Hardening mechanisms at grain boundaries: a microscopic approach

2014 Grain-boundary induced hardening mechanisms are illustrated by recent observations in silicon bicrystals. Basic features of grain boundary structure and grain boundary dislocations are given in the case of the 03A3 = 9 twin boundary. The dissociation of dislocations in grain boundaries and the possibility of direct dislocation transmission from one crystal to the other across the interface are discussed. At moderate temperatures, such mechanisms are difficult and not able to prevent the formation of work hardened regions in the neighbourhood of grain boundaries, right at the onset of plastic deformation. Those regions contain networks with Lomer-Cottrell locks and show evidence of profuse cross-slip. Large stress concentrations arise, that may be against the applied stress. The relevance of these findings for other kinds of grain boundaries and other materials is briefly discussed. Revue Phys. Appl. 23 (1988) 479-490 AVRIL 1988, Classification Physics Abstracts 61.70 62.20F 81.40L