EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Hydrogen embrittlement is a fundamental problem in materials science which affects structural materials such as steel. Several mechanisms at the atomic length scale have been proposed, one is hydrogen enhanced decohesion (HEDE), where H accumulates on crystallographic planes and reduces the interplanar cohesion. Grain boundaries could have a significant role in HEDE since they can act as traps for H. To elucidate this mechanism, we carried out first-principles tensile tests, to derive traction-separation laws for cohesive zone models in meso-scale simulations. We present the results of the H effect on the cohesive strength of α-Fe single crystal (001) and (111) cleavage planes, as well as the effect of both, H and C on the Σ5(310)[001] and Σ3(112)[11$\bar{0}$] symmetrical tilt grain boundaries. The calculated results show that the single crystal cleavage planes are much more sensitive to a change in H concentration than the grain boundaries within the studied range of concentrations. We also present the calculation of solution energies of H and C, which allows us to study decohesion for a constant chemical potential of H, and thus for better comparison with experimental results.