Enhanced Superplasticity of Ultrafine-Grained Alloys Processed by Severe Plastic Deformation

Nanocrystalline alloys - a boron doped Ni 3 Al, intermetallic and At alloy 1420 (Al-5.5%Mg-2.2%Li-0.12%Zr), as well as submicrocrystalline aluminium alloy 1420 were processed by two severe plastic deformation methods, namely, torsion straining under high imposed pressure and equal channel angular pressing (ECAP). The processed ultrafine-grained (UFG) alloys exhibit enhanced superplasticity at relatively low temperatures and/or high strain rates. From TEM/HREM results the features of superplastic behaviour in UFC alloys and the requirements to achieve enhanced superplasticity are discussed.