In-situ observations and acoustic measurements upon fragmentation of free-floating intermetallics under ultrasonic cavitation in water

Ultrason Sonochem. 2021 Nov 2;80:105820. doi: 10.1016/j.ultsonch.2021.105820. Online ahead of print.ABSTRACTGrain refinement in alloys is a well-known effect of ultrasonic melt processing. Fragmentation of primary crystals by cavitation-induced action in liquid metals is considered as one of the main driving mechanisms for producing finer and equiaxed grain structures. However, in-situ observations of the fragmentation process are generally complex and difficult to follow in opaque liquid metals, especially for the free-floating crystals. In the present study, we develop a transparent test rig to observe in real time the fragmentation potential of free-floating primary Al3Zr particles under ultrasonic excitation in water (an established analogue medium to liquid aluminium for cavitation studies). An effective treatment domain was identified and fragmentation time determined using acoustic pressure field mapping. For the first time, real-time high-speed imaging captured the dynamic interaction of shock waves from the collapsing bubbles with floating intermetallic particles that led to their fragmentation. The breakage sequence as well as the cavitation erosion pattern were studied by means of post-treatment microscopic characterisation of the fragments. Fragment size distribution and crack patterns on the fractured surface were then analysed and quantified. Application of ultrasound is shown to rapidly (<10 s) reduce intermetallic size (from 5 mm down to 10 μm), thereby in...

Source: Ultrasonics Sonochemistry - November 11, 2021 Category: Chemistry Authors: Abhinav Priyadarshi Mohammad Khavari Shazamin Bin Shahrani Tungky Subroto Lukman A Yusuf Marcello Conte Paul Prentice Koulis Pericleous Dmitry Eskin Iakovos Tzanakis Source Type: research