SKM 2023 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 4: Topical Session: Fundamentals of Fracture – Micromechanical Fracture Experiments
MM 4.4: Topical Talk
Montag, 27. März 2023, 11:45–12:15, SCH A 216
Capturing Micromechanical Crack Tip Stress States and Toughening Plasticity in 2D and 3D — •Thomas E. J. Edwards1, Johannes Ast1,2, Szilvia Kalácska1,3, Xavier Maeder1, Jon Wright4, and Johann Michler1 — 1Empa, Feuerwerkerstrasse 39, 3602 Thun, Switzerland — 2CEA, 17 rue des Martyrs, 38054 Grenoble, France — 3Mines Saint-Etienne, Univ Lyon, CNRS, UMR 5307 LGF, France — 4ESRF, 38000, Grenoble, France
Crack tip toughening mechanisms in metals require plasticity, i.e. slip; the present study sheds predictive light on what local stress states lead to an increased dissipation of mechanical energy through plasticity. It also confirms the notion that the plastic performance of a material cannot be solely interpreted from elastic strain measurements, even if undertaken in-situ, or from post-mortem TEM imaging of dislocation structures. Pre-notched single crystal W microcantilevers were deformed in situ, whilst elastic and total strains at the notch tip were captured correlatively by DIC and HR-EBSD with sub-100 nm resolution. From the basic elastic and total strains and rotations hence measured, as well as post-mortem TEM, the following could be extracted: maps of shear stresses resolved onto individual slip systems, pure plastic strain resolved onto slip axes and GND density - all throughout loading, as well as the total dislocation density of the near-surface layer post-mortem. Further, we demonstrate a novel method to extract the full stress tensor, point-wise in 3D, again with ~100 nm resolution, on micromechanical testpieces under load: nano-beam 3D-XRD computed tomography at ESRF ID11.