Experimental determination of the Ni–Ni₅Zr eutectic point for binary Ni–Zr alloy phase diagram

The Ni–Ni₅Zr eutectic alloy becomes a promising structural material owing to its high strength and desirable plasticity. However, those nominal eutectic alloys with previously assumed compositions of Ni-8.8 at.% Zr and Ni-9.0 at.% Zr were found to involve a considerable amount of primary (Ni) phase. Hereby, an experimental study was conducted by differential scanning calorimetry and careful electron microscopy to clarify the situation. A total of 13 alloys in the composition range of 8.8 ~ 11.0 at.% Zr were explored with respect to their phase transition temperatures and microstructure evolution characteristics. The Ni-9.9 at.% Zr alloy exhibited primary (Ni) phase, whereas the Ni-10.1 at.% Zr alloy displayed primary Ni₅Zr phase. Finally, the eutectic point was determined as Ni-10.0 at.% Zr alloy with a transition temperature of 1467 K, and the relevant part of Ni–Zr phase diagram was revised accordingly.