Solute effects on the structural and migration behaviour of grain boundaries

One of the most important parameters in grain boundary structure versus property relationships is the solute-boundary interaction involving bulk solute concentrations typically in the ppm range. Experimental studies of such interactions clearly indicate that structural and property differences exist among different high-angle grain boundaries. It is now known that many special or low Sigma CSL grain boundaries (where Sigma is the reciprocal density of coincidence sites) have improved physical and chemical properties relative to general or high Sigma grain boundaries. The low Sigma CSL or ''special'' boundaries are generally for Sigma values less than or equal to 29 with an allowable angular deviation of Delta theta less than or equal to 15 degrees Sigma(-5/6). In this paper, experimental evidence is discussed which demonstrates the significant influence of grain boundary-solute-interactions on the structural and migration differences between low Sigma and general grain boundaries. The relevance of this topic is then considered in relation to grain growth and annealing textures, mesotextures and nanocrystalline metals.