时　间：2017年10月19日下午15:00

地　点：动力与机械学院学术报告厅

主讲人：刘晓伟 博士

欢迎各位师生踊跃参加！

Abstract

Microstructures dominate the mechanical properties of metallic materials. The traditional Hall-Petch relationship provides people the method to strength materials by reducing grain size but there is much sacrifice of ductility. In recent years, people have developed many different kinds of microstructures to enhance the strength of materials but with inevitable decrease of ductility. During my PhD study and the following Postdoc work, we have fabricated the bimodal structure of nanotwinning induced “hard phase” embedded in the coarse-grain “soft phase” in Cu, which evades the trade-off of strength and ductility. Another advanced microstructure we got is the high-order hierarchical nanotwins (HNTs) that promise great mechanical properties. The fabrication and identifications of the HNTs are reported for the first time, together with the molecular dynamic simulations to describe the spatial distributions of HNTs at atomic scale. Moreover, the in situ TEM characterizes the generation mechanism and conditions for the stable HNTs. In future, there is still great space to optimize the microstructures of materials to further improve the mechanical properties of materials.

Biography

Dr. Xiaowei Liu obtained her PhD degree from the City University of Hong Kong last October. Her research interests include the microstructures and mechanical properties of metallic materials together with the underlying mechanism of the interaction between microstructures and mechanical properties. With the advanced techniques of TEM, SEM and other facilities, she works with both nano materials and bulk materials (such as Cu, Ag, SS 304). Before the study in CityU, Dr. Xiaowei Liu worked in the field of functional materials and theoretical calculations, which mutually promotes her professional training as a researcher.