Abstract: The microstructure and texture in a commercially processed Al-6 wt% Cu-0.4 wt% Zr (Supral100) aluminium alloy have been investigated after annealing and hot tensile straining at 450 °C, using a field emission gun scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The microstructure of commercially processed alloy had a relatively large fraction of high angle grain boundaries (HAGBs) which were aligned parallel to the rolling direction, and a strong texture. Annealing at 450 °C led to an increase in the fraction of HAGBs and to an increase in HAGB spacing and these changes were progressively enhanced by subsequent tensile deformation. The increasing fraction of HAGBs was due to the annihilation of low
angle grain boundaries (LAGBs). A sharpening of texture during annealing was attributed to preferential textural growth, and the reduction of texture at higher tensile strains led to the development of superplastic behaviour. The present work supports the view that the evolution of the fine grain microstructure during the high temperature straining of Supral100 is primarily due to the accumulation of a large area of grain boundary during the initial thermomechanical processing, and does not involve any unusual restoration processes.

Key words: Aluminium, Superplastic deformation, Microstructure, Texture, Electron backscatter diffraction