Phase field modeling of ideal grain growth in a distorted microstructure

In this work, we perform phase field simulations of ideal grain growth in a distorted polycrystalline aggregate. The distorted microstructure is assumed to be generated by homogenous deformation of an initially equiaxed polycrystalline aggregate. Phase field theory of curvature driven grain boundary migration under distortion is developed and the phase field kinetic relations are implemented in a numerical code based on an explicit time integration procedure. As a benchmark example, phase field simulations of the shrinkage of a distorted circular grain are performed and compared with that of an undistorted elliptical grain to validate the phase field theory and its numerical implementation and also to study the effect of distortion on the kinetics of grain boundary migration. The non-equiaxed distorted grain evolves towards an equiaxed geometry by curvature-driven boundary migration. The evolution rate towards equiaxity is proportional to the distortion magnitude. However, the distortion regardless of its magnitude has no effect on the decrease rate of the distorted grain surface area. We also investigate the evolution of a distorted polycrystalline microstructure by phase field simulations. The elongated distorted grains grow and evolve towards equiaxed grains by ideal grain growth. It has been observed that the distortion influences the directional measure of average grain size to a large extent, but the nondirectional average characteristics of the microstructure are not affected.