Time-Temperature-Transformation from metastable to equilibrium structure in Fe-Ga

A huge difference between the structure and the properties of equilibrium and metastable Fe-Ga alloys along with an uncertain specification for their metastable state lead to an urgent necessity to understand the cooling rate role in the formation of the alloys’ structure. We studied the structure of Fe-27%Ga alloy after cooling, in situ during cooling with different cooling rates and after isothermal annealing up to 300 h between 300 and 575 °C to report the alloy structure and present, for the first time, the Time-Temperature-Transformation (TTT) diagram for the metastable bcc to equilibrium fcc transition in this alloy. The critical cooling rates are determined as the beginning and the end of the formation of equilibrium L12 phase.