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

DOI: 10.1016/j.actamat.2017.10.067 DOI Help

Authors: Bing Wang (University of Hull; University of Cambridge) , Dongyue Tan (University of Hull) , Tung Lik Lee (University of Hull; ISIS Neutron Source) , Jia Chuan Khong (University of Hull; University College London) , Feng Wang (Brunel University London) , Dmitry Eskin (Brunel University London) , Thomas Connolley (Diamond Light Source) , Kamel Fezzaa (Advanced Photon Source) , Jiawei Mi (University of Hull)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acta Materialia

State: Published (Approved)
Published: November 2017
Diamond Proposal Number(s): 8542

Abstract: 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.

Journal Keywords: Ultrafast synchrotron X-ray imaging; Microstructure fragmentation; Microstructure refinement; Solidification; Ultrasound processing

Subject Areas: Engineering, Physics

Instruments: I12-JEEP: Joint Engineering, Environmental and Processing

Other Facilities: Advanced Photon Source