Severe plastic deformation processes for thin samples

Among the known severe plastic deformation (SPD) techniques, one particular group can be defined as SPD processing of thin samples. Their distinctive feature is that one of the sample dimensions, namely the thickness, is much smaller than the other two dimensions. Examples include High Pressure Torsion and two recently developed techniques: the Cone–Cone Method and the High Pressure Tube Twisting. The mentioned group of SPD processes involve frictional forces acting on the large surfaces and a high hydrostatic pressure within the deformation zone. These techniques are particularly suited for microforming of metals. In this article, we outline the commonalities between these three techniques. The microstructure of copper samples deformed by all the three processes is presented and compared with those obtained by equal-channel angular pressing as a reference bulk forming SPD technique.