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Ultrasonic Cavitation Treatment of Metallic Alloys
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Ultrasonic Cavitation Treatment of Metallic Alloys

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: closed (31 October 2019) | Viewed by 17106

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Iakovos Tzanakis

E-Mail Website1 Website2
Guest Editor
Department of Engineering, Computing and Mathematics, Oxford Brookes University, Oxford, UK
Interests: ultrasonic processing; ultrasonic melt treatment; cavitation; bubble dynamics; shock waves
Prof. Dr. Dmitry Eskin

E-Mail Website
Guest Editor
Brunel Centre for Advanced Solidification Technology, Brunel University London, Uxbridge, UK
Interests: solidification procesing of light alloys; casting defects; ultrasonic processing; advanced characterisation of cavitation; alloy development; phase transformations; micro-structural evolution in light alloys

Special Issue Information

Dear Colleagues,

The current trend in solidification research is developing a generic, energy-efficient, economical, sustainable, and pollution-free technology that can be applied to different alloy systems. Ultrasonic-cavitation melt treatment (UST) is a rather universal technology that can be applied to conventional and advanced metallic materials, regardless of their composition, while being environmentally friendly, cost effective, and ready to be implemented in conventional casting technologies such as direct-chill, continuous, or shape casting, as well as in emerging technologies of additive manufacturing and nanocomposite materials.

The beneficial effects of UST, such as assisted nucleation, activation of substrates (wetting), deagglomeration and fragmentation of solid phases, degassing of the melt, and grain refinement of the as-cast product, stems from the growth, collapse, and implosion of cavitation bubbles as a result of alternate flactuations in ultrasonic pressure. Although successfully demonstrated on the laboratory and pilot scale, UST has not yet found widespread industrial implemetation. This is mostly due to the lack of in-depth understanding of the fundamental mechanisms behind the improved metal quality and structure refinement. Additionally, the temperature requirements and opacity of the metals have imposed strict limitations on the study of cavitation bubble dynamics and cavitation activity within liquid metals.

Thus, this Special Issue aims to scrutinise the use of UST in technology of high-quality metallic alloys with improved mechanical properties, and to assess the driving mechanisms of cavitation-induced effects, such as grain refinement, degassing, wetting, and particle distribution. In this context, the research published in this Issue will consider the interaction between cavitation field and acoustic streaming with the melt flow and the suspended solid/liquid phases, the characterization and mapping of cavitation activity in a melt volume, and the possibility of achieving a high efficiency in processing large melt volumes through technological approaches for the commercial implementation of ultrasonic processing technology.

It is our pleasure to invite you to submit a manuscript for this Special Issue. Full experimental or numerical papers, communications, and reviews are all welcome.

Dr. Iakovos Tzanakis
Prof. Dr. Dmitry Eskin
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • ultrasonic melt treatment
  • metallic alloy
  • composite
  • degassing
  • solidification
  • in situ characterisation
  • acoustic pressure
  • acoustic streaming
  • heterogeneous nucleation
  • structure refinement
  • fragmentation
  • intermetallics
  • sono-capilary effect

Published Papers (6 papers)

