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Title: Petr Harcuba: Micro-scale characterization of twinning and dislocation slip in magnesium single crystals by advanced SEM in-situ techniques
Number: 13/22
Status: Closing date exceeded
Begin: Thursday, 07.04. 2022, 14:00
Tutor: Václav Holý, Milan Dopita
Location: Lecture room F2, MFF UK Ke Karlovu 5, first floor

nanocent


Nano Seminar

Thursday, 7.4. 2022, 14.00

Lecture room F2, MFF UK Ke Karlovu 5

Petr Harcuba

Department of Physics of Materials, Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, 121 16, Prague 2

Micro-scale characterization of twinning and dislocation slip in magnesium single crystals by advanced SEM in-situ techniques

Micro-deformation testing has recently gained far-reaching scientific importance as it provides intrinsic information on the dynamics of plastic deformation which is concealed when bulk materials are tested. A combination of in-situ scanning electron microcopy (SEM) during deformation with simultaneous acoustic emission (AE) technique has been employed to study the deformation behavior of single-crystalline Mg micropillars favourably oriented for mechanical twinning and/or dislocation slip. The combination of these two techniques enables the investigation of the underlying physical processes with exceptional spatiotemporal resolution. It is shown that the size-efect stress drops observed are in perfect correlation with the acoustic emission events. AE and subsequent EBSD analysis alow us to distinguish between twinning and dislocation slip. The experimental data were modelled by the finite element method in order to reveal the underlying physical principles of the observed twinning dynamics. It was shown that the thickness of a twin reaches a critical value before the nucleation of another twin is triggered to accommodate further strain. Nucleation and growth are repeated until twins form throughout the whole micropillar. Afterwards, these twins thicken and coalesce until the entire micropillar volume is twinned. In addition, a lineby-line analysis of the scanning electron microscopy images revealed the twin lateral growth rates of the order of 10−5–10−4 m/s.

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