On the Conflicts in the Experimental Results Concerning the Mechanical Properties of Ultra-Fine Grained and Nanostructured Materials: Effects of Processing Routes and Experimental Conditions

Abstract

Different routes of severe plastic deformation (SPD) processing employed for the production of ultrafine grained and nanostructured materials are identified. The structural changes accompanying SPD that lead to improved mechanical properties are noted. Some uncertainties associated with the processing, which cause variations in the mechanical properties, are highlighted. Special attention is paid to equi-channel angular pressing/ extrusion, high pressure torsion, accumulative roll bonding/fold - roll processing, reciprocating extrusion – compression, cyclic close die forging, and repetitive corrugation and straightening- processes many of which can be adapted to suit standard metal working equipment, fitted with inexpensive devices and tools. The conflicting observations on the mechanical properties of ultrafine grained and nanostructured materials are discussed.