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Instruments / Technical Area	Publication Details	Published
I12-JEEP: Joint Engineering, Environmental and Processing	Fundamental studies of ultrasonic melt processing D. G. Eskin , I. Tzanakis , F. Wang , G. S. B. Lebon , T. Subroto , K. Pericleous , J. Mi Ultrasonics Sonochemistry 52, 455-467 DOI: 10.1016/j.ultsonch.2018.12.028 Diamond Proposal Number(s): [8542, 12131] Open Access Show Abstract ▼ Abstract: Ultrasonic (cavitation) melt processing attracts considerable interest from both academic and industrial communities as a promising route to provide clean, environment friendly and energy efficient solutions for some of the core issues of the metal casting industry, such as improving melt quality and providing structure refinement. In the last 5 years, the authors undertook an extensive research programme into fundamental mechanisms of cavitation melt processing using state-of-the-art and unique facilities and methodologies. This overview summarises the recent results on the evaluation of acoustic pressure and melt flows in the treated melt, direct observations and quantitative analysis of cavitation in liquid aluminium alloys, in-situ and ex-situ studies of the nucleation, growth and fragmentation of intermetallics, and de-agglomeration of particles. These results provide valuable new insights and knowledge that are essential for upscaling ultrasonic melt processing to industrial level.	Apr 2019
	In-situ observation of ultrasonic cavitation-induced fragmentation of the primary crystals formed in Al alloys Feng Wang , Iakovos Tzanakis , Dmitry Eskin , Jiawei Mi , Thomas Connolley Ultrasonics Sonochemistry DOI: 10.1016/j.ultsonch.2017.03.057 Open Access Show Abstract ▼ Abstract: The cavitation-induced fragmentation of primary crystals formed in Al alloys were investigated for the first time by high-speed imaging using a novel experimental approach. Three representative primary crystal types, Al3Ti, Si and Al3V with different morphologies and mechanical properties were first extracted by deep etching of the corresponding Al alloys and then subjected to ultrasonic cavitation processing in distilled water. The dynamic interaction between the cavitation bubbles and primary crystals was imaged in-situ and in real time. Based on the recorded image sequences, the fragmentation mechanisms of primary crystals were studied. It was found that there are three major mechanisms by which the primary crystals were fragmented by cavitation bubbles. The first one was a slow process via fatigue-type failure. A cyclic pressure exerted by stationary pulsating bubbles caused the propagation of a crack pre-existing in the primary crystal to a critical length which led to fragmentation. The second mechanism was a sudden process due to the collapse of bubbles in a passing cavitation cloud. The pressure produced upon the collapse of the cloud promoted rapid monotonic crack growth and fast fracture in the primary crystals. The third observed mechanism was normal bending fracture as a result of the high pressure arising from the collapse of a bubble cloud and the crack formation at the branch connection points of dendritic primary crystals. The fragmentation of dendrite branches due to the interaction between two freely moving dendritic primary crystals was also observed. A simplified fracture analysis of the observed phenomena was performed. The specific fragmentation mechanism for the primary crystals depended on their morphology and mechanical properties.	Apr 2017
I13-2-Diamond Manchester Imaging	Synchrotron quantification of ultrasound cavitation and bubble dynamics in Al–10Cu melts W. W. Xu , I. Tzanakis , P. Srirangam , W. U. Mirihanage , D. G. Eskin , A. J. Bodey , P. D. Lee Ultrasonics Sonochemistry 31, 355 - 361 DOI: 10.1016/j.ultsonch.2016.01.017 Diamond Proposal Number(s): [9082] Show Abstract ▼ Abstract: Knowledge of the kinetics of gas bubble formation and evolution under cavitation conditions in molten alloys is important for the control casting defects such as porosity and dissolved hydrogen. Using in situ synchrotron X-ray radiography, we studied the dynamic behaviour of ultrasonic cavitation gas bubbles in a molten Al–10 wt% Cu alloy. The size distribution, average radius and growth rate of cavitation gas bubbles were quantified under an acoustic intensity of 800 W/cm2 and a maximum acoustic pressure of 4.5 MPa (45 atm). Bubbles exhibited a log-normal size distribution with an average radius of 15.3 ± 0.5 μm. Under applied sonication conditions the growth rate of bubble radius, R(t), followed a power law with a form of R(t) = αtβ, and α = 0.0021 & β = 0.89. The observed tendencies were discussed in relation to bubble growth mechanisms of Al alloy melts.	Jul 2016
I13-2-Diamond Manchester Imaging	In situ observation and analysis of ultrasonic capillary effect in molten aluminium I. Tzanakis , W. W. Xu , D. Eskin , P. D. Lee , N. Kotsovinos Ultrasonics Sonochemistry 27, 72 - 80 DOI: 10.1016/j.ultsonch.2015.04.029 PMID: 26186822 Diamond Proposal Number(s): [9082] Show Abstract ▼ Abstract: An in situ synchrotron radiographic study of a molten Al1- wt% Cu alloy under the influence of an external ultrasonic field was carried out using the Diamond-Manchester Branchline pink X-ray imaging at the Diamond Light Source in UK. A bespoke test rig was used, consisting of an acoustic transducer with a titanium sonotrode coupled with a PID-controlled resistance furnace. An ultrasonic frequency of 30 kHz, with a peak to peak amplitude at 140 microns, was used, producing a pressure output of 16.9 MPa at the radiation surface of the 1-mm diameter sonotrode. This allowed quantification of not only the cavitation bubble formation and collapse, but there was also evidence of the previously hypothesised ultrasonic capillary effect (UCE), providing the first direct observations of this phenomenon in a molten metallic alloy. This was achieved by quantifying the re-filling of a pre-existing groove in the shape of a tube (which acted as a micro-capillary channel) formed by the oxide envelope of the liquid sample. Analytical solutions of the flow suggest that the filling process, which took place in very small timescales, was related to micro-jetting from the collapsing cavitation bubbles. In addition, a secondary mechanism of liquid penetration through the groove, which is related with the density distribution of the oxides inside the groove, and practically to the filtration of aluminium melt from oxides, was revealed. The observation of the almost instantaneous re-filling of a micro-capillary channel with the metallic melt supports the hypothesised sono-capillary effect in technologically important liquids other than water, like metallic alloys with substantially higher surface tension and density.	Nov 2015

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