Computer modelling of hydrogen embrittlement in an industrial alloy

S. SIMONETTI, G. BRIZUELA, A. JUAN

Varsovia

Conferencia; The 23rd General Conference of the Condensed Matter Division of the European Physical Society, CMD23; 2010

European Physical Society

The interaction between four-hydrogen atoms in an FCC FeNi alloy zone having a vacancy (V) was studied using the atom superposition and electron delocalization molecular orbital (ASED-MO) method. The sequential absorption is a favourable process, for such absorption the total energy difference is always negative. The positions of lower energy result to be those close to the vacancy (V) (see Fig. 1). The minimum Fe–H distances lay between 1.623 Å and 1.689 Å of its first neighbour Fe while the H-vacancy distances are between 1.22 Å - 1.30 Å. The energy agglomeration studies show that for a number of H atoms equal or higher than 3, the hydrogen prefers to be alone instead of agglomerating.Then, VH1 and VH2 are the major complexes. For H, there is a possible competition between the formation of another VH1 pair and the formation of a VH2 triplet (the energies are similar). Under normal conditions, the vacancy concentration in the material is smaller than the H atom concentration and a large proportion of the vacancies may be associated to one or two H atoms.