Prof. Megumi Kawasaki
Division of Materials Science and Engineering
Hanyang University, South Korea
Processing of metals through the application of severe plastic deformation (SPD) provides an opportunity for achieving ultrafine grains in the sub-micrometer or even the nanometer range. These grains in the bulk metals usually show superior mechanical and physical properties. In practice, the strength at ambient temperatures is dictated through the Hall-Petch relationship in which the yield stress varies inversely with the grain size raised to a power of one-half, so that strength increases as the grain size is reduced. At high temperatures, in the regime where diffusion becomes important, there is a potential for achieving superplastic flow and a superplastic forming capability in materials having very small grain sizes. Several SPD methods are now available but the most promising appear to be High-Pressure Torsion (HPT). This presentation examines the procedure with special emphasis on evolution of microstructure and the mechanical properties of the ultrafine-grained (UFG) materials and bulk nanostructured materials (BNM) processed by the SPD technique. Moreover, recent experimental findings are suggesting a potential for simply and expeditiously fabricating a wide range of metal-matrix nanocomposites through HPT.