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ME Seminar - Two tier compatibility conditions for phase transforming polycrystals

Event and Seminar

  • Date

    02 Feb 2023

  • Organiser

    Department of Mechanical Engineering, PolyU

  • Time

    16:00 - 17:00

  • Venue

    N103, PolyU Campus Map  


e-Certificate of attendance will be provided. Latecomer or early leaver of the seminar might NOT be eligible for an attendance certificate.

Guest Speaker: CHEN Xian, Sherry

Associate Professor, Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology

Prof. Chen received her Ph.D. and M.S. in Solid Mechanics from the Department of Aerospace Engineering and Mechanics, University of Minnesota, United States. Afterwards, she worked at Lawrence Berkeley National Lab as the ALS Postdoctoral Fellow. She was working at the Department of Mechanical and Civil Engineering, Caltech from 2015 to 2016 as a Visiting Faculty. After joining HKUST, Prof. Chen received the Early Career Award for the GRF grant and continuously awarded 6 GRF grants. She was awarded the Simon Fellowship by Isaac Newton Institute, Cambridge, UK in 2019 for her contribution to the design of complex materials. The research of Prof Chen’s group integrates the theories of mechanics of crystalline solids with advanced structural characterization methods and algorithms to develop new phase-transforming materials having desirable properties. She developed in situ nanomechanics experiments and theoretical approaches for phase transforming polycrystals with much enhanced fatigue resistance. These materials have emerging applications in medical devices, and energy conversion devices.


For micro and nano-devices used for biomedical applications, e.g. neural stents and heart valves, both crystallographic compatibility and grain boundary engineering play profound role in their functionalities. But these two mechanisms are not well synergized. Here we theorize a two-tier compatibility criterion to optimize the textures across the grain boundary, to enhance the mechanical reversibility of transforming polycrystals under stress-induced phase transformation. In this talk, I will present an experimental demonstration that a micropillar fabricated at the grain boundary achieves a remarkable transformability under the demanding driving stress (~600MPa) over 10,000 nanomechanical cycles without fulfilling the crystallographic compatibility condition by lattice parameters. The experiment provides an important insight to the design of low fatigue materials by considering the orientation dependent compatibility between grains. By modern nanotechnologies, it is possible to fabricate bi-crystal, tri-crystal and/or quart-crystal nano structures with designed textures, which underlies a new method for the smart materials and structures design.

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