Diffusion creep and superplasticity in aluminium alloys

The plastic deformation of two classes of fine-grained aluminium alloys at elevated temperatures and slow strain rates have been investigated. One class of material, Al–Cu–Zr, was processed to develop banded microstructures; the other class, based on Al–(Mg)–Mn, had near-equiaxed microstructures. In both classes, superplastic behaviour was found in the variants with the higher solute content. The evolution of the banded microstructures and the results from surface grid measurement in the Al–(Mg)–Mn alloys give results which indicate that the superplasticity is primarily a result of diffusion creep, and the effect of solute is proposed to be via an enhancement of solvent self-diffusion.