LAUSR

Abstract The microstructure and tensile property of the hypoeutectic Al-Si alloy with and without microalloying of Sc and Zr were studied by means of the optical microscope (OM), Transmission electron microscopy (TEM) and the tensile test. The focus of this work is the effect of microalloying and tensile deformation on the internal structure (i.e. nanoscale precipitates and the stacking faults) in eutectic Si phase. The results show that the nanoscale precipitates are evident in eutectic Si phase in Al-Si alloy without any special heat treatment or modification. The additions of Sc and Zr into the Al-Si alloy increased the size of the nano precipitates, and significantly promoted the formation of the stacking faults inside the eutectic Si phase. Moreover, the eutectic Si phase experienced twinning deformation during the tensile deformation of the Al-Si based alloy, and this twinning deformation was more pronounced with increasing the tensile strength of the Al-Si based alloy. It is proposed that the deformation of the eutectic Si phase also contributed to the property and the ductility of the Al-Si based alloy.