friendly engineering materials for the 21st century. Mg-RE (rare earth) alloys, especially Mg-Gd-(Y)-Zn alloys, have attracted significant interest in the past two decades due to their potential high performances over conventional or commercial magnesium alloys. Recent research has revealed that the LPSO、 β series and γ series phases are the main strengthening phases in Mg-Gd-(Y)-Zn alloys. This article aims to provide a review of recent progress on the transformation of these main strengthening phases in the as-cast Mg-Gd-(Y)-Zn alloys, especially the co-existence of multiple strengthening mechanisms. Further, substantial research recommendations for the future development of high-performance and even ultra-high-strength casting Mg-RE alloys are proposed in terms of casting procedure, heat treatment process, alloying elements, and strength-plasticity trade-off.