The in-situ observation of dislocations interacting with micro-structural features during mechanical loading in metallic materials has led to unprecedented insights into deformation mechanisms. Evolution of the dislocation sub-structure under deformation determines the plastic behavior of the material, such as the response to severe loading. The microstructural complexity of engineered metallic materials, for instance as encountered in multiphasic superalloys, makes the identification of dislocation mechanisms and their microstructural interactions challenging to characterize,thereby precluding defect-level predictions of failure and performance degradation. High spatial and temporal resolution are required to experimentally observe dislocations and their dynamics during loading.
In the present work, we report a novel in-situ deformation apparatus integrated in an SEM with transmission imaging capabilities, providing sharp dislocation contrast amenable to the dislocation interactions governing plastic localization in metals. The dynamics and character of dislocations that move near, or interact with microstructure are explored using location-specific in-situ TSEM tensile experiments. d-ration [21,22].
Lift-out by Focus Ion Beam for sample preparation
Transfer/Thinning on Push-to-Pull for In-situ TSEM experiment
F. Wang, G.H. Balbus, Y. Su, S. Xu, J. Shin, P.F. Rottmann, J.C. Stinville, L.H. Mills, O.N. Senkov, I.J. Beyerlein, T.M. Pollock, D.S. Gianola. Multiplicity of Dislocation Pathways in a Refractory Multi-Principal Element Alloy. Science, 2020.
J.C. Stinville, E.R. Yao, P.G. Callahan, J. Shin, F. Wang, M.P.Echlin, T.M. Pollock, D.S. Gianola. Dislocation Dynamics in a Nickel-Based Superalloy Via In-Situ Transmission Scanning Electron Microscopy. Acta Materialia, 2019.
P.G. Callahan, J.C. Stinville, E.R. Yao, M.P. Echlin, M.S. Titus, D.S. Gianola, M. De Graef, T.M. Pollock. Transmission Scanning Electron Microscopy: Defect Observations and Image Simulations. Ultramicroscopy, 2018.