Morphology evolution of Ir–Nb–X (X = Hf, Ta, or Ti) ternary alloys

Abstract

The microstructure evolution of nine samples from three Ir-base ternary systems, Ir–Nb–Hf, Ir–Nb–Ta, and Ir–Nb–Ti, was investigated by microstructure observation using scanning electron microscopy (SEM), composition map-analysis using electron probe microscopy analysis (EPMA), and phase determination using X-ray diffraction (XRD) patterns. The fcc/L1 2 two-phase structure was detected in all the samples. Lattice misfits between fcc and L1 2 phases were calculated. Ir–Nb–Ta and Ir–Nb–Ti alloys exhibited a microstructure quite similar to that of Ni-base superalloys, and the cuboidal L1 2 precipitates in Ir–Nb–Ta and Ir–Nb–Ti alloys could maintain up to 1900 °C.