On accelerated design, and characterization of a hydrogen-embrittlement tolerant Mn-Steel

Abstract

Abstract

High-throughput screening based on CALPHAD (CALculation of Phase Diagram) was employed to investigate potential chemical compositions within the Fe-C-Mn alloy system for the hydrogen resistance application. The primary objective was to identify a range of compositions that would exhibit a stable FCC phase while simultaneously expanding the austenitization temperature window. Processing the high-throughput CALPHAD screening led to the composition Fe-1.1C-18.72Mn-6Al-5.01Cr-1.05Si-0.03Cu. Stacking fault energy (SFE) was calculated for this alloy using a thermodynamic model, and the result indicated a relatively high SFE of 66 mJ·m−2, which suggests high stability of the austenite matrix. The designed alloy displays a yield strength (YS) of 426 ± 4 MPa, an ultimate tensile strength (UTS) of 830 ± 10 MPa, and an elongation of 85 ± 2 %. After subjecting the material to hydrogen gas charging, a small elongation loss (around 7.69 ± 1.9 %) was observed, attributable to the hydrogen embrittlement effect. Notably, the dominant mechanism of hydrogen embrittlement was suggested as a plasticity driven mechanism such as Hydrogen-Enhanced Localized Plasticity (HELP) or Hydrogen-Enhanced Strain-Induced Vacancy (HESIV). the high density of void formation near the fracture point of the charged sample and the observation of dimples in the fracture surface provided compelling evidence for this possible embrittlement mechanisms, however more investigations are needed to confirm the dominant mechanism.