The polycrystalline plasticity due to slip and twinning during magnesium alloy forming.

In order to simulate the magnesium alloy-forming processes accurately, it is necessary to consider the plastic anisotropy. In this paper, a new rate-independent constitutive model for polycrystalline plastic deformation by slip and twinning has been formulated, and then introduced into a FEM program. Metal flow is assumed to occur by crystallographic slip on given slip and twinning systems within each crystal. Each integration point represents a single crystal. Then uniaxial compression and cup drawing of Mg alloy are studied by using a rate-independent polycrystalline plasticity finite element analysis. In this paper, the ear distributions of the polycrystal are predicted for different typical initial orientation cases. The values of the twinning factors associated with slip system deformation are deduced. It is found that the twinning factors vary with the value of the stress. The basal slip and twinning system plays the dominant role in the deformation of magnesium alloy, which might be the most important contribution to strain hardening. [ABSTRACT FROM AUTHOR]