Dynamic evolution of fine grained structure and superplasticity of 7075 aluminum alloy

Hot deformation of an unrecrystallized 7075 aluminum alloy was studied by means of 2-step tensile testing and metallographic observations. Typical superplasticity took place accompanied with the evolution of new fine grains in the medium region of strain rate. Grain boundary sliding (GBS) operated just after yielding even in the unrecrystallized coarse grained structure. It is concluded from the mechanical and metallographic results that GBS can play a key role in the evolution of fine grains as well as the appearance of superplasticity.