Nanocrystalline materials were characterized by ultra-fine crystallites separated by grain boundaries. The dislocations in the crystallites of nanocrystalline materials form some special configurations and the dislocation density drastically decreased. A model was proposed to account for the effects of the defects in the grain boundaries of nanocrystalline materials on the dislocation stability and configuration in the crystallites. Based on the fact that the grain boundaries of nanocrystalline materials contain a large number of vacancies and vacancy clusters, a 1/x3 law for the stress field induced by the vacancies and the vacancy clusters was considered. The region of the dislocation stability in the crystallites was estimated and the dislocation configurations in the crystallites were deduced. The theoretical results were shown to interpret the experimental observations well.

Dislocation Stability and Configuration in the Crystallites of Nanocrystalline Materials. W.Qin, Y.W.Du, Z.H.Chen, W.L.Gao: Journal of Alloys and Compounds, 2002, 337[1-2], 168-71