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-transformation (T-HR-T) and temperature-time transformation (T-T-T) diagrams were obtained for crystallization processes. A knowledge of the kinetic model governing crystallization is not needed because both transformation curves can be obtained from non-isothermal calorimetric experiments. The calorimetric study was performed by means of differential scanning calorimetry. The method was applied to analyse crystallization processes of Fe-Ni-based amorphous alloys prepared by melt spinning. The compositions studied were Fe₄₀Ni₄₀P₁₄Si₆, Fe₄₀Ni₄₀P₁₀Si₁₀ and Fc₄₀Ni₄₀P₆Si₁₄. A good concordance was oberved between the experimental T-HR-T curves obtained by calculation and the experimental data, which verifies the reliability of the method. In the T-T-T diagrams, the agreement was good in process Bl, while in processes Al and Cl there are small differences that could be related to different crystallization products obtained in isothermal/non-isothermal experiments.