Increasing the thermal diffusivity of Al-Si-Mg alloys by heat treatment

The objective of this study is to increase the thermal diffusivity of Al-Si-Mg alloys by heat treatment and demonstrate the effect of the eutectic phase distribution on thermal conductivity of Al-Mg-Si alloys. Two types of Al-Si-Mg (Al-0.2Si-0.4Mg and Al-6.5Si-0.4Mg) alloys used in this study were prepared through atmospheric gravity casting. Solid solution treatment was performed at 535 degrees C for 4-10 h and then quenched in warm water of 80 degrees C temperature. Artificial aging of specimens was performed at 180 degrees C for 5 h. After aging treatment, the changes of microstructures due to heat treatment were examined by using optical microscopy. Differential scanning calorimeter analyzed phase transform during the heat treatment. Variations of thermal diffusivity according to the microstructures were investigated by using a laser flash apparatus. Precipitation of Mg2Si and Si phases increased the thermal diffusivity after aging treatment. Moreover, thermal diffusivity of the Al-6.5Si-0.4Mg alloys also increased with increasing solid solution treatment time due to spheroidization of eutectic Si.