Superplastic behavior of an Al-Mg alloy at elevated temperatures

The superplastic properties and microstructural evolution of a 0.2% Zr and 1.6% Mn modified 5083 aluminum alloy with an initial grain size of 6.2 mum were examined at strain rates ranging from 10(-5) to 10(-1) s(-1) in the temperature interval 500-580 degreesC. The maximum elongation-to-failure of 1150% was found at 570 degreesC, which is near the solidus temperature of 572 degreesC,and an initial strain rate of 2.8 x 10(-3) s(-1). The corresponding strain rate sensitivity coefficient, m, was about 0.6. It was shown that increasing the temperature from 550 to 570 degreesC results in reduced cavitation and expanding the optimal interval of superplasticity toward lower strain rates due to the disappearance of the threshold stress. The influence of temperature on the mechanisms of superplastic deformation is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.