Variations in microstructure and texture during high temperature deformation of Al–Mg alloy

The effect of strain rate on the superplastic deformation of a fine-grained aluminium–magnesium alloy has been investigated. Microstructural transformations were quantified by crystallographic texture, the study of the size of the grains, their morphology and their spatial distribution. At low strain rate a progressive reduction of the initial texture is observed, resulting from the predominance of grain boundary sliding. But even for large strains the texture randomisation is not complete, which confirms the role played by dislocation creep in superplasticity of the alloy. At high strain rate textural components of plasticity develop and the grains become elongated along the tensile direction. Nevertheless, transmission electron microscopy observations and a calculation of the expected variation with strain of the shape of the grains, suggest that continuous recrystallisation is likely to take place during deformation.