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

Recent trends in the aluminum industry toward increasing the recycling rate of aluminum alloys have led to difficulties in controlling the formation of intermetallic compounds (IMCs). The up-to-date investigations have revealed that ultrasonic irradiation is a promising tool to refine and modify the intermetallic compounds formed in the melt before or during casting, and the reported mechanisms include ultrasound-assisted nucleation and fragmentation of compounds. This work presents results concerning the modification effect of ultrasound on model Al3Zr compounds with emphasis on the effect of vibration amplitudes. The results reveal that needle-like Al3Zr compounds can be significantly modified to thicker shape when amplitude increases from 38 µm to 48 µm, and then change to more rounded shape with the further increase of amplitude. Theoretical consideration and numerical simulation show that in addition to the above-mentioned mechanisms, cavitation-induced heat generation and mircrojet-driven mass transfer are also of prime importance in controlling the morphology and growth of IMCs.