SUPERPLASTIC BEHAVIOR OF COARSE-GRAINED Al-Mg ALLOY

Abstract

This paper concentrates on the study of the superplastic response of coarse-grained Al - Mg alloys under uniaxial tension at different temperatures (ranging from 400°C to 525°C) and strain rates (10 -2 S -1 , 10 -3 S -1 & 10 -4 S -1 ). The microstructures have been analyzed using optical (OM) and transmission electron microscopy (TEM). It has been observed that continuous re-crystallization occurs during hot deformation of the alloy at the temperature of 425°C and strain rate of 10 -2 S -1 . At the temperature of 425°C and strain rate of 3.78×10 -3 S -1 , this Al - Mg alloy has the maximum elongation to failure of 181%, which is sufficient for manufacturing of extremely complex shapes using superplastic forming technology. The constant strain rate sensitivity index m and TEM observations show that in this case deformation mechanism involved is dislocation glide. Recrystallization during the hot tension greatly enhanced the plasticity of the coarse-grained material at a strain rate of about 10 -2 S -1 and the maximum elongation changes as a function of the strain rate.