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

Abstract

AbstractThe 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)