The characteristics of grain refinement in materials processed by severe plastic deformation

Processing by severe plastic deformation (SPD) provides the opportunity to achieve remarkable grain refinement in bulk crystalline solids. Typically, materials processed by SPD have grain sizes in the submicrometer or nanometer range. Several different SPD processing techniques are now available but the procedure currently receiving the most attention is equalchannel angular pressing (ECAP). In processing by ECAP, it is possible to obtain detailed information on the nature of grain refinement from systematic experiments conducted on single crystals and polycrystalline samples. This paper describes the types of results obtained when ECAP is applied to single crystal and polycrystalline aluminum. It is shown that the experimental results are consistent with expectations based on analyses of the processing behavior. The results permit the development of a simple model describing grain refinement in ECAP.