Morphological Instability of Grain Boundary under Lateral Applied Strain*

The morphological instability of symmetrical high-angle tilt grain boundary induced by lateral applied strain is investigated using the phase field crystal model in two dimensions. By studying the growth rate of perturbations, we discover a threshold value of the applied strain below which the instability disappears. Furthermore, we construct the phase diagram of instability which is classified into two groups, namely the grain boundary structural transformation or the dislocation emission, based on the late stage behavior of the grain boundary. A theoretical model is proposed by taking into account a relatively soft solid-solid interface, the elasticity of solid grains, and the interfacial energy of grain boundary. The theoretical prediction of the growth rate and the phase diagram is in quantitatively good agreement with the simulation result. In addition, the theory also explains the inhomogeneous strain distribution observed in simulations.