Dislocation-free plastic deformation under high stress

Plastic deformation of crystalline metals not involving dislocations is confirmed to occur during elongation to fracture of thin films, and the possibility of dislocation-free deformation during high-speed deformation of bulk samples is suggested. A general requirement for the occurrence of deformation by the new mechanism is extremely high internal stress that is close to ultimate stress. Current knowledge is presented in a systematically organized manner, and sufficient findings for considering the new mechanism are provided. These include, in the case of thin films, confirmation of the absence of the operation of dislocations, formation of vacancy defects without dependence on temperature or deformation speed, and high internal stress exceeding 10 GPa measured from elastic strain. In the case of high-speed deformation of bulk samples, the findings include the transition of heterogeneous distribution of dislocations at low-speed deformation to random distribution at high-speed deformation, production of vacancy clusters at high density by high-speed deformation, and stress during high-speed deformation being estimated at several 10 GPa. The atomistic mechanism of the new mode of deformation is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.