Understanding the effect of hydrogen trapping on dislocation-nanoprecipitate interactions: A molecular dynamics study

A molecular dynamics-based modeling framework is invoked to understand the influence of trapped hydrogen on dislocation-precipitate interactions. The hydrogen trapped at the copper (Cu) precipitate-iron (Fe) matrix interface increases the critical resolved shear stress (CRSS) for dislocation movement. The CRSS for dislocation movement across precipitates depends on the nature of the interface, precipitate size, dislocation line lengths, and hydrogen concentration. The CRSS for dislocation movements for materials with larger precipitates, shorter dislocations, incoherent precipitate-matrix interfaces, and more hydrogen is generally higher. The mechanism associated with the movement of a dislocation across the precipitate depends on the dislocation line lengths. There is a transition from a simple cutting-through mechanism for shorter dislocations to a combination of dislocation cutting-through and climbing for longer dislocations. The hydrogen sensitivity index is higher for materials with more trapped hydrogen, coherent precipitate-matrix interfaces, and shorter dislocations. This study suggests Cu could reduce steel's hydrogen susceptibility by altering the dynamics of dislocation interactions with Cu precipitates.