The behaviour of hydrogen in high-strength steels plays a key role in the long-term stability and mechanical properties of such materials. Structural defects within the material, such as grain boundaries, dislocations, nanovoids and phase boundaries between the matrix and precipitates present in the material, play the most critical role in the phenomenon of hydrogen embrittlement.
Atomistic simulations are a critical component in understanding the influence of hydrogen in material systems. However, due to the large system sizes required to simulate, for example, low-symmetry grain boundaries or misfit dislocation between the host matrix and inclusions, conventional ab initio simulations are neither reliable nor feasible. In this direction, we have developed scale-bridging atomistic potentials based on the tight-binding approximation, which allow for a fully quantum-mechanical treatment of the system. Using this approach, we have examined the energetics and kinetics of hydrogen in the vicinity of extended defects in iron-based materials. Particular emphasis has been placed on the influence of H on the cohesion properties of phase boundaries between ferrite and non-metallic inclusions such as TiN, where the role of incoherency is critical.