Grain growth behaviour of the Al-Cu eutectic alloy during superplastic deformation

Abstract

Grain growth behaviour of the Al-Cu eutectic alloy was investigated as a function of strain (ε), strain rate $(\dot \varepsilon )$ and deformation temperature (T) over $\dot \varepsilon$ = 10⁻² s⁻¹ and T=400 to 540°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 $(\dot d_{\varepsilon ,t} )$ and due to deformation alone $(\dot d_\varepsilon )$, however, increase with increasing strain rate according to $\dot d_{\varepsilon ,t} \propto \dot \varepsilon ^{0.86}$ and $\dot d_{\varepsilon ,t} \propto \dot \varepsilon ^{0.64}$, 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.