Advances in Superplasticity of Ultrafine-Grained Alloys: Recent Research and Development

Recent studies have revealed that ultrafine-grained (UFG) metals and alloys produced by severe plastic deformation (SPD) can demonstrate extraordinary superplasticity at low temperatures and/or high strain rates. This work presents new results on superplasticity in several UFG Al and Ti alloys focusing on microstructural evolution and strain hardening, as well as the challenges of their application. Grain refinement in these alloys was accomplished using severe plastic deformation techniques, including new modifications of equal channel angular pressing (ECAP). Unusual behavior of UFG alloys originates both from the formation of ultrafine grain by SPD processing as well as the state of grain boundaries in these materials. It is established that superplastic deformation allowed not only to attain their efficient forming, but also to improve the ultrafine-grained structure and to obtain enhanced mechanical properties in the articles produced. The results demonstrate the possibilities of new applications of superplastic forming using bulk nanostructured materials.