报告题目：先进材料凝固过程中同步辐射X射线的实时研究
In-situ study of the solidification of advanced materials using synchrotron X-ray
报告人：Professor Jiawei Mi (米佳伟), Hull University, UK
报告时间：2018年5月22日（星期二）下午3:00
报告地点：国家金属材料近净成形工程技术中心38号楼301会议室
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2018年5月15日
报告人简介：
米佳伟教授目前是英国赫尔大学（Hull University）工程与计算机系教授英国皇家学会（The Royal Society）研究员。在此之前，米教授曾任牛津大学（Oxford University）材料系研究员，伯明翰大学(Birmingham University) 助理研究员，中国北京航空材料研究院轻合金研究室主任，高级研究工程师等职务。米教授及其课题组主要致力于设计和研发先进的金属基高性能结构材料，复合材料和金属玻璃等新材料，以及相关的材料先进制造技术方面的研究。近年来，米教授的团队致力用同步辐射X射线（Synchrotron X-ray）及中子成像及衍射（neutron imaging and diffraction）方法研究材料在三维和四维空间的原子，纳米和微米结构的实时演变过程。特别是在将以上方法应用于超声场和磁场熔体处理和合金凝固控制技术方面一直处于国际领先地位。
米教授从事科研工作以来，已负责或承担30多项各类科研相目，包括英国自然和物理科学研究基金（EPSRC）等；累计科研经费已达近千万英镑。他在材料与工程及自然知名学术期刊上发表论文近120篇，如Acta Mater., Scr. Mater., Sci. Rep., Appl. Phys. Lett., Int. J. Plasticity, Metall. Mater. Trans. A, Mater. Sci. Eng. A, Mater. Design等。米教授主持编辑并撰写的专著“Solidification Processing of Metallic Alloys under External Fields 正在出版过程中。
报告摘要：
In this talk, I give an overview of the recent results from the projects funded by the Royal Society and EPSRC in the past 7 years or so. The focus is about the real-time studies of the growth and fragmentation of dendritic grains and intermetallic phases during the solidification processes under ultrasonic waves and pulse magnetic fields. We have used the specialty beamlines at a number of synchrotron X-ray facilities for the research, including those at the Diamond Light Source, The Advanced Photon Source, the Swiss Light Source, Synchrotron SOLEIL, France, and The European Synchrotron Radiation Facility. The first case is the ultrafast Synchrotron X-ray imaging of the highly dynamic phenomena of ultrasonic bubbles in liquid and semisolid metals including bubble implosion, oscillation and their dynamic interactions with the solidifying phases and liquid-solid metal interface. The ultrafast X-ray images (up to 271,554 fps) revealed, for the first time, the oscillation and implosion of ultrasonic bubbles in liquid and semisolid metal, and how the Zn phases were fractured by the fatigue effect due to the oscillating bubbles.
The second case is the imaging and tomography of the growth and fragmentation of Al3Ni phases in an Al-15%Ni solidified under pulse magnetic field. The time-resolved 3D and 4D datasets showed unambiguously how the Al3Ni phases branched out and grew into dendritic morphologies as the pulse magnetic flux increased and over the threshold value. The research demonstrated that real-time and in-situ visualization of the dynamic microstructural evolution during the solidification processes is absolutely essential for elucidating some of the ambiguities or missing links in the classical theories that were obtained in the past based on the post-mortem microstructural characterization. The challenge ahead and the future trend in this research direction are also briefly discussed.
