Effect of temperature and displacement rate on behaviour of as-cast AA5182 and Al–3·3%Cu alloys under tensile loading near solidus temperature

Hot cracking develops in the still semi-solid casting during the last stages of solidification. The micro-mechanism of its origin is not generally accepted. There exists considerable doubt whether it is initiated by a void or develops as an instantaneous crack. The aim of this work is to study the mechanism of fracture behaviour of aluminum alloys around solidus temperature. Tensile tests were performed on notched specimens of as-cast AA5182 and Al–3·3%Cu alloys using a Gleeble 3500 thermomechanical simulator. The effect of temperature and strain rate on the propagation of fracture in the semi-solid state has been studied to establish fracture mechanism. The transition from ductile to brittle mode of fracture has been observed around the solidus temperature. The fracture is intergranular and propagates through interdendritic channels.