Effect of hydrogen on electronic structure of fcc iron in relation to hydrogen embrittlement of austenitic steels

Abstract

The total structural energy per primitive lattice cell, density of electron states, spatial distribution of electrons and elastic modulus in fcc Fe–H solid solutions are studied using the density functional theory and Wien2k program package. It is shown that hydrogen increases the density of electron states at the Fermi level. The density of conduction electrons is increased in the vicinity of hydrogen atoms, which suggests that the latter migrate over the crystal lattice surrounded by the clouds of conduction electrons. Calculations of elastic modulus show that hydrogen decreases the shear modulus c44. The consequences for mechanical properties of hydrogen‐charged austenitic steels are analysed taking into account the stress for activation of dislocation sources, the line tension of dislocations and the distance between dislocations in pile‐ups. It is concluded that hydrogen‐induced brittleness of austenitic steels can be satisfactorily interpreted in terms of the hydrogen effect on the electronic structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The effect of absorbed hydrogen on the dissolution of steel

“…The presence of a single H interstitial can therefore influence the bonding of at least 40 Fe atoms (octahedral H interstitial), and at least 38 Fe atoms (tetrahedral H interstitial), overall resulting in the weakening of the Fe bond strength. The weakening of Fe—Fe bonds due to the presence of interstitial H within the Fe lattice has been shown in several similar models in the literature [45, 60, 61, 62, 63, 64, 65, 66]. When H is present at an interstitial position within the Fe lattice an electron transfer of around 0.35 e − to 0.6 e − takes place from the Fe atom to the neighbouring H atom [45, 60, 66], which is well in the range of our estimation.…”

“…8). H atoms diffuse through the Fe lattice during cathodic charging surrounded by clouds of conducting electrons [62].…”

Discrete dislocation plasticity HELPs understand hydrogen effects in bcc materials

“…Even for fcc metals, the concentration used in Birnbaum and Sofronis (1994) is too high. This implies that the hydrogen elastic shielding mechanism, while being viable, might not be the dominant factor in HELP phenomena, as noted by other researchers (Teus et al, 2007;Taketomi et al, 2008;Gavriljuk et al, 2010) and will be revisited in this paper.…”

Carbon, Nitrogen and Hydrogen in Iron-Based Solid Solutions: Similarities and Differences in their Effect on Structure and Properties

“…Ab initio calculations of the electronic structure in the f.c.c. iron containing carbon, nitrogen or hydrogen, as studied in [7][8][9], have shown that carbon decreases density of electron states at the Fermi level of f.c.c. iron, whereas nitrogen and hydrogen increase it (Fig.…”