【Academic Lecture】 Antoine GUITTON of Université de Lorraine

           Dr. Antoine Guitton fromUniversité de Lorraine gave an academic lecture in MECE on Sep.3, 2019. In this academic lecture, he initiated the research on the effect of strain path changes in metal plasticity i.e. investigating what happens in metals if the strain occurs in different directions or changes during deformation. His presentation title is: Transmission electron microscopy: a powerful tool to study semiconductors at nanometer scale. AssociateProf. Wenbo Yu hosted this presentation. Prof. Yang Zhou, Prof. Zhengying Huang, Prof. Cuiwei Liu and other teaching faculties attended this lecture as well as graduate students from relevant majors.

        In the aim of following the fast evolution of the industrial demands, developing innovative techniques that allow to understand and to predict the mechanical properties of materials has become a necessity for the Materials Science community. For instance, mechanical tests combined with microstructural investigations provide engineers with the necessary information to computationally predict the mechanical performance of components. Such experiments allow capturing footprints of the deformation mechanisms responsible for the changing microstructure [1,2].

        The Transmission Electron Microscope (TEM) is one of the most well-known techniques for observing and characterizing dislocations in electron transparent thin foils (thickness of ? 100 nm with a useful field of view of few ?m² only) [3,4,5]. Comprehensive dislocation studies at microscopic scale bring valuable information for extrapolating to the macroscopic mechanical response of materials and they can feed numerical advanced multiscale crystal plasticity models [6]. However, fundamental questions on the representativeness of observed phenomenon must be raised when extrapolating discussions to a millimeter-size specimen.

        In this framework, he had successfully combined macroscopic mechanical testing of bulk specimen with a dislocation-scale characterization technique: the Accurate Electron Channeling Contrast Imaging (A-ECCI) [7,8]. A-ECCI is a non-destructive procedure offering the ability to provide, inside a Scanning Electron Microscope (SEM), TEM-like diffraction contrast imaging of sub-surface defects (at a depth of about one hundred of nanometers) on centimetric bulk specimen with still unsurpassed resolutions[9,10]. Firstly, fundaments on the defect contrasts and the experiment procedure will be presented. Secondly the full potentiality of A-ECCI for following the evolution of deformation microstructures will be highlighted in the case of a TiAl based alloy and a ?-metastable Ti [11,12]. Finally, we talked about his presentation and future collaborations.  

References

[1] – A. Guitton, S. Van Petegem, C. Tromas, A. Joulain, H. Van Swygenhoven, L. Thilly, App. Phys. Lett. 24, (2014).

[2] – S. Van Petegem, A. Guitton, M. Dupraz, A. Bollhalder, K. Sofinowski, M.V. Upadhyay, H. Van Swygenhoven, L. Thilly, Exp. Mecha. 57, (2017).

[3] – G.P. Bei, A. Guitton, A. Joulain, V. Brunet, S. Dubois, L. Thilly, C. Tromas, Philos. Mag. 93, (2013).

[4] – A. Guitton, A. Joulain, L. Thilly, C. Tromas, Philos. Mag. 92, (2012).

[5] – A. Guitton, A. Joulain, L. Thilly, C. Tromas, Sci. Rep. 4, (2014).

[6] – K. Gourriet, P. Carrez, P. Cordier, A. Guitton, A. Joulain, L. Thilly, C. Tromas, Philos. Mag. 95, (2015).

[7] – H. Mansour, J. Guyon, M.A. Crimp, N. Gey, B. Beausir, N. Maloufi, Scripta. Mater. 84-85, (2014).

[8] – J. Guyon, H. Mansour, N. Gey, M.A. Crimp, S. Chalal, N. Maloufi, Ultramicroscopy 149, (2015).

[9] – H. Kriaa, A. Guitton, N. Maloufi, Sci. Rep. 7, (2017).

[10] – H. Kriaa, A. Guitton, N. Maloufi, Materials 12, (2019).

[11] – A. Guitton, H. Kriaa, N. Maloufi, Materials 11, (2018).

[12] – M. Ben Haj Slama, N. Maloufi, J. Guyon, S. Bahi, L. Weiss, A. Guitton, Materials 12, (2019).