Atomic interactions and hydrogen-induced γ * phase in fcc iron-nickel alloys

Abstract

Energy of metal-metal (Me-Me) and metal-hydrogen (Me-H) bonds in hydrogen-free and hydrogen-charged fcc iron, nickel, and iron-nickel alloys are ab initio calculated. It is shown that short-range decomposition of Fe-Ni solid solution and difference in Fe-H and Ni-H bonds are responsible for splitting of g reflections in the X-ray diffraction patterns, which is at variance with the common interpretation in terms of a hydrogen-caused γ * phase. X-ray diffraction measurements confirm the absence of miscibility gap in the FeNi-H solid solution and its occurrence in Ni-H. Results of calculations are consistent with the absence of H-H pairs in pure nickel. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.