GRAIN-GROWTH BEHAVIOR OF THE AL-CU EUTECTIC ALLOY DURING SUPERPLASTIC DEFORMATION

Grain growth behaviour of the Al-Cu eutectic alloy was investigated as a function of strain (epsilon), strain rate (epsilon) and deformation temperature (T) over epsilon = 10(-5) to 10(-2) s-1 and T = 400 to 540-degrees-C. The grain size increases with increase in strain and temperature. Upon deformation to a fixed strain, the grain growth is generally seen to be more at lower strain rates. The rates of overall grain growth (d-epsilon,t) and due to deformation alone (d-epsilon), however, increase with increasing strain rate according to d-epsilon,t is proportional to epsilon-0.86 and d-epsilon is proportional to-0.64, respectively. The increase in the grain growth rate with strain rate is attributed primarily to the shorter time involved at higher strain rate for reaching a fixed strain. The activation energy for grain growth under superplastic conditions is estimated to be 79 kJ mol-1