Effect of ultrasonic treatment on solidification structure refinement of Mg-Al binary alloy

The test-equipment of ultrasonic treatment and the accessory equipments were designed and used. The effect of ultrasonic treatment on microstructure of Mg-Al alloy was investigated. The experiment results show that the microstructures of Mg-Al alloy treated by ultrasonic are significantly refined. The dendrite morphology of the primary phase in Mg-Al binary alloys is changed and the fine globular equiaxed grains are formed. The network of β-Mg17Al12 phase distributed on grain boundary is discontinuous in Mg-Al binary alloy with ultrasonic treatment. The refining degree of the primary phase and β-Mg17Al12 phase in Mg-Al binary alloy with different Al content is different after solidification of Mg-Al binary alloys with ultrasonic treatment. Ultrasonic treatment dramatically changed the processes of heat and mass transfer in the melt, affected the nucleation and growth of crystals, and hence refined the solidification microstructure of magnesium alloys. The results also confirm that ultrasonic treatment of magnesium melt will be a new method for the grain refinement of magnesium alloys.