Strain rate and hydrogen effects on crack growth from a notch in a Fe-high-Mn steel containing 1.1 wt% solute carbon

• Published in: International journal of hydrogen energy Vol. 45; no. 1; pp. 1125 - 1139
• Main Authors: Najam, Hina, Koyama, Motomichi, Bal, Burak, Akiyama, Eiji, Tsuzaki, Kaneaki
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-01-2020
• Subjects: Crack propagation; Dynamic strain aging; High-Mn steel; Hydrogen embrittlement; Intergranular crack; High-Mn steel; Intergranular crack; Hydrogen embrittlement; Crack propagation; Dynamic strain aging
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2019.10.227

Effects of strain rate and hydrogen on crack propagation from a notch were investigated using a Fe-33Mn-1.1C steel by tension tests conducted at a cross head displacement speeds of 10−2 and 10−4 mm/s. Decreasing cross head displacement speed reduced the elongation by promoting intergranular crack initiation at the notch tip, whereas the crack propagation path was unaffected by the strain rate. Intergranular cracking in the studied steel was mainly caused by plasticity-driven mechanism of dynamic strain aging (DSA) and plasticity-driven damage along grain boundaries. With the introduction of hydrogen, decrease in yield strength due to cracking at the notch tip before yielding as well as reduction in elongation were observed. Coexistence of several hydrogen embrittlement mechanisms, such as hydrogen enhanced decohesion (HEDE) and hydrogen enhanced localized plasticity (HELP) were observed at and further away from the notch tip resulting in hydrogen assisted intergranular fracture and cracking which was the key reason behind the ductility reduction.
•Effects of strain rate and hydrogen on crack propagation from a notch are studied.•Yield strength and elongation are degraded by hydrogen charging.•Early crack initiation at the notch tip before apparent yielding is observed.•Coexistence of several hydrogen embrittlement mechanisms are observed.