THE EFFECT OF CARBON ON THE ELECTRONIC STRUCTURE OF FeNi ALLOYS CONTAINING A STACKING FAULT

G. GONZÁLEZ; P. V. JASEN; E. A. GONZALEZ; L. MORO; A. JUAN

New Developments on Metallurgy and Applications of High Strength Steels

TMS (LONDON)

Año: 2008; p. 1207 - 1213

Fe-Ni alloys are widely used in high temperature applications. Under appropriate operative conditions the accumulation of carbon at microvoids, grain boundaries and defects produce an important loss of its mechanical resistance. In the present work, we have studied the interaction of carbon with FCC Fe-Ni alloy in a 1:1 ratio containing a stacking fault (SF). As model of the alloy, we used a 182 atoms supercell forming a seven layer slab of (111) compact planes. The normal stacking sequence, ABCABC was changed to ABABC. We used two calculation methods widely known in materials science simulations, the first a tight binding approach and the second the VASP (Vienna Ab Initio Simulation package) which is a Density Functional Theory method. The calculations were performed at the central zone of the cell finding the optimum geometry for the carbon atom. We used the concept of Density of States (DOS) to study the electronic structure and the Crystal Orbital Overlap Population (COOP) for bonding analysis. The zone close to the SF becomes an accumulation zone. The metal-metal bonding is dramatically reduced when carbon is included while a strong Ni-C and Fe-C bond is developed.