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Title: Ultrafast synchrotron X-ray imaging studies of microstructure fragmentation in solidification under ultrasound

Ultrasound processing of metal alloys is an environmental friendly and promising green technology for liquid metal degassing and microstructural refinement. However many fundamental issues in this field are still not fully understood, because of the difficulties in direct observation of the dynamic behaviours caused by ultrasound inside liquid metal and semisolid metals during the solidification processes. In this paper, we report a systematic study using the ultrafast synchrotron X-ray imaging (up to 271,554 frame per second) technique available at the Advanced Photon Source, USA and Diamond Light Source, UK to investigate the dynamic interactions between the ultrasonic bubbles/acoustic flow and the solidifying phases in a Bi-8%Zn alloy. The experimental results were complimented by numerical modelling. The chaotic bubble implosion and dynamic bubble oscillations were revealed in-situ for the first time in liquid metal and semisolid metal. The fragmentation of the solidifying Zn phases and breaking up of the liquid-solid interface by ultrasonic bubbles and enhanced acoustic flow were clearly demonstrated and agreed very well with the theoretical calculations. The research provides unambiguous experimental evidence and robust theoretical interpretation in elucidating the dominant mechanisms of microstructure fragmentation and refinement in solidification under ultrasound.
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [5] ;  [6] ;  [7] ; ORCiD logo [2]
  1. Univ. of Hull (United Kingdom). School of Engineering & Computer Science; Univ. of Cambridge (United Kingdom). Dept. of Engineering
  2. Univ. of Hull (United Kingdom). School of Engineering & Computer Science
  3. Univ. of Hull (United Kingdom). School of Engineering & Computer Science; Rutherford Appleton Lab., Didcot (United Kingdom). ISIS Neutron Source
  4. Univ. of Hull (United Kingdom). School of Engineering & Computer Science; Univ. College London (United Kingdom). Dept. of Medical Physics and Biomedical Engineering
  5. Brunel Univ. London (United Kingdom). Brunel Centre for Advanced Solidification Technology
  6. Diamond Light Source Ltd., Didcot (United Kingdom)
  7. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source
Publication Date:
Grant/Contract Number:
AC02-06CH11357; EP/L019965/1; EP/L019884/1; EP/L019825/1
Published Article
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 144; Journal ID: ISSN 1359-6454
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Hull (United Kingdom); Brunel Univ. London (United Kingdom)
Sponsoring Org:
USDOE Office of Science (SC); Engineering and Physical Sciences Research Council (EPSRC); Royal Society (United Kingdom)
Country of Publication:
United States
36 MATERIALS SCIENCE; ultrafast synchrotron X-ray imaging; ultrasonic bubble implosion & oscillation; microstructure fragmentation & refinement; solidification; ultrasound processing
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1437372