Factors influencing tensile ductility of ultrafine-grained Mg–3Al–1Zn alloy sheet at elevated temperatures

Tensile elongation behavior of ultrafine-grained (UFG) Mg–3Al–1Zn (AZ31) alloy sheet (with a mean grain size of 1 μm) produced by high-ratio differential speed rolling was studied at elevated temperatures, and factors influencing the ductility were evaluated. The UFG AZ31 showed an obvious advantage in ductility enhancement below 473 K, but the maximum forming temperature was limited due to high thermal instability of the UFG AZ31 microstructure. There was a pronounced effect of grain coarsening during the sample heating and deformation on strain-rate sensitivity and strain hardening. The tensile elongation behavior of UFG AZ31 with high density of thermally stable (Al, Mg)2Ca particles was compared with that of UFG AZ31 to see what happens if grain coarsening is well suppressed in UFG AZ31 alloy.