Experimental study of the phase equilibria of the Ni-Zr system

The eutectic reaction between the NiZr and NiZr₂ compounds in the Ni-Zr binary phase diagram was evaluated according to the previous experimental measurements and thermodynamic calculations. A discrepancy between the calculations and the measurements exists. In order to determine definitely this eutectic temperature, Ni-Zr alloys of the compositions 65, 68, 72 and 74 wt.% Zr were prepared by melting in an arc furnace under a purified argon atmosphere. The phase transformation temperature was measured by Differential Scanning Calorimetry using both alumina and zirconia crucibles. At heating rates of 5, 10 and 20 K min^-1, the eutectic temperature between the NiZr and NiZr₂ compounds was determined consistently to be 1022 ± 5°C. Zirconia crucibles can be used in Differential Scanning Calorimetry measurements of zirconium-containing alloys but only below 1170°C.