Experimental and thermodynamic study of high-temperature phase stability of Fe–Zr binary alloy

This work investigated the high-temperature phase stability of Fe–Zr binary alloy using the CALPHAD approach combined with an experimental study. The controversial Fe23Zr6 phase in the Fe–Zr system was recognized as a stable phase by annealing at 1273 K for 1440 h, followed by X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. The conditions affecting the stability of the Fe23Zr6 phase, such as the cooling rate, annealing time, and atmosphere, were investigated. The experimental results indicated that the Fe23Zr6 phase precipitates more under longer annealing time and faster cooling rate, and the phase is not oxygen stabilized. The liquidus temperature from the Fe2Zr_C15 phase to the Zr end region was measured using high temperature differential scanning calorimetry. A combination of the experimental results and the findings in recent literature enabled us to reoptimize the Fe–Zr system using the CALPHAD approach.