SMIG model: A new geometrical model to quantify grain boundary-based plasticity

Abstract Stress-assisted grain boundary migration is a mechanism that has proven active in polycrystals but that relies on a limited number of models. Those models do not apply to general grain boundaries and often fail to reproduce the intensity of the coupling between the migration distance and the produced shear strain. Recently a new geometrical model, entitled the shear migration geometrical (SMIG) model, that is valid for all tilt boundaries has been introduced to account for the low coupling factors observed experimentally. In the present work we propose, on the basis of this model, (i) to determine, for a given tilt grain boundary, the number of possible coupling modes and (ii) to evaluate the shuffling needed to rearrange atoms as the grain boundary migrates. We will show that, for a given grain boundary defined by a misorientation angle and a grain boundary plane, it is almost always possible to find a coupling mode implying the shuffling of up to 20 atoms, supposedly without long-range diffusion. This characteristic is of prime importance in polycrystals where collective grain boundary motions are required to accommodate strain.