Influence of fine particles on grain coarsening within an orientation gradient

A simple model of grain coarsening is presented that takes into account the influence of both an orientation gradient within the microstructure and a dispersion of fine particles on the kinetics of grain coarsening. The model is used to illustrate the substantial influence of fine particles on grain coarsening whereby, in a particle-free system, grains within a large orientation gradient grow rapidly whereas a system containing a large volume fraction of fine particles results in very limited coarsening, despite the presence of the orientation gradient. The model is used in conjunction with the analysis of grain coarsening in some aluminium alloys where deformation was found to generate a range of microstructural inhomogeneities such as either deformation bands in hot deformed {1 0 0}〈0 0 1〉 Al-0.05%Si single crystals or a microstructure consisting of colonies of either low angle or high angle grain boundaries in a severely strained particle-containing Al-0.2%Sc alloy. The simulations using the model are found to be in broad agreement with the experimental observations of grain coarsening in these alloy systems.