Evolution of defect substructure of metal alloys at microscopic and mesoscopic level under torsion

Transmission electron microscopy was used to investigate the reorientation of crystal lattice during the formation of ultrafine-grained (UFG) copper, nickel, and an alloy of Ni-18% Al-8% Cr-1% Zr-0.15% B (at.%) under severe p lastic deformation by equal-channel angular (ECA) pressing and twisting at a high quasi-hydrostatic pressure. The crystal lattice was found to transfo rm into a UFG state; it is fragmented at the nano-, micro-, and mesoscale l evels. Possible mechanisms for the reorientation of the crystal lattice und er deformation at the micro- and mesoscale level are discussed. (C) 2001 Pu blished by Elsevier Science Ltd.