Plastic Relaxation at Crack Tip: from Brittle to Ductile Behaviour

Abstract

Experimental analysis of plastic zone growth in silicon have recently underlined the fact that two different populations of dislocations sources have to be considered. A small number of primary ones, linked to defects of the crack front, emit tens of dislocations in primary planes. A large number of secondary ones, resulting from cross-slip of primary dislocations coupled with the mechanism of stimulated emission, only emit a few dislocations. This paper shows that primary dislocations cannot account for observed brittle to ductile transition.