Fundamental Study of Cavitation Melt Processing: Opening the Way to Treating Large Volumes (UltraMelt)

Lead Research Organisation: Brunel University
Department Name: Mech. Engineering, Aerospace & Civil Eng

Abstract

Ultrasonic cavitation treatment offers sustainable, economical and pollution-free solutions to melt processing of conventional and advanced metallic materials with resulting significant improvement of quality and properties. However, the transfer of this advanced and promising technology to industry has been hindered by difficulties in treating large volumes of liquid metal as required by processes such as continuous casting. The time is right to tackle the problem as the industry is looking for new advanced technologies for sustainable manufacturing and our economic competitors, e.g. USA and China, are performing extensive scientific research in this area. The selection of this topic is both appropriate and ambitious. Current knowledge cannot answer a seemingly simple question: how long does it take to treat a certain volume of liquid with an ultrasonic source for minimum energy input, cost and complexity? This research aims to answer this question paving the way to extensive industrial use of ultrasonic melt processing with the benefit of improving the properties of lightweight structural alloys, simultaneously reducing the need for degassing and grain refinement additives - polluting (Cl, F) and expensive (Zr, T, B, Ar) - and eliminating complicated processing steps such as fluxing and rotary degassing. Before technological advances can be made, scientific understanding of the underlying phenomena, causes and effects, is essential. This project aims to respond to the challenge of efficiently treating large liquid volumes by: (1) developing a comprehensive numerical model that couples various multi-scale and multiphysics phenomena occurring inside and outside the cavitation region and by (2) changing emphasis from conventional static batch treatment to processing in continuous liquid flow. The novelty of the suggested approach lies in a fully three-dimensional, quantified experimental characterization and numerical description of (i) the primary and extended cavitation region, (ii) acoustic and secondary flows, (iii) mass-transfer through the boundary of the cavitation region, and (iv) processing in a moving volume (flow). The results of this research open the way to treating large volumes of melt with fewer ultrasonic sources and in a shorter time. To achieve the aims, dedicated, quantifiable experiments with three-dimensional characterization plus the use of responsive indicators of treatment efficiency will be combined with advanced modelling; bridging and coupling different length and time-scales and physical phenomena, ranging from the vibrational growth and collapse of individual cavitation bubbles, to the transport of bubble clusters in the bulk fluid and possible re-entrainment in the intense acoustic zone, and to the mass transfer throughout the treated volume. The influence of collapsing bubbles on flow momentum, energy and turbulence will be included in a fully coupled system. The experimental results will be used both as input and for validation of the model throughout its development.

Planned Impact

Melt treatment is the primary stage of any metal production followed by casting (solidification) of ingots or final shapes. Ultrasonic cavitation treatment offers sustainable, economical and pollution-free solutions to melt processing of conventional and advanced metallic materials with resulting significant improvement of quality and properties. However, the transfer of this advanced and promising technology to industry has been hindered by difficulties in treating large volumes of liquid metal as required by processes such as continuous casting. This project aims at fundamental understanding of phenomena underlying this potentially revolutionary materials processing technology, paving the way to its industrial implementation, and educating specialists in this area.
The results of this project will enable much-awaited industrial application of environmentally friendly ultrasonic melt processing to degassing and structure modification of advanced light-alloy materials and their composites for modern applications driven by sustainability and environment. The ultrasonic melt processing will result in reduction or elimination of cleaning gases (green-house gases, Cl, and F) and expensive cleaning and grain-refining additions (Ar, Zr, Ti, and B) while allowing the production of high-quality light-weight materials, not only from primary but also from recycled stock. This will additionally increase sustainability of light-weight materials. For example, the replacement of primary aluminium with recycled materials will have the immediate effect of decreasing by 95% energy consumption and reducing by 0.3 tonne/per tonne Al CO2-equivalent emissions typically spent on the primary electrolytic reduction and refining of aluminium.
Furthermore, the developed new knowledge and models can be used for the development of light-metal composite materials and applied to other physical means of melt processing (e.g. electro-magnetic vibrations), which is outside the scope of the current project. In addition, the knowledge obtained and models can be used in other research and industrial fields where cavitation is induced in a physico-chemical system. Examples of such systems can be found in pharmaceutical, biotechnological, chemical, and food industries.
The results of the research will be actively disseminated in the academic and technological communities through international and national conferences and seminars; publications in peer-reviewed journals; and through existing academic and industrial networks of the applying research centres. The results can be directly exploited by R&D centres and industry for the up-scaling of laboratory results to the industrial processing of light alloy melts (degassing, casting); and the models and fundamental knowledge developed can be used for the advances in new technologies in metallurgical and other industries. The results will be of interest for both the academic community (sonochemistry, acoustics, physical chemistry, materials science, hydraulics) and the industry (metal production, chemical and food industry).
All in all (as illustrated above) the cavitation-aided melt processing technologies enabled by the fundamental knowledge, numerical models and up-scaling methodology gained in this project will contribute to the improvement of the quality of life through environmental sustainability, reduced green-house effect, and the development of new products, and also strengthen the international competitiveness of UK industry.
Key beneficiaries include the two young researchers educated and experienced in this project, and producers of aluminium alloys (Alcoa, Rio-Tinto-Alcan, Novelis), master alloys (Foseco, LSM), automobiles (JLR, Vauxhall), and airspace technique (Airbus-EADS, ESA).

