The method of ECAP (equal channel angular pressing), which achieves to prepare bulk nanostructured materials, was developed by prof. Segal et al in 1980s. Samples after repeated ECAP can meet a number of requirements as following: (1) ultra fine-grained structure are obtained with prevailing high-angle grain boundaries; (2) The ultra fine structure is uniform in the whole volume and the properties of the processed materials are stable;(3) The ECAPed samples avoid mechanism damage and cracks....