Experimental Study of the Subsolidus Region of the Ir-Ni Phase Diