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.