Effects of Zn Additions on the Room Temperature Formability and Strength in Mg–1.2Al–0.5Ca–0.4Mn Alloy Sheets

Abstract

We investigated the effects of Zn additions on the mechanical properties and microstructure of Mg–1.2Al–0.5Ca–0.4Mn and Mg–1.2Al–0.5Ca–0.4Mn–1.6Zn (wt%) alloy sheets fabricated by twin-roll casting and conventional hot rolling. The room temperature stretch formability of the solution-treated alloy sheet is improved by the addition of Zn. The Mg–1.2Al–0.5Ca–0.4Mn–1.6Zn alloy shows an excellent stretch formability with the larger Index Erichsen value of 8.2 mm due to a weak transverse direction split texture. The development of the weak texture is attributed to the uniform grain growth by the solute segregation to the recrystallized grain boundaries. Subsequent bake-hardening treatment, 2% pre-strain at 170 °C for 20 min leads to substantial increase in strength without the loss of ductility. The bake-hardened Mg–1.2Al–0.5Ca–0.4Mn–1.6Zn alloy exhibits a high tensile yield strength of 235 MPa with an elongation to failure of 27.1%.