Optimisation of alloy composition for highly-formable magnesium sheet

The effectiveness of Ca or Gd addition on ductility and formability of Mg–Zn–Zr based dilute alloys in deep drawing has not been systematically compared previously. In this study, formable Mg–Zn–Gd–Zr and Mg–Zn–Ca–Zr sheet alloys are produced by hot rolling. These sheets have similarly weakened basal texture, but the sheet of the Mg–Zn–Gd–Zr alloys has higher ductility and formability than that of Mg–Zn–Ca–Zr alloys. The combined addition of 0.2wt% Ca and 0.4wt% Gd to the Mg–1Zn–0.5Zr（wt%） alloy leads to a Mg–1Zn–0.4Gd–0.2Ca–0.5Zr alloy that has even better ductility, and its formability during deep drawing is comparable to the benchmark Al6016 sheet. An increase in Ca content from 0.2wt% to 0.5wt% leads to decreased sheet ductility and formability, predominantly due to grain boundary embrittlement.