Molecular dynamics study of the hydrogen and carbon effect on mobility of grain boundaries in α-iron

Abstract

The effect of hydrogen and carbon on the mobility of a grain boundary in the α-iron is studied by means of molecular dynamics. The calculations are performed within the linear elasticity approach. Both hydrogen and carbon atoms reveal a strong tendency to grain boundary segregation. As shown, the hydrogen atoms, located in the vicinity of the grain boundaries, decrease the activation enthalpy of grain boundary migration, which results in their higher mobility in comparison with the hydrogen-free case. In contrast, the carbon atoms strongly pin the grain boundary at its initial position within the whole range of temperatures and also under the strain used in the modelling. The obtained results are interpreted based on the opposite effect of the studied interstitial elements on the atomic interactions: the increase in the concentration of free electrons due to hydrogen and its decrease due to carbon. As supposed, the hydrogen-caused increase of grain boundaries mobility can be a reason for the early start of recrystallization, as it is observed in the hydrogen-charged iron-based alloys.