Microstructure and tensile properties of Mg-3Al-1Zn sheets produced by hot roller-cold-material rolling

Mg-3Al-1Zn (AZ31) alloy sheets with various thickness reductions from 10% to 60% were fabricated in a single pass at 150 degrees C by hot-roller-cold-material rolling. The rolled sheets were then evaluated by microstructural characterization and tensile testing. The strength shows an increase with increasing thickness reduction from 10% to 40%, but the further increase in thickness reduction leads to a decrease in strength. Yield strengths of 273 MPa along the rolling direction and 357 MPa along the transverse direction are obtained for the sheet with 40% thickness reduction, which is characterized by highly elongated grains and high density dislocations, together with a few ultrafine, recrystallized grains in microstructure. The variation in strength with thickness reduction is discussed in light of the strengthening contributions from grain size and dislocation density.