“…The significant feature of these processes is that the external dimensions of the work-piece do not change significantly during the processing. Examples of these methods include equal channel angular extrusion or pressing (ECAE or ECAP) [3], high pressure torsion (HPT) [4], twist extrusion (TE) [5], friction stir processing (FSP) [6], and multi directional forging (MDF), also known as multiaxial compression/forging (MAC/F) [7]. In addition, there are several methods of producing UFG sheet metals, such as accumulative roll bonding (ARB) [8] and repeated corrugation and straightening (RCS) [9].…”