Effect of alloying additions on the hydrogen-induced grain boundary embrittlement in iron.

Using ab initio density functional theory calculations, we have investigated the influence of Mo, V and Pd on the H-induced grain boundary embrittlement in Fe. We find that, in the high impurity concentration systems, all of the three alloying elements facilitate H embrittlement at the Σ3 (111) [Formula: see text] grain boundary in Fe. The calculated binary effects of the H-X (X = Mo, V, Pd) couples are 0.063, 0.074 and 0.040 eV, respectively. On the other hand, in the large unit cell with low impurity concentration, both Mo and V can facilitate H embrittlement, and the binary effects of pairs are 0.152 and 0.164 eV, respectively. While Pd reduces the H embrittlement on the cohesion of the Fe grain boundary with the binary effect of - 0.1 eV. The H-X (X = Mo, V, Pd) interactions are interpreted by electronic structure analyses.