Study of high temperature phase stability and phase transformation kinetics of sigma and parent alpha phase in Fe55Cr45 (wt. %) alloy

This study presents an extensive experimental characterization of high temperature phase stability and phase transformation kinetics of intermetallic sigma and alpha phases of Fe55Cr45 alloy carried out by dynamic calorimetry. Sigma phase was synthesized from its parent alpha phase of Fe55Cr45 alloy by annealing at 973 K for 360 h in vacuum. A comparative thermal study of sigma and alpha phase alloy was performed from 373 to 1400 K by Differential Scanning Calorimeter. Single inflection of ferro to para magnetic transition (T-c) was observed in DSC upto melting at 831 K for alpha phase. For sigma phase, the sigma to alpha decomposition temperature was measured as 1122 K. It was observed that sigma phase decomposition temperature is nearly 30 K higher than the presently reported 1093 K. Kinetics study of sigma to alpha phase transformation has been carried out by employing various heating rates from 1 to 50 K min(-1) in DSC. The non isothermal KJMA model has been adopted to model the fraction transformed to determine the order and kinetics parameters. The activation energy for sigma to alpha phase transformation was obtained 240-260 kJ mol(-1) by employing KJMA model. (C) 2017 Elsevier B.V. All rights reserved.