Irreversibility and the statistics of grain boundaries

For most coarsening systems, we do not understand how or why the evolution produces a statistical steady state. In a paper appearing in Physical Review B, Katayun Barmak at Carnegie Mellon University and colleagues present theoretical arguments to explain the statistics of grain boundaries in a polycrystalline material after the occurrence of coarsening due to annealing [1]. Recent experimental [2] and numerical [3] work involving some of the same authors has shown that coarsening drives the statistics of grain boundaries to a Boltzmann distribution. The work of Barmak et al. offers an explanation for this behavior based on the presence of occasional irreversible changes to the grain boundary network. Their argument seems rather general and should also be relevant to other systems. From a technological standpoint, understanding coarsening in materials is important, since the physical properties of a material depend on its microstructure.