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报告人：悉尼大学 安祥海 博士
报告题目：Improving cyclic deformation responses of nanostructured metallic materials via tuning the stacking fault energy and microstructures
Abstract： With respect to the perspective engineering applications of nanostructured (NS) metallic materials, apart from the strength and ductility under monotonic loading, their cyclic deformation response is another essentially crucial concern owning to safety issues. Compared with their CG references, NS materials generally exhibit enhanced high-cycle fatigue (HCF) and decreased low-cycle fatigue (LCF) properties in the light of the dependence of fatigue lives on the stress and strain amplitudes, respectively. Our recent investigations revealed that prominent improvement of the LCF lives and HCF strengths, especially fatigue endurance limits, of NS metals and alloys, can be simultaneously achieved with decreasing their stacking fault energy (SFE). These upgraded fatigue performances with lowering the SFE in NS materials can be attributed not only to the simultaneous increase of their monotonic strength and ductility in macroscale, but also to the crucially decreased cyclic softening behavior in terms of grain coarsening and shear banding in microscale. In addition, the dominant fatigue damage micro-mechanism was also transformed inherently from extensive grain boundary (GB) migration to other local GB activities such as atom shuffling or GB sliding/rotation with the reduction of the SFE. Owing to the limitation of their intrinsic fatigue mechanisms, the fatigue endurance limits of NS metals and alloys cannot always acquire appreciable improvement with their monotonic strengths. However, tuning the microstructures to harvest recrystallized nanostructures can significantly enhance the fatigue strength of NS materials despite the lower tensile strength. These results enable us to timely exploit the knowledge of fatigue behavior of NS metallic materials, which is important both scientifically, for the in-depth comprehension of their deformation behavior, and technologically, for assessing their service utilities in safety-critical structural components, and also open up promising venues for materials design to possess optimal mechanical properties.
Brief Bio： Xianghai An received his PhD degree in Materials Fatigue and Fracture Division, Shenyang National Laboratory for Materials Sciences, Institute of Metal Research, Chinese Academy of Sciences. After receiving PhD degree, he joined the School of Aerospace, Mechatronic and Mechanical Engineering at The University of Sydney as a research fellow, then DVCR research fellow supported by University and is currently a DECRA fellow supported by Australia ARC. He was also conferred on the Alexander von Humboldt Fellowship by Humboldt Foundation in Germany.
Dr. Xianghai An’s research mainly focuses on understanding the microstructures, deformation mechanisms, and mechanical behavior of advanced metallic materials by recourse to extensive microscopy characterization and mechanical testing. Up to date, more than 40 papers with citation and h-index of 990 and 18 (Google Scholar), respectively, have been published in top journals including Nano letters, Acta Materialia, Scripta Materialia, and Applied Physics Letters.