Behavior of Al-Zr intermetallic compound particles under high-amplitude ultrasound irradiation into molten aluminum

Free surface entrainment of oxide particles and their role in ultrasonic treatment performance of aluminum alloys

“…2 , the liquidus temperature (T L ) of Al-0.4 %Zr alloy was approximately 1073 K. Therefore, UST was performed above T L . More details can be found in our earlier publication [33] .

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An overview and critical assessment of the mechanisms of microstructural refinement during ultrasonic solidification of metals

“…Due to a relatively larger liquid fraction, cavitation and acoustic streaming-induced fragmentation mechanisms are expected to dominate the refinement of the primary intermetallic phases during UST [43] , [73] . There are few prominent alloy systems in Al and Mg alloys that solidify with primary crystalline or intermetallic phases, including primary Si [103] , [104] , Al 3 Zr [105] , Al 3 Ti [106] , Al-Zr-Ti [107] , Al 3 Fe [73] , Al 3 Ni [73] , α/β- Fe intermetallics [108] and those with grain refiner particles such as TiB 2 in Al alloys and Zr particles in Mg alloys [43] . In addition to the fragmentation effects, activation of oxide particles has also been considered as one of the possible mechanisms [43] , [106] .…”

“…It is worth noting that reducing UST time from UST-2 (4 min) to UST-3 (2 min) for a constant cooling rate (4.0 °C/s) also produces similar refinement, indicating that finer phases are associated with faster precipitation at the onset of solidification and separation by acoustic streaming. Since the activity of cavitation events is found to decrease exponentially with respect to the distance from the sonotrode [105] , [109] , intermetallic refinement is controlled by cooling rate and acoustic streaming-induced fluid flow.…”