Processing and properties of bulk ultrafine-grained materials produced through severe plastic deformation

Very substantial grain refinement, to the submicrometer or nanometer level, may be achieved in bulk metallic alloys through processing using techniques associated with the introduction of severe plastic deformation (SPD). Procedures available for SPD include Equal-Channel Angular Pressing (ECAP) where a sample is pressed through a die constrained within a channel bent through an angle at, or very close to, 90° and High-Pressure Torsion (HPT) where the sample, in the form of a thin disk, is subjected to a high pressure and concurrent torsional straining. This paper reviews the two processes of ECAP and HPT and describes representative results. It is demonstrated that processing by SPD provides a potential for achieving exceptional properties in bulk solids.