ALTERNATIVE LENGTH SCALES FOR POLYCRYSTALLINE MATERIALS .1. MICROSTRUCTURE EVOLUTION

It is a well-documented experimental observation that properties of grain boundaries depend on the atomic structure of the boundary. Yet constitutive relations for properties of polycrystalline materials containing a variety of grain boundaries currently do not take account of this boundary-to-boundary variability. Instead, a single-length scale-the average grain diameter-is utilized with the underlying assumption that all grain boundaries are the same. In this (I) and the following paper (II), we extend the accepted viewpoint to encompass a binary classification of grain boundaries based on their misorientation angle. The resultant new length scale is that associated with clusters of grains linked by grain boundaries sharing misorientations in the same category. This first paper focuses on how a model polycrystal is generated, the energetics of the model, and its evolution under various external influences.