STRUCTURE AND PHASE FRACTION OF MELT-SPUN HIGH-CARBON FE-NI-C ALLOYS

The structure and the phase fractions of as-quenched Fe-Ni-C ribbons were studied using Mossbauer spectroscopy, X-ray analysis and SEM. The phase fractions obtained from Mossbauer spectra show presence of the gamma-austenite, Theta, chi and epsilon carbides, a pre-precipitation carbide stage and alpha-martensite. The amount of each phase depends on the chemical composition. An amorphous phase was not found. The possible existence of an hcp iron phase is discussed in connection with the appearence of the pre-precipitation stage of carbides. A comparison of the phase fractions with the phase diagram enabled a model of phase growth during cooling to be proposed. The measurements of microhardness can be explained well by the amount of the phases.