Publications

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Tzanakis, I. (2014) Advanced calibration of a high-temperature cavitometer in 2014 Meeting of European Society of Sonochemistry (ESS), France

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Lebon G (2016) A model of cavitation for the treatment of a moving liquid metal volume in International Journal of Cast Metals Research

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Lebon G (2015) Application of the "Full Cavitation Model" to the fundamental study of cavitation in liquid metal processing in IOP Conference Series: Materials Science and Engineering

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Tzanakis I (2016) Fundamental studies on cavitation melt processing in IOP Conference Series: Materials Science and Engineering

 
Description New experimental tools have been developed and tested that allow us to measure the acoustic pressure and cavitation intensity in liquids including Al melt as well as observe the cavitation and related flow patterns on macroscopic (particles image velocimetry and high speed imaging in water) and microscopic (synchrotron radiation through liquid Al). New models have been developed to link microscopic cavitation phenomena to macroscopic liquid flow. Computer simulation results have been validated on a water model and liquid aluminium.
Exploitation Route The recommendations are made for further upscaling of the ultrasonic melt processing technology (laboratory-scale trials have been performed). The developed experimental and numerical tools can be used for cavitation research beyond the scope of the current project. A new project proposal is under development to bring the research to the next level (computer simulations and industrial trials).
Sectors Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Transport

 
Description The project is finished. The findings are used for publications and presentations. Experimental results are used for model validation. The developed tools will help to upscale environmentally friendly and economically efficient technology. Based on the findings and expertise obtained we are trying to reach out to other fields of science and technology, e.g. fuels. food, medicine, through new collaborations and project proposals. One project proposal has been submitted in 2016 and another is planned in 2017. We also had an internal impact acceleration project within Brunel University London aimed at using the results of the project for improving the quality of automotive casting alloys.
First Year Of Impact 2016
Sector Aerospace, Defence and Marine,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Transport
Impact Types Economic

 
Description EPSRC standard proposal
Amount £1,215,681 (GBP)
Funding ID EP/R011095/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 03/2018 
End 02/2021
 
Description Calibration of cavitometer 
Organisation National Physical Laboratory
Country United Kingdom 
Sector Academic/University 
PI Contribution A unique tool for measuring cavitation activity in liquids, also at high temperatures has been acquired by BCAST and calibrated using advanced facilities of National Physical Laboratory. This collaboration is essential part of the project and has been accounted for in the project budget. Advanced calibration facilities of NPL and expertise of NPL researchers were used ti characterize and calibrate the unique cavitometer that will be further used in experimental part of the project. The outcome of this work will be reported at an international conference and published as a journal paper.
Start Year 2013
 
Description Oxford Brookes 
Organisation Oxford Brookes University
Country United Kingdom 
Sector Academic/University 
PI Contribution With the move of Dr Tzanakis to Oxford Brookes University as a Senior Lecturer, we have established collaboration in applying for further funding, which resulted so far in four project applications with two being sucessful. Brunel university contributes with equipment and expertise.
Collaborator Contribution Oxford Brooeks university contricutes with access to facilities and expertise.
Impact Several journal and conference papers, project proposals
Start Year 2016
 
Description Setting up and upgrading PIV and fast imaging system 
Organisation University of Oxford
Department Centre for the Environment
Country United Kingdom 
Sector Academic/University 
PI Contribution As a part of collaboration with Oxford University, we participated and partially funded the upgrade and setting up of an advanced PIV and fast imaging system that is essential for achieving the objectives of the project. This collaboration is integral part of the project proposal with budget allocated. Ultramelt project partially covered financially the upgrade and setting up of an advanced PIV and fast imaging system in Oxford that will be used for studying cavitation, acoustic streaming and solidification under ultrasonic field.
Start Year 2013