High-speed heavy plastic deformation of thin foils of face-centered cubic metals, including Al, was found to produce a high density of small vacancy clusters in the form of stacking-fault tetrahedra. The dependence of the cluster density upon the deformation temperature and deformation rate indicated the production of vacancy clusters from deformation-induced dispersed vacancies. Neither dislocations, nor any indication of dislocation reactions, were detected in the regions which contained a high density of vacancy clusters. A possible model was proposed which described, for the extremely high strain rates where dislocation generation was difficult, how a high concentration of point defects was produced by a large number of parallel shifts of atomic planes without dislocations.

Anomalous Production of Vacancy Clusters and the Possibility of Plastic Deformation of Crystalline Metals without Dislocations. M.Kiritani, Y.Satoh, Y.Kizuka, K.Arakawa, Y.Ogasawara, S.Arai, Y.Shimomura: Philosophical Magazine Letters, 1999, 79[10], 797-804