Investigation on phase relationships and creep properties of Ir–Nb–X (X = Hf, Ta, or Ti) ternary alloys

Previous studies have indicated that Ir–Nb–Zr ternary alloys exhibited better creep properties than Ir–Nb binary alloys. In this work, research on phase relationships and creep properties of Ir–Nb–X (X = Hf, Ta, and Ti) ternary alloys was carried out, from the phase constituent to the creep property. The fcc/L12 two-phase structure was detected in all the alloys. The phase relationship concentrating on the fcc and L12 phases at 2000 °C in the three ternary systems was established. Both fcc and L12 phases formed a continuous solid solution from the Ir–Nb side to the Ir–X (X = Hf, Ta, and Ti) side. The lattice misfit between the fcc and L12 phases was estimated; the Ir–Nb–Hf alloys showed the highest value, while the Ir–Nb–Ti alloys showed the smallest one. The creep properties at high temperature of some alloys were tested. Ir–Nb–Hf exhibited the strongest creep resistance among these three kinds of alloys.