On the activation energy of the σ-phase formation in a pure and Ti-doped Fe–Cr alloy

The σ-phase formation in Fe53.8Cr46.2 and Fe53.8Cr46.2-0.3at%Ti by isothermal annealing in the temperature interval of 923–1003 K was investigated in situ by 57Fe Mössbauer spectroscopy. The process of transformation was succesfully analyzed using the Johnson–Avrami–Mehl equation, and it was quantitatively described in terms of the activation energy, E which was determined by several methods. The best-value of E as average of all data was found to be equal to 196±2 kJ/mol for the Fe–Cr sample and to 153±2 kJ/mol for that doped with Ti.