THERMAL-STABILITY STUDY OF FE-NI-BASED ALLOYS - DETERMINATION OF T-HR-T AND T-T-T DIAGRAMS

The low-temperature parts of the temperature-heating rate-transformati on (T-IIR-T) and temperature-time transformation (T-T-T) diagrams were obtained for crystallization processes. A knowledge of the kinetic mo del governing crystallization is not needed because both transformatio n curves can be obtained from non-isothermal calorimetric experiments. The calorimetric study was performed by means of differential scannin g calorimetry. The method was applied to analyse crystallization proce sses of Fe-Ni-based amorphous alloys prepared by melt spinning. The co mpositions studied were Fe40Ni40P14Si6, Fe40Ni40P10Si10 and Fe40Ni40P6 Si14. A good concordance was oberved between the experimental T-HR-T c urves obtained by calculation and the experimental data, which verifie s the reliability of the method. In the T-T-T diagrams, the agreement was good in process B1, while in processes Al and CI there are small d ifferences that could be related to different crystallization products obtained in isothermal/non-isothermal experiments.