Low-temperature superplasticity of Al-Mg-Sc alloy produced by friction stir processing

Ultrafine-grained (0.7 mu m) Al-Mg-Sc alloy with an approximately random misorientation distribution and predominantly high-angle boundaries of 97% was produced by friction stir processing. A ductility of 235% was obtained at 200 degrees C. Increasing temperature from 200 to 300 degrees C resulted in an increase in superplasticity, optimum strain rate and strain rate sensitivity. Low temperature and high strain rate superplasticity with a ductility of 620% was achieved at 300 degrees C and 3 x 10(-2) s(-1). Abnormal grain growth occurred at 350 degrees C, resulting in the disappearance of superplasticity. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.