SKM 2023 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 33: Topical Session: Fundamentals of Fracture – Amorphous Metals

MM 33.1: Talk

Wednesday, March 29, 2023, 15:45–16:00, SCH A 215

In situ measurement of plasticity accompanying Hydrogen induced cracking — Leonel Stermann, Loïc Vanel, and •Döme Tanguy — Institut Lumière Matière, UMR5306 Université Lyon 1 - CNRS, Université de Lyon 69622 Villeurbanne cedex, France

Single crack propagation is studied in a Hydrogen embrittled aluminum alloy. Hydrogen is introduced in the system by electrochemical reactions in an acid aqueous medium. After Hydrogen charging, tensile tests are performed in air, on notched samples, with a micro-tensile machine. An optical microscope is used to follow single crack initiation and propagation at a high magnification. Digital Image Correlation gives the displacement field on the surface with a spatial resolution of about 1 micron. It enables the determination of the position of the crack tip and the local velocity at a sub-grain scale. The equivalent Von Mises strain is calculated and gives a precise measure of the local plastic field which accompanies crack propagation. In addition to the primary plasticity which is emitted from the crack tip or its immediate neighborhood in the form of two intense slip bands,It is systematically found a secondary plastic zone which spreads over several microns ahead of the tip. The characteristics of the plastic zone are measured, together with the velocity and the applied stress intensity factor. In addition, different fracture mechanisms are found on the fracture surface. In particular there are transitions in the fracture mode from intergranular smooth to transgranular parallel to the grain boundary plane. The local fracture mechanisms, in the vicinity of the surface, are linked to the local velocities and plastic deformations.