The influence of the as-hot rolled microstructure on the elevated temperature mechanical properties of magnesium AZ31 sheet

An AZ31 alloy was rolled at temperatures between 350 and 450 °C, after soaking at rolling temperature for either 1 or 10 h, using various rolling reductions per pass and rolling speeds. Two extremes of as-hot rolled microstructure were generated: (i) a banded structure comprised of very fine equiaxed grains, but with a few ‘pancaked grains’, i.e. ‘partially recrystallized’, and (ii) much coarser equiaxed grains with no banding or pancaked grains, i.e. ‘recrystallized’. These hot-rolled sheets were tensile tested at temperatures between 300 and 450 °C, with strain rates from 0.1 to 0.001 s−1. Grain boundary sliding appeared to dominate at higher test temperatures and lower strain rates, and dynamic recrystallization dominated at lower temperatures and higher strain rates. In terms of good high temperature formability (i.e. low flow stress and high ductility) the partially recrystallized structure was more beneficial than the fully recrystallized structure, under test conditions where grain boundary sliding dominated.