Effect of temperature, strain rate and fibre orientation on the plastic flow behaviour and formability of AZ31 magnesium alloy

The sheet formability of AZ31 magnesium alloy has been widely investigated by means of uniaxial tensile and hemispherical punch tests, performed at different temperatures and strain rates, using samples with different fibre orientations. The results of the uniaxial tensile tests were analysed in terms of flow curves, ductility and microstructural evolution. They show that the flow stress decreases and ductility increases as temperature rises and strain rate reduces; the ductility is almost independent of the fibre orientation that, however, slightly affects the flow stress values. The formability, described by the forming limit curves (FLCs), improves with increasing temperature and decreasing strain rate. Moreover, formability along the rolling direction (RD) is higher than that along the transversal one (TD), even if the FLCs obtained along the TD have a larger extension in the drawing side than the ones along the RD. Such behaviours were related to the constitutive parameters and microstructure developed during deformation.