Influence of hydrogen on the elastic properties and dislocation behavior in Fe-Cr and Fe-Ni alloys by DFT calculations.

The effect of interstitial hydrogen on the elastic properties of bcc Fe, bcc Fe-Cr, and bcc Fe-Ni was investigated using density functional theory calculations. Our results indicate that the elastic moduli decrease linearly with increasing hydrogen concentration. The consequences of hydrogen for the mechanical properties of bcc Fe, bcc Fe-Cr, and bcc Fe-Ni were analyzed, considering various factors such as the ideal shear stress, Peierls stress, number of dislocation pile-ups, and critical crack growth lengths. At the same hydrogen concentration, compared to the bcc Fe and bcc Fe-Ni systems, fewer dislocation pile-ups and shorter critical crack growth lengths can facilitate the nucleation and propagation of cracks in the bcc Fe-Cr system. Finally, we propose a mechanism to explain the influence of Cr and Ni on hydrogen embrittlement.