High-Speed Synchrotron X-ray Imaging Studies of the Ultrasound Shockwave and Enhanced Flow during Metal Solidification Processes

Tan, Dongyue; Lee, Tung Lik; Khong, Jia Chuan; Connolley, Thomas; Fezzaa, Kamel; Mi, Jiawei

doi:10.1007/s11661-015-2872-x

Cited by 58 publications

(40 citation statements)

References 36 publications

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“…It is not entirely clear how the fragmentation happens. Very limited direct observations show a mixture of rapid fragmentation from collapsing bubbles, slow separation of fragments assisted by pulsating bubbles and detachment of dendrites from the solidification front assisted by acoustic flow [14,15,16]. Most likely a combination of solute, flow and momentum effects plays role in the fragmentation.…”

Section: Main Mechanisms and Applications Of Ultrasonic Melt Processingmentioning

confidence: 99%

Ultrasonic processing of molten and solidifying aluminium alloys: Overview and outlook

Eskin

2017

Materials Science and Technology

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Abstract. Ultrasonic melt processing attracts a lot of interest both from academic researchers and industry. Despite a long history of the subject, with first accounts dating back to the 1930s, the physics, mechanisms and practical applications are still under development. In the second half of the XXth century, pilot-and industrial scale applications of ultrasonic processing of light alloys were demonstrated for melt degassing, filtration, grain refinement, melt atomisation, and zone refining. In the last 10 years the interest to ultrasonic melt processing grew with regard to understanding the underlying mechanisms of previously established effects, developing numerical models of ultrasonic cavitation and the development of nanocomposite technology. This review paper summarises the mechanisms involved in the ultrasonic melt processing, including cavitation, flows, nucleation, activation, fragmentation and their consequences for degassing, structure refinement and particle dispersion. Some typical mistakes made by researchers in performing experiments and in interpretation of the results are discussed. New advanced methods of studying ultrasonic treatment and phenomena are considered. The paper also gives an outlook to future developments and challenges.

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Section: Main Mechanisms and Applications Of Ultrasonic Melt Processingmentioning

confidence: 99%

Ultrasonic processing of molten and solidifying aluminium alloys: Overview and outlook

Eskin

2017

Materials Science and Technology

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“…One is the inoculation of nucleants via master alloys and through modifying the alloying chemistry . The other is the application of external fields by physical means . One of these is ultrasonic vibration or what will henceforth be called Ultrasonic Treatment (UST).…”

Section: Introductionmentioning

confidence: 99%

“…Both cavitation and acoustic streaming significantly affect grain refinement of the solidifying metal . Cavitation is the phenomenon of the formation, pulsation, growth, and implosion of cavities in the liquid phase and at liquid/solid/gas interfaces kinetically. In liquid metals, cavitation is difficult to model and to simulate on a large size scale due to the requirement to solve the coupled fluid flow and nonlinear cavitation equations in a very small time scale, for example, bubble dynamics time scale is in the range of 10 −20 –10 −8 s. Many efforts have been made to model and simulate cavitation.…”

Section: Introductionmentioning

confidence: 99%

Evolution of the As‐Cast Grain Microstructure of an Ultrasonically Treated Al–2Cu Alloy

et al. 2018

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The evolution of the grain structure of an Al-2Cu alloy is investigated numerically during its solidification while being subjected to ultrasonic treatment. A CAFE (Cellular Automation Finite Element) model coupling fluid flow, heat transfer, nucleation, and grain growth is developed and validated by comparing the results of both numerical simulations and physical experiments. The model successfully describes hydrodynamic fields generated by ultrasonic treatment and their influence on microstructural evolution. This validated model is then used to study the influence of the duration of ultrasonic treatment on temperature distribution and grain structure. A predominantly equiaxed grain structure developed due to the low temperature gradient throughout the melt is a result of the enhanced convection. These results highlight the critical role played by the convection induced by acoustic streaming during casting, that is, facilitating nucleation and grain growth.

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“…Huang et al [20] recently reported measurement of the size distribution of cavitation gas bubbles in an AlCu alloy melt using the synchrotron X-ray radiography whilst the current authors used it to study the ultrasonic capillary effect in a molten metallic alloy [21]. Tan et al [22] observed shockwaves and flows upon cavitation in Bi-based alloys. However, the growth behaviour, number density and underlying mechanisms of cavitation bubble have not been investigated.…”

Section: Introductionmentioning

confidence: 99%

Synchrotron quantification of ultrasound cavitation and bubble dynamics in Al–10Cu melts

Tzanakis

Srirangam

et al. 2016

Ultrasonics Sonochemistry

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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/cm 2 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)=αt β , and α=0.0021 & β=0.89. The observed tendencies were discussed in relation to bubble growth mechanisms of Al alloy melts.

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High-Speed Synchrotron X-ray Imaging Studies of the Ultrasound Shockwave and Enhanced Flow during Metal Solidification Processes

Cited by 58 publications

References 36 publications

Ultrasonic processing of molten and solidifying aluminium alloys: Overview and outlook

Ultrasonic processing of molten and solidifying aluminium alloys: Overview and outlook

Evolution of the As‐Cast Grain Microstructure of an Ultrasonically Treated Al–2Cu Alloy

Synchrotron quantification of ultrasound cavitation and bubble dynamics in Al–10Cu melts

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