The use of severe plastic deformation for microstructural control

The microstructure of a metal may be very significantly changed by subjecting the material to severe plastic deformation (SPD) through procedures such as equal-channel angular pressing (ECAP) and high-pressure torsion. These procedures lead to a substantial refinement in the grain size so that the grains are reduced to, typically, the submicrometer or even the nanometer range. This paper describes the application of SPD to pure aluminum and aluminum-based alloys, with emphasis on the factors influencing the development of homogeneous microstructures of equiaxed grains separated by high-angle grain boundaries. Materials subjected to ECAP are capable of exhibiting exceptional mechanical properties including superplastic ductilities at very rapid strain rates. Examples of this behavior are presented and results are described showing the potential for using this approach in superplastic forming applications at high strain rates.