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 transform ations were quantified by crystallographic texture, the study of the size o f the grains, their morphology and their spatial distribution. At low strai n rate a progressive reduction of the initial texture is observed, resultin g from the predominance of grain boundary sliding. But even for large strai ns the texture randomisation is not complete, which confirms the role playe d by dislocation creep in superplasticity of the ahoy. At high strain rate textural components of plasticity develop and the grains become elongated a long 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 t o take place during deformation. (C) 2001 Elsevier Science B.V. Ail rights reserved.