Abstract
Mössbauer effect studies have been done for Fe-1.8 mass%C, Fe-6 mass%Al-2 mass%C, Fe-1.5 mass%Mn-1.8 mass%C, Fe-2.5 mass%Mn-1.8 mass%C and Fe-16 mass%Ni-1.4 mass%C γ-phase (austenite) in order to clarify the distribution of carbon atoms among the octahedral sites of fcc lattice in each alloy. From the obtained fractional intensity of each component of spectra for the Fe-C binary γ-phase, the local interaction energies between the first nearest and second nearest carbon atoms, J1 and J2, were quantitatively determined by means of Monte-Carlo simulation. The values of J1 and J2 were also determined for nitrogen atoms from the previously reported spectra for the Fe-N γ-phase. J1 and J2 were both strongly repulsive for carbon, while for nitrogen, J1 was strongly repulsive but J2 was very weak. From the fractional intensities obtained from the spectra for the ternary alloys, the local interaction energies between carbon and the first nearest or second nearest third element (Al, Mn and Ni), V1 and V2 were determined. V1 for Mn and V2 for Al were strongly attractive. The values of J and V were compared with the data obtained by thermodynamical activity measurements.
