Effect of ultrasonic melt treatment on the refinement of primary Al3Ti intermetallic in an Al-0.4Ti alloy

High intensity ultrasonic melt treatment was applied to an Al-0.4 wt% Ti alloy over three selected temperature ranges: 810 to 770 °C (above liquidus), 770 to 730 °C (across liquidus), and 730 to 690 °C (below liquidus). The size and morphology of the primary Al3Ti intermetallic particles were studied by scanning electron microscopy. It was found that the primary Al3Ti intermetallics were refined as a result of ultrasonication over all three temperature ranges and their morphology changed from typical large dendritic plates to small compact tablets. Quenching experiments before and after the ultrasonication were also carried out to capture the high-temperature stage of intermetallic formation. Based on the size and morphology observations, the mechanisms for the refinement of primary Al3Ti intermetallics at different solidification stages are discussed.