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.