Hydrogen in BCC-Iron Alloys: Ab Initio Simulation

Trapping of hydrogen atoms by defects in the crystal lattice of various iron phases is an important factor in the theoretical description of the mechanisms of hydrogen embrittlement in steels. This paper provides a brief overview of our studies of the interaction of hydrogen with point defects and phase boundaries in BCC-iron alloys using ab initio calculations. The capture of hydrogen atoms by alloying impurities, as well as by vacancies (Va) and vacancy complexes VaH_n, grain boundaries (GBs), and the ferrite/cementite interphase boundary, is considered. A hierarchical map of trapping energies associated with common crystal-lattice defects is presented, and the most attractive sites for H traps are identified. The influence of V and Ti alloying impurities on the interaction of H with BCC iron is considered.