Effects of minor Ca addition on microstructure and mechanical properties of the Mg-4.5Zn-4.5Sn-2Al-based alloy system

► Effects of minor Ca on the Mg-Zn-Sn-Al alloy were firstly studied. ► The as-cast alloy with 0.2% Ca exhibits best mechanical properties. ► The as-rolled alloy with 0.2% Ca exhibits UTS, YTS and Er of 406 MPa, 285 MPa and 6.6% respectively. ► 0.2% Ca addition refines twins and DRX grains.