Generation of vacancies in high-speed plastic deformation

In a recent experiment, crystalline metals were subjected to high-speed plastic deformation, and subsequently a number of vacancy clusters were observed without any trace of dislocations. In an effort to explain this result, in the present study fluid-like behavior of solid in ultra-high-speed deformation is considered, and the possibility of spontaneous generation of vacancies analogous to cavitation in high-speed fluid flow is discussed. Similar to a large velocity gradient that induces turbulence in a high-speed fluid flow, large shear stress induced in a solid material during the course of high-speed deformation may generate vacancies instead of dislocations, if the dislocations cannot follow the deformation speed. In this paper, similarities between dislocation in solid and vortex in a fluid discussed, along with similarities between vacancy in a solid and cavitation in fluid, and a mechanism of vacancy production under high-speed plastic deformation of crystalline materials is proposed.