Superplasticity in aluminium-silicon eutectic

Abstract

Superplastic behaviour in hot rolled AI-Si eutectic was investigated, for a grain size of 18 μm, over a range of strain rates, temperatures, and compositions. The AI-Si eutectic was successful in producing superplasticity with over 300% elongation. Two dominant superplasticity mechanisms seem to operate: a dislocation climb at high strain rates and b grain boundary sliding with diffusional accommodation at intermediate and low strain rate. The calculations of strain rate and activation energy support this contention. In addition, the contribution of the imposed strain to the total ductility and to the strain rate sensitivity was also studied. The results indicate that superplasticity in eutectic AI-Si is severely restricted by structural coarsening at large strains, particularly at the lower strain rates.