Grain boundary alloying segregation to resist hydrogen embrittlement in BCC-Fe steels: Atomistic insights into solute-hydrogen interactions

Grain boundary (GB) segregation of alloying elements is widely recognized to influence the mechanical properties of metallic materials. However, the rational utilization of GBs' chemical heterogeneity to mitigate hydrogen embrittlement (HE) remains challenging. Here, we employ comprehensive first-principles calculations to investigate solute-hydrogen interactions across five distinct GBs. The calculations provide fundamental insights into H concentration, transport, and induced decohesion at BCC-Fe sigma 5 (013)[100] GB with alloying segregations including W, Mo, Nb, and Mn, emphasizing the crucial importance of hydrogen adsorption energies. Through statistically identifying the effective descriptors derived from complex atomic environments of various GBs, we elucidate solute-hydrogen interaction mechanisms at GBs from broadly applicable solute valence and electronegativity factors. The analysis highlights the vital role of concurrently controlling alloying segregation tendency, GB separation work, and local H solubilities, thereby comprehending GB engineering strategies and facilitating design of high-performance alloys with GBs resistant to HE.