An evaluation of the flow behavior during high strain rate superplasticity in an Al-Mg-Se alloy

An Al-3 pet Mg-0.2 pet Sc alloy was fabricated by casting and subjected to equal-channel angular pressing to reduce the grain size to similar to0.2 mum. Very high tensile elongations were achieved in this alloy at temperatures over the range from 573 to 723 K, with elongations up to >2000 pet at temperatures of 673 and 723 K and strain rates at and above 10(-2) s(-1). By contrast, samples of the same alloy subjected to cold rolling (CR) yielded elongations to failure of <400 pet at 673 K. An analysis of the experimental data for the equal-channel angular (ECA)-pressed samples shows consistency with conventional superplasticity including an activation energy for superplastic flow which is within the range anticipated for grain boundary diffusion in pure Al and interdiffusion in Al-Mg solid solution alloys.