Severe plastic deformation (SPD) processes for metals

Processes of severe plastic deformation (SPD) are defined as metal forming processes in which a very large plastic strain is imposed on a bulk process in order to make an ultra-fine grained metal. The objective of the SPD processes for creating ultra-fine grained metal is to produce lightweight parts by using high strength metal for the safety and reliability of micro-parts and for environmental harmony. In this keynote paper, the fabrication process of equal channel angular pressing (ECAP), accumulative rollbonding (ARB), high pressure torsion (HPT), and others are introduced, and the properties of metals processed by the SPD processes are shown. Moreover, the combined processes developed recently are also explained. Finally, the applications of the ultra-fine grained (UFG) metals are discussed

An analysis for the effect of a grain size gradient on torsional and tensile properties

To understand the flow stress behavior of a grain size gradient structure, generalized stress and strain relationships in both torsion and tension are analyzed in terms of continuum mechanics. The results show that the twisting moment in torsion and flow strength in tension increase when the grain size decreases as a function of the radial distance in a cylindrical specimen. For experimental comparison, a grain size gradient is produced, through a thermomechanical process of torsioning and annealing, in a mild carbon steel of AISI 1018. The effect of the gradient structure is then tested for both torsional and tensile properties of the steel. © 1988 The Metallurgical Society of AIME