Thermodynamic assessment of the Fe–Ni–Rh–Ti system

Construction of accurate phase diagram database could be a prerequisite to the accelerated optimization of critical engineering materials, which is especially true in the innovation of Ni-based alloys. In this work, to examine the role of Rh addition on the phase relations in Ni-based alloys, we have reassessed the binary Rh–Ti, the ternary Fe–Rh–Ti, Fe–Ni–Ti and Ni–Rh–Ti systems using the CALPHAD (CALculation of PHAse Diagrams) approach associated with the first-principles calculations. Based on a critical review of all the available experimental phase diagrams and thermodynamic data, a self-consistent thermodynamic database of the Fe–Ni–Rh–Ti system has been successfully established by extrapolating the descriptions of the accepted binary and ternary systems. The present results show that the addition of Rh could improve the thermal stability of the FCC_L12 phase, and in particular, an incorporation of 5 at.% Rh could give rise to an increase of ∼40 °C in the FCC_L12-to-FCC_A1 transition temperature in the Ni–Fe–Ti alloys. Thus, the thermodynamic database established in this work is expected to guide future development of Rh-containing Ni-based alloys.