Dynamic observation of dislocation-free deformation process in Al, Cu, and Ni thin foils

Abstract

Dislocation-free plastic deformation, which occurs under extraordinarily high internal stress comparable to ideal strength of metals, was discovered in thin foil portion produced by ductile fracture of fcc Au by dynamic observation of the deformation process [1–5]. In the present study, the deformation process of thin foil portion in other fcc metals (Al, Cu, Ni) was examined in the same manner. In all these fcc metals, production of vacancy-type point defect clusters was confirmed during deformation without dislocations. Also, the dislocation-free deformation was found to progress under extraordinarily high internal stress levels corresponding to 14% elastic deformation in Ni, 12% in Cu, and 4% in Al. Especially in Al, as temperature decreased, the number density of stacking fault tetrahedra produced during deformation increased, along with increasing of the detected elastic deformation. These results indicate that internal stress level is a key factor in generalizing the new theory regarding dislocation-free plastic deformation.