Deformation behavior of as-rolled and strip-cast AZ31 magnesium alloy sheets

Deformation behavior of AZ31 Mg alloy has been studied in relation to test temperature and grain size. Tensile specimens were prepared in the rolling direction of an as-rolled as well as a strip-cast sheet with 1 mm thickness. The as-rolled and strip-cast sheets had the mean grain sizes of 75 μm and 5 μm, respectively. Tensile tests were then carried out under the strain rate of 10−2/s at room temperature, 100 °C, and 200 °C. Biaxial tests were also performed to obtain flow curves in terms of stress and strain as well as to estimate the biaxial forming limit. Plastic deformation was found due to the usual dislocation slip and dynamic recrystallization (DRX) together with some twinning. A number of twins were observed especially in large grained specimens at low homologous temperatures. The strip-cast sheet exhibited many small grains generated by the DRX at higher temperature. These fine grains due to DRX appeared to lead into an enhanced formability, evidenced by a sudden formability increase of a strip-cast sheet at 200 °C. The double twin mode was observed under biaxial loading, contrary to extension twins observed under uniaxial loading.