Grain boundary sliding and crystallographic slip during superplasticity of Al-5%Ca-5%Zn as studied by texture analysis

The contribution of crystallographic slip (CS) and grain boundary sliding (GBS) during superplastic deformation of Al-5 wt.% Ca-5 wt.% Zn at 10(-2) s(-1) in the temperature range of 300-550 degrees C is discussed on the basis of texture evolution. During deformation in the transverse direction, the initial rolling texture component in the mid-layer, {225}[554] (C-type), changes dramatically and the brass component, {011}[211], appears. It is shown that this change is gradual and can be associated with an 'equivalent' single slip in the (111)[211] slip system. It can be inferred from this study that both GBS and CS take place during superplastic deformation of this alloy. Quantitative evaluation of the volume fraction of crystallites (F-v) associated with texture components indicates that the testing temperature strongly influences the contribution of each of these mechanisms. The importance of GBS increases with temperature. Continuous recrystallization and (sub)grain growth, which also occur during deformation, must also be taken into consideration for a complete description of the microstructural evolution which occurs during superplastic deformation of this alloy. (C) 1998 Elsevier Science S.A. All rights reserved.