A model for deformation twinning in Tantalum under shock coupled with crystal plasticity

A finite strain phase field model for phase changes is derived to investigate the competition between <112> twinning and plastic activity during the rapid compression of Tantalum. The description of phase transformations relies on the Phase Field - Reaction Pathways formalism [1]. Transformation paths up to any target level are generated so that phenomena such as retwinning are reproduced. A crystal plasticity model is further embedded at each variant. The model is polyphase in the sense that the individual plastic behaviour of each transformation variant is taken into account. To reach finer scales in the description of the mechanical behavior, the chosen crystal plasticity model uses dislocation densities as internal variables. The proposed coupling between plasticity and phase transition takes into account two levels of inheritance: global inheritance through the weighting of the plastic contributions of all variants, and local inheritance through an ad hoc dislocation inheritance model. Simulations are performed using a 3D total Lagrangian code with an element-free Galerkin least-squares formulation. Computations results evidence strong correlations between microstructural evolutions and the local repartition of defects.

[1] Denoual and Vattré, JMPS, pp. 91-107, 2016.