报告题目：On the solidification kinetics of metal alloys: A study using 3-D phase field modeling and synchrotron X-ray image techniques

　　主讲嘉宾：Zhipeng Guo (School of Materials Science and Engineering, Tsinghua University, Beijing, China)

　　时　　间：8月23日（周二）上午10:00—12:00

　　地　　点：李薰楼 249 会议室

　　报告摘要：

　　To reveal the underlying physics during solidification of metal alloys requires development of powerful and effective methodology, including both experimental and modeling approaches. The advancement of the 3rd generation synchrotron X-ray image techniques enables us to observe phase transitions during solidification of metallic alloys in situ, which greatly alter our traditional viewpoint concerning the basic solidification behaviors including dendrite growth, crystal orientation selection, and coarsening. Besides, the state-of-art phase field model is becoming more popular nowadays to simulate such microstructure transition during solidification. Currently, a great deal of effort has been focused on further development of these two powerful tools and accordingly my research attention has been focused on:

　　 (1) Development of a 3-D phase field model to simulate the microstructure transition during solidification of metal alloys. In particular, an algorithm, namely Para-AMR, comprising of adaptive mesh refinement (AMR) and parallel (Para-) computing capabilities was developed to solve the phase field equations. Numerical tests results revealed that this algorithm could improve the computational efficiency for about three orders of magnitude, greatly shortening the computation time for solving the phase field equations.

　　(2) In situ observing the microstructure transition in response to the external forces (electromagnetic fields, ultrasound and mechanical stirring) using synchrotron X-ray. Both radiography and tomography were applied to reveal the full physics of the solidification phenomena in real space and time scales, and to fully testify the validity of the phase field modeling results.

　　Accordingly, important solidification behaviors, including dendrite growth (for both aluminum alloy and magnesium alloy), fragmentation, and coarsening were studied, compared with either experiment results or existing theories, and new physics were revealed.

　　报告人简介：

　　郭志鹏博士：助理教授，清华大学，现在访问学者，卢瑟福阿普尔顿国家实验室，英国，博士后，牛津大学，材料系，博士，清华大学，机械工程系，在等国际著名学术期刊发表论文余篇，多次在国际学术会议上获得最佳展板奖。主要从事研究领域：（）航空发动机涡轮盘新型材料、微观组织及成形工艺研究；（）金属材料成形过程宏、微观结构演化的多尺度模拟和表征；（）高强度射线、纳米或中子射线实验装置开发以及合金相变过程微观组织的原位观察等。目前负责承担的项目主要有商发材料专项，总装预研项目，清华大学自主青年项目，公司国国际合作项目，英国皇家学会资助项目和国家自然科学基金青年基金等等。

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