Combined effects of cobalt addition and ultrasonic vibration on microstructure and mechanical properties of hypereutectic Al-Si alloys with 0.7% Fe

► Morphology and compositions of (Fe + Co)-bearing compounds were studied. ► Combined effects of ultrasonic vibration and cobalt content were investigated. ► The optimum Co:Fe ratio in Al-20Si alloy was proposed. ► The tensile strength at both room and elevated temperature were tested.