LXX. The markings in the cleavage surfaces of zinc single crystals

Summary Zinc single crystals of various orientations were broken by applied tensile stresses at -196°c. The two faces of the cleavage fracture were examined and compared ; in general they differed markedly. It was noted that the cleavage crack tends to propagate along the active slip direction, and that the distribution of the twins and kink bands is related to the region of the origin of the fracture and to the direction of crack propagation. The majority of the observations on the twins are entirely in accord with the theory of Bilby and Bullough (1954), although more experimental work is necessary to clarify some points where there are discrepancies. In the case of the kink bands, however, there is little agreement between the observations and the theoretical results.