Experimental study on the eutectic temperature between NiZr and NiZr₂ compounds

Considering the discrepancy between the thermodynamic calculations and the experimental measurements from literature, the eutectic temperature between NiZr and NiZr₂ compounds was determined experimentally in the present work. Ni-Zr alloys with the composition of 65wt%, 68wt%, 72wt% and 74wt% Zr, located between NiZr and NiZr₂, were prepared by melting in an arc furnace under a purified argon atmosphere. Using both commercial alumina and self-made zirconia crucibles, the phase transformation temperature was measured at different heating rates by differential scanning calorimetry (DSC), and the temperature was determined to be 1022±5°C. In the mean while, the reactions between the experimental alloys and the crucibles were predicted thermodynamically, which confirmed the applicability of the alumina crucibles under the experimental temperature (<1100°C). Zirconia has an allotropic transformation from monoclinic to tetragonal type at 1170°C, below which the zirconia crucibles can be used in the measurements of phase equilibria and thermodynamics for zirconium-containing alloys.