Simulating Discrete Twin Evolution in Magnesium Using a Novel Crystal Plasticity Finite Element Model

An advanced, image-based crystal plasticity FE model is developed for predicting discrete twin formation and associated heterogeneous deformation in the single and polycrystalline microstructure of Magnesium. Twin formation is sensitive to the underlying microstructure and is responsible for the premature failure of Mg. The physics of nucleation, propagation, and growth of deformation-twins are considered in the CPFE formulation. The twin nucleation model is based on dissociation of sessile dislocations into stable twin loops, while propagation is assumed by layer-by-layer atoms shearing on twin planes and shuffling to reduce the energy barrier. A non-local FE-based computational framework is developed to implement the twin nucleation and propagation laws, which governs the explicit formation of each individual twin. The simulation matches satisfactorily with the experiments in the stress-strain-response and predicts heterogeneous twin formation with strain localization.