Materials modeling and simulation of isothermal forging of rolled AZ31B magnesium alloy: Anisotropy of flow

Isothermal forging of a rib-web shape in AZ31B magnesium alloy in the rolling direction was conducted at speeds of 0.01-10mms^-1 in the temperature range of 300-500°C with the purpose of validating the results of materials models involving kinetic analysis and processing map. The process was also simulated using finite element method DEFORM to obtain the local values of strain and strain rate. Forging parallel to the rolling direction in the range 375-550°C and 0.0003-0.3s^-1 under the conditions of dynamic recrystallization (DRX) resulted in a symmetrical cup-shape while at other conditions an elliptical boat-shape was produced with the major axis coinciding with the transverse direction and the minor axis aligned with the normal direction. This anisotropy of flow has been attributed to the strong basal texture in the rolled plate and the dominance of prismatic slip at lower temperatures. In the DRX domain on the other hand, pyramidal slip dominates along with cross-slip as the recovery mechanism, which destroys the initial texture and restores the symmetry of flow. The grain size variation for forgings done in the DRX domain validated the predictions of the material models. © 2011 Elsevier Ltd.