Ultrafast synchrotron X-ray imaging studies of microstructure fragmentation in solidification under ultrasound
Ultrafast synchrotron X-ray imaging studies of microstructure fragmentation in solidification under ultrasound
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DOI：
10.1016/j.actamat.2017.10.067
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发表时间：
2018-02-01
期刊：
影响因子：
9.4
通讯作者：
Mi, Jiawei
中科院分区：
文献类型：
--
作者：
Wang, Bing;Tan, Dongyue;Mi, Jiawei
金属合金的超声加工是一种环境友好的绿色液态金属脱气和组织细化技术。然而，由于超声在液态金属和半固态金属中凝固过程中的动态行为难以直接观察，这一领域的许多基本问题仍然没有被完全理解。本文利用美国先进光子源和英国钻石光源所提供的超快同步辐射X射线成像技术(最高可达271,554帧/秒)，系统地研究了超声泡/声流与凝固相之间的动态相互作用。实验结果得到了数值模拟的肯定。首次在原位揭示了液态金属和半固态金属中的混沌气泡内爆和动态气泡振荡。结果表明，超声气泡和增强声流对凝固锌相的破碎和液固界面的破坏作用明显，与理论计算吻合较好。该研究为阐明超声作用下凝固过程中组织破碎和细化的主要机制提供了明确的实验证据和强有力的理论解释。(C)2017 Acta Materialia Inc.，由Elsevier Ltd.出版。
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. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd.