Ultrasonic melt processing in the low pressure investment casting of Al alloys

AlSi7Mg investment cast test bars were produced using low-pressure die casting and ultrasonically refined during cooling. The microstructure and mechanical properties of the samples at different distances from the acoustic radiator were characterized for 650 °C pouring temperature. The combined technique lead to cast samples free from gas porosities and solidification defects, promoted the formation of small α-Al globular grains, modified the eutectic silicon, dispersed and decreased the size of intermetallic phases. The alloy mechanical properties were improved, increasing the ultimate tensile strength, yield strength and strain.