Effect of ZrO2 incorporation on the mechanical behavior of an AlSi alloy

AlSi-ZrO2 composite was prepared by stir casting method using a vortex technique. Micrograph observations exhibit a microstructure containing primary Si particles, eutectic silicon cells and intermetallic particles embedded in a dendritic primary alpha-phase in both Al-Si and AlSi-ZrO2 homogenized alloys. Difference in thermal conductivity between the alpha matrix and the ZrO2 particles generates a high temperature gradient resulting in an increase in the cooling rate which affects the microstructure and, consequently, the mechanical properties. On the other hand, the difference of the structures and the thermal expansion coefficient between ZrO2 particles and the matrix generates stress and increases the dislocation density. Presence of the ZrO2 particles enhances the ductility of the composite materials and reduces its Young's modulus. Addition of the ZrO2 particles increases the hardness of the composite materials at low aging temperature and reduces it at higher aging temperature.