On crystal plasticity formability analysis for magnesium alloy sheets

Sheet metal formability is assessed in terms of the Forming Limit Diagram (FLD) for magnesium alloys with Hexagonal Close Packed (HCP) crystallographic structure. All simulations are based on the recently developed elastic–visco-plastic self-consistent (EVPSC) model and the classical Taylor model, in conjunction with the M–K approach. The role of crystal plasticity models and the effects of basal texture on formability of magnesium alloy AZ31B sheet are studied numerically. It is observed that formability in HCP polycrystalline materials is very sensitive to the intensity of the basal texture. The path-dependency of formability is examined based on different non-proportional loading histories, which are combinations of two linear strain paths. It is found that while the FLD in strain space is very sensitive to strain path changes, the Forming Limit Stress Diagram (FLSD) in stress space is much less path-dependent. It is suggested that the FLSD is much more favourable than the FLD in representing forming limits in the numerical simulation of sheet metal forming processes. The numerical results are found to be in good qualitative agreement with experimental observations.