Please use this identifier to cite or link to this item: http://buratest.brunel.ac.uk/handle/2438/10951
Title: In situ observation and analysis of ultrasonic capillary effect in molten aluminium
Authors: Tzanakis, I
Xu, WW
Eskin, DG
Lee, PD
Kotsovinos, N
Keywords: Cavitation;Liquid metal;Melt-filtration;Micro jet;Oxide;Sono-capillary
Issue Date: 2015
Publisher: Elsevier
Citation: Ultrasonics Sonochemistry, 27: 72 - 80, (2015)
Abstract: An in situ synchrotron radiographic study of a molten Al-10 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.
URI: http://www.sciencedirect.com/science/article/pii/S1350417715001224
http://bura.brunel.ac.uk/handle/2438/10951
DOI: http://dx.doi.org/10.1016/j.ultsonch.2015.04.029
ISSN: 1350-4177
1873-2828
Appears in Collections:Brunel Centre for Advanced Solidification Technology (BCAST)

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