Producing superplastic ultrafine-grained aluminum alloys through severe plastic deformation

Processing through the introduction of severe plastic deformation (SPD) provides an opportunity to achieve remarkable grain refinement in bulk metals, with as-processed grain sizes lying in the submicrometer or even the nanometer range. Provided these ultrafine grains are reasonably stable at elevated temperatures, these materials are capable of exhibiting very high tensile elongations. Furthermore, since the strain rate in superplasticity varies inversely with the grain size raised to a power of 2, this reduction in grain size leads also to the occurrence of superplastic elongations at high strain rates which are significantly faster than the rates generally associated with superplastic flow. This paper introduces the concept of processing through SPD and describes some representative superplastic results achieved when using aluminum-based alloys.