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Research

12 pages, 2498 KiB  
Article
Characterization of Ultrasonic Bubble Clouds in A Liquid Metal by Synchrotron X-ray High Speed Imaging and Statistical Analysis
by Chuangnan Wang, Thomas Connolley, Iakovos Tzanakis, Dmitry Eskin and Jiawei Mi
Materials 2020, 13(1), 44; https://doi.org/10.3390/ma13010044 - 20 Dec 2019
Cited by 9 | Viewed by 2847
Abstract
Quantitative understanding of the interactions of ultrasonic waves with liquid and solidifying metals is essential for developing optimal processing strategies for ultrasound processing of metal alloys in the solidification processes. In this research, we used the synchrotron X-ray high-speed imaging facility at Beamline [...] Read more.
Quantitative understanding of the interactions of ultrasonic waves with liquid and solidifying metals is essential for developing optimal processing strategies for ultrasound processing of metal alloys in the solidification processes. In this research, we used the synchrotron X-ray high-speed imaging facility at Beamline I12 of the Diamond Light Source, UK to study the dynamics of ultrasonic bubbles in a liquid Sn-30wt%Cu alloy. A new method based on the X-ray attenuation for a white X-ray beam was developed to extract quantitative information about the bubble clouds in the chaotic and quasi-static cavitation regions. Statistical analyses were made on the bubble size distribution, and velocity distribution. Such rich statistical data provide more quantitative information about the characteristics of ultrasonic bubble clouds and cavitation in opaque, high-temperature liquid metals. Full article
(This article belongs to the Special Issue Ultrasonic Cavitation Treatment of Metallic Alloys)
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13 pages, 6528 KiB  
Article
Contactless Ultrasonic Cavitation in Alloy Melts
by Koulis Pericleous, Valdis Bojarevics, Georgi Djambazov, Agnieszka Dybalska, William D. Griffiths and Catherine Tonry
Materials 2019, 12(21), 3610; https://doi.org/10.3390/ma12213610 - 3 Nov 2019
Cited by 12 | Viewed by 3008
Abstract
A high frequency tuned electromagnetic induction coil is used to induce ultrasonic pressure waves leading to cavitation in alloy melts. This presents an alternative ‘contactless’ approach to conventional immersed probe techniques. The method can potentially offer the same benefits of traditional [...] Read more.
A high frequency tuned electromagnetic induction coil is used to induce ultrasonic pressure waves leading to cavitation in alloy melts. This presents an alternative ‘contactless’ approach to conventional immersed probe techniques. The method can potentially offer the same benefits of traditional ultrasonic treatment (UST) such as degassing, microstructure refinement and dispersion of particles, but avoids melt contamination due to probe erosion prevalent in immersed sonotrodes, and it can be used on higher temperature and reactive alloys. An added benefit is that the induction stirring produced by the coil, enables a larger melt treatment volume. Model simulations of the process are conducted using purpose-built software, coupling flow, heat transfer, sound and electromagnetic fields. Modelling results are compared against experiments carried out in a prototype installation. Results indicate strong melt stirring and evidence of cavitation accompanying acoustic resonance. Up to 63% of grain refinement was obtained in commercial purity (CP-Al) aluminium and a further 46% in CP-Al with added Al–5Ti–1B grain refiner. Full article
(This article belongs to the Special Issue Ultrasonic Cavitation Treatment of Metallic Alloys)
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16 pages, 4366 KiB  
Article
Role of Acoustic Streaming in Formation of Unsteady Flow in Billet Sump during Ultrasonic DC Casting of Aluminum Alloys
by Sergey Komarov and Takuya Yamamoto
Materials 2019, 12(21), 3532; https://doi.org/10.3390/ma12213532 - 28 Oct 2019
Cited by 12 | Viewed by 2357
Abstract
The present work investigated melt flow pattern and temperature distribution in the sump of aluminum billets produced in a hot-top equipped direct chilling (DC) caster conventionally and with ultrasonic irradiation. The main emphasis was placed on clarifying the effects of acoustic streaming and [...] Read more.
The present work investigated melt flow pattern and temperature distribution in the sump of aluminum billets produced in a hot-top equipped direct chilling (DC) caster conventionally and with ultrasonic irradiation. The main emphasis was placed on clarifying the effects of acoustic streaming and hot-top unit type. Acoustic streaming characteristics were investigated first by using the earlier developed numerical model and water model experiments. Then, the acoustic streaming model was applied to develop a numerical code capable of simulating unsteady flow phenomena in the sump during the DC casting process. The results revealed that the introduction of ultrasonic vibrations into the melt in the hot-top unit had little or no effect on the temperature distribution and sump profile, but had a considerable effect on the melt flow pattern in the sump. Our results showed that ultrasound irradiation makes the flow velocity faster and produces a lot of relatively small eddies in the sump bulk and near the mushy zone. The latter causes frequently repeated thinning of the mushy zone layer. The numerical predictions were verified against measurements performed on a pilot DC caster producing 203 mm billets of Al-17%Si alloy. The verification revealed approximately the same sump depth and shape as those in the numerical simulations, and confirms the frequent and large fluctuations of the melt temperature during ultrasound irradiation. However, the measured temperature distribution in the sump significantly differed from that predicted numerically. This suggests that the present mathematical model should be further improved, particularly in terms of more accurate descriptions of boundary conditions and mushy zone characteristics. Full article
(This article belongs to the Special Issue Ultrasonic Cavitation Treatment of Metallic Alloys)
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13 pages, 3526 KiB  
Article
Numerical Modelling of the Ultrasonic Treatment of Aluminium Melts: An Overview of Recent Advances
by Bruno Lebon, Iakovos Tzanakis, Koulis Pericleous and Dmitry Eskin
Materials 2019, 12(19), 3262; https://doi.org/10.3390/ma12193262 - 6 Oct 2019
Cited by 12 | Viewed by 2951
Abstract
The prediction of the acoustic pressure field and associated streaming is of paramount importance to ultrasonic melt processing. Hence, the last decade has witnessed the emergence of various numerical models for predicting acoustic pressures and velocity fields in liquid metals subject to ultrasonic [...] Read more.
The prediction of the acoustic pressure field and associated streaming is of paramount importance to ultrasonic melt processing. Hence, the last decade has witnessed the emergence of various numerical models for predicting acoustic pressures and velocity fields in liquid metals subject to ultrasonic excitation at large amplitudes. This paper summarizes recent research, arguably the state of the art, and suggests best practice guidelines in acoustic cavitation modelling as applied to aluminium melts. We also present the remaining challenges that are to be addressed to pave the way for a reliable and complete working numerical package that can assist in scaling up this promising technology. Full article
(This article belongs to the Special Issue Ultrasonic Cavitation Treatment of Metallic Alloys)
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31 pages, 8101 KiB  
Article
Ultrasonic Processing for Structure Refinement: An Overview of Mechanisms and Application of the Interdependence Theory
by Nagasivamuni Balasubramani, David StJohn, Matthew Dargusch and Gui Wang
Materials 2019, 12(19), 3187; https://doi.org/10.3390/ma12193187 - 28 Sep 2019
Cited by 15 | Viewed by 2947
Abstract
Research on ultrasonic treatment (UST) of aluminium, magnesium and zinc undertaken by the authors and their collaborators was stimulated by renewed interest internationally in this technology and the establishment of the ExoMet program of which The University of Queensland (UQ) was a partner. [...] Read more.
Research on ultrasonic treatment (UST) of aluminium, magnesium and zinc undertaken by the authors and their collaborators was stimulated by renewed interest internationally in this technology and the establishment of the ExoMet program of which The University of Queensland (UQ) was a partner. The direction for our research was driven by a desire to understand the UST parameters that need to be controlled to achieve a fine equiaxed grain structure throughout a casting. Previous work highlighted that increasing the growth restriction factor Q can lead to significant refinement when UST is applied. We extended this approach to using the Interdependence model as a framework for identifying some of the factors (e.g., solute and temperature gradient) that could be optimised in order to achieve the best refinement from UST for a range of alloy compositions. This work confirmed established knowledge on the benefits of both liquid-only treatment and the additional refinement when UST is applied during the nucleation stage of solidification. The importance of acoustic streaming, treatment time and settling of grains were revealed as critical factors in achieving a fully equiaxed structure. The Interdependence model also explained the limit to refinement obtained when nanoparticle composites are treated. This overview presents the key results and mechanisms arising from our research and considers directions for future research. Full article
(This article belongs to the Special Issue Ultrasonic Cavitation Treatment of Metallic Alloys)
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13 pages, 4467 KiB  
Article
Effects of Ultrasonic Introduced by L-Shaped Ceramic Sonotrodes on Microstructure and Macro-Segregation of 15t AA2219 Aluminum Alloy Ingot
by Tao Zeng and YaJun Zhou
Materials 2019, 12(19), 3162; https://doi.org/10.3390/ma12193162 - 27 Sep 2019
Cited by 7 | Viewed by 2034
Abstract
The effects of ultrasonic introduced by L-shaped sonotrodes made of high-temperature-resistant ceramic on the microstructure and macro-segregation of solidifying 15t AA2219 aluminum alloy ingots have been examined in the present study. The macroscopic morphology of the corrosion of the sonotrode has been observed. [...] Read more.
The effects of ultrasonic introduced by L-shaped sonotrodes made of high-temperature-resistant ceramic on the microstructure and macro-segregation of solidifying 15t AA2219 aluminum alloy ingots have been examined in the present study. The macroscopic morphology of the corrosion of the sonotrode has been observed. Grain refinement has been observed, the shape and size of the precipitated phase of the ingot were counted, and the degree of segregation along the transverse direction at 500 mm from the head of the ingot has been evaluated. The results reveal that the L-shaped ceramic ultrasonic introduction device can effectively avoid the erosion of high-temperature melt on the sonotrode and the heat radiation of the high-temperature heat flow to the transducer. Furthermore, the scanning electron microscope (SEM) and chemical composition detection results also indicate that the inter-dendritic micro-segregation of the equiaxed grains can be reduced, and the macro-segregation of the chemical composition of the ingot can be suppressed, and more homogeneous microstructures can be obtained when ultrasonic has been applied during solidification. Full article
(This article belongs to the Special Issue Ultrasonic Cavitation Treatment of Metallic Alloys)
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