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MM: Fachverband Metall- und Materialphysik

MM 19: Topical Session: Hydrogen in Materials: from Storage to Embrittlement II

MM 19.1: Topical Talk

Tuesday, March 19, 2024, 10:15–10:45, C 130

Hydrogen-Induced Fracture Behavior in Cr-Mo Low Alloy Steel: In-situ ETEM Insights on Crack Propagation — •Lin Tian¹, Masanobu Kubota², Petros Sofronis^2,3, Reiner Kirchheim^1,2,4, and Cynthia A. Volkert^1,2,5 — ¹Institute of Materials Physics, University of Göttingen, Göttingen, Germany — ²International Institute for Carbon Neutral Energy Research, Kyushu University, Fukuoka Japan — ³Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, USA — ⁴Max-Planck-Institute for Iron Research, Duesseldorf, Germany — ⁵The International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany

Taking advantage of an in-situ fracture test method inside an environmental transmission electron microscope (ETEM), the fracture behavior of a Cr-Mo low alloy steel is examined. Through controlled gas environments, we compared the fracture behavior of samples in vacuum and in hydrogen gas. In vacuum, the sample fractures by void nucleation and coalescence showing typical ductile fracture behavior. It is found that the ferrite matrix is the major void initiation site due to the low stress triaxiality in the thin sample. However, in the presence of hydrogen gas in the TEM chamber, clear evidence of hydrogen embrittlement is observed. The crack tip in hydrogen gas remains sharp and propagates by the formation and linking up of staircase-shape micro-cracks, without much associated plasticity. We will discuss possible contributions to embrittlement from the effect of hydrogen on (i) dislocation formation and mobility, and (ii) lattice decohesion.

Keywords: Hydrogen embrittlement; Steel; Dislocations; Environmental Transmission Electron Microscopy