A full-field approach to simulate microstructure evolution during high-temperature deformation of polycrystalline aggregates including dislocation (glide and climb) and diffusion creep mechanisms.

The VPFFT-ELLE numerical scheme is a micro-dynamic approach able to simulate the microstructure evolution of polycrystalline and polyphase aggregates during deformation and recrystallisation (www.elle.ws). The approach has been widely used to simulate the dynamic recrystallisation of ice, halite and olivine aggregates, among others. A limitation of this numerical scheme is that is limited to viscoplastic deformation by dislocation glide. However, at homologous high temperatures and low stresses, point-defect mediated mechanisms such as dislocation climb and diffusion creep are important in order to accommodate plastic deformation in polycrystalline aggregates.

We present an update of the approach by incorporating a new scheme able to simulate dislocation climb and diffusion creep in an elasto-viscoplastic regime. The approach is based on a previously small-strain version of a formulation based on the fast Fourier transforms (FFT) for the prediction of micromechanical fields in polycrystals (Lebensohn et al., 2012). The new approach integrates a rate-sensitivity, crystallographically-based constitutive model of a single crystal deforming by climb and glide, combined with an isotropic, linear model for the parametric simulation of active diffusion within grains and at grain boundaries.  

An overview of the theoretical basis of the approach is presented with some benchmarks and applications to the prediction of the effective behaviour and evolution of crystallographic-preferred orientation of highly anisotropic minerals. As expected, the incorporation of both new mechanisms produces a relaxation of differential stresses and the integration of additional scale lengths in the models. However, challenging features are remaining, such as an efficient integration with the recrystallisation processes (grain boundary migration and nucleation of new grains), or appropriate incorporation of transient creep processes.

 

Lebensohn et al (2012) An elasto-viscoplastic formulation based on fast Fourier transforms for the prediction of micromechanical fields in polycrystalline materials, International Journal of Plasticity, 32–33, 59–69.