Processing of Ultrafine-Grained Materials through the Application of Severe Plastic Deformation

Processing through the application of severe plastic deformation (SPD) has become an absorbing tool because it provides the potential for refining the grain size of polycrystalline bulk metals to the submicrometer or even the nanometer level. Several SPD methods are now available, but the more promising procedures seem to be equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). This report examines these procedures with an emphasis on the principles of grain refinement and the mechanical properties developed at high temperatures in materials after processing by ECAP and the hardness homogeneity and microstructural evolution in materials processed by HPT. Moreover, recent observations on the ECAP and HPT processing also are discussed.