Microstructure evolution of eutectic Si in Al-7Si binary alloy by heat treatment and its effect on enhancing thermal conductivity

Heat treatment is one of the most effective controlling factors used to improve the thermal conductivity (TC) of any alloy castings. In this work, the microstructure of the Al-7Si binary alloy modified by heat treatment at 520 °C for 1−48 h was reported. Both size and shape of the eutectic Si particles are affected by the heat treatment process. Optical microscopy (OM), scanning electron microscopy (SEM) and X-Ray diffraction (XRD) analysis were carried out to characterize the eutectic Si phase transformation. The acicular-shaped eutectic `Si particles were broken into smaller segments and gradually spheroidized. The TC of the alloy heat treated for 12 h increases by 10.5% compared to the as-cast alloy. The correlation between the TC performance and the morphology of eutectic Si phases is detailed discussed.