Intergranular strain localization patterns in extremely anisotropic polycrystalline aggregates of Magnesium”


Monday, April 8, 2019 - 3:30pm


Elings 1605


Dr. Can Aydiner

Dr. C. Can Aydıner is an Associate Professor of Mechanical Engineering and the co -director of the Mechanics ofAdvanced Materials Laboratory at Bogazici University, Istanbul, Turkey. He is also currently a Visiting Associate in Mechanical and Civil Engineering Department at California Institute of Technology and a Fulbright Visiting Scholar. Dr. Aydıner’s chief interest is in experimental investigations of polycrystalline aggregates that can capture the deformation physics at various microstructural length scales. The current drive for models that can represent microstructural strain fields— and not just their average— is clearly necessary for tailoring microstructure for function and non-empirical characterization of material failure. Such models require spatially-resolved data for calibration and, more fundamentally, the determination of their operating length-scale. To this end, Dr. Aydıner has been utilizing a heavily automated implementation of digital image correlation with optical microscopy that focuses on in situ experimentation, large statistics and cyclic loading paths. Dr. Aydıner has also investigated complex polycrystalline aggregates with the complementary advanced diffraction techniques, particularly during his previous tenure as a Director’s postdoctoral fellow at Los Alamos National Laboratory. Dr. Aydıner holds M.S. and Ph. D. degrees from California Institute of Technology in Applied Mechanics and a B.S. degree in Mechanical Engineering from Middle Technical University, Turkey.
Magnesium alloys are the lightest structural metals, but their structural application is hampered by the complexity of their crystallite-scale deformation that operates with multiple slip and twin mechanisms. They are hence prime candidates to benefit from advanced polycrystalline models and an extensive literature formed to address their anisotropic and load-path-dependent behavior. While these attempts typically seek validity in an aggregate-average sense, there is also a recent drive towards higher-fidelity modeling that can represent strain fields at some microstructural length scale. In this talk, we present data that can counterpart such models, detailing the intergranular strain localization signature of wrought Magnesium AZ31 polycrystals. The method is area-scanning digital image correlation with optical microscopy and the focus will be on the sharp rolling texture. In one sense of the load, the material exhibits profuse twin propagation, and we detail the multi-scale nature of the tensile-twin-driven band formation. In the reverse load where twin activity is subdued, the material presents another interesting network of strain localization, rooted in dynamic recrystallization events in the previous rolling process. With the two dominant localization superstructures identified in each sense of the load, we finally present how they interact over a fully-reversed strain cycle.

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