First-principles Study of Hydrogen-induced Embrittlement in Fe Grain Boundary with Cr Segregation

Abstract

First-principles tensile tests were performed to investigate the effect of Cr segregation on the hydrogeninduced embrittlement in Fe grain boundaries. The Fe grain boundary with H and Cr segregation exhibited the higher maximum stress and strain to failure than those of the Fe grain boundary with only H segregation. Cr segregation suppressed the extension of the Fe-Fe bond weakened by H segregation. In the Fe grain boundary with H and Cr segregation, the decrease in the charge density in the bond with straining was suppressed because of charge transfer from the Cr atom to its neighboring Fe atoms. This charge accumulation in the grain boundary region is responsible for the reinforcement of bonds in the Fe grain boundary with H segregation, contributing to the suppression the hydrogen-induced embrittlement of Fe grain boundaries.

Ab Initio Study of the Combined Effects of Alloying Elements and H on Grain Boundary Cohesion in Ferritic Steels

“…For instance, grain boundaries (GBs) are likely trapping sites for H [3,4] but are also prone to suffer from hydrogen enhanced decohesion (HEDE) [5]. Both the segregation tendency of H to grain boundaries and the effect of H on GB cohesion can be influenced by alloying elements [6,7]. In the study at hand, we investigate the co-segregation of H and typical alloying elements in ferritic steels, C, V, Cr, and Mn to shed some light on their combined effects on grain boundary embrittlement.…”

“…Cr has been studied in α-Fe and reported to segregate to and enhance grain boundary cohesion of Σ 5(210) and Σ 3(111) GBs [12,13]. The co-segregation of Cr and H was investigated in the Σ 3(111) GB, where Cr was found to deter the segregation of H and suppress the H-induced embrittlement [7,14]. In γ-Fe, Cr is cohesion enhancing at the Σ 11(113)[110] GB, due to strengthening chemical effects [15,16].…”

On the role of vacancy-hydrogen complexes on dislocation nucleation and propagation in metals

“…As hydrogen has an affinity to get trapped at several defect sites in the microstructure like grain boundaries, voids, triple junctions, phase boundaries, crack tips, interstitial and substitutional sites. For a better comprehension, a great deal of effort in simulations, specifically, molecular dynamics [20][21][22][23][24] and first principle methods [25][26][27] are done to provide atomistic insights into HE mechanisms. These simulations provide hydrogen interaction with grain boundaries, crack tip events, surface energy, generalized stacking fault energy (GSFE) and lattice slip.…”

Hydrogen-enhanced intergranular failure of sulfur-doped nickel grain boundary: In situ electrochemical micro-cantilever bending vs. DFT

“…One of the prominent examples is the simulation of HEDE of GB in Ni [9,[26][27][28][29], which has shown that atomic H tended to segregate to the Ni GB and demonstrated the GB embrittling effect. Moreover, the synergistic effect between segregated impurities has drawn attention to the investigation of solute co-segregation at GBs, such as H-carbide co-segregation [30,31], H-Cr co-segregation in α-Fe GB [32,33], C-O co-segregation in α-Ti GB [34], C, B, O, Fe, and Hf co-segregation in Mo GB [35], or H-C and H-Mo co-segregation in Ni GB [29]. Although S is known to segregate to Ni GBs and decrease GB cohesion [10,[36][37][38][39], the H-S interaction and its co-segregation effect as well as the kinetics of H-S segregation in Ni GB have not been studied sufficiently at the atomic level.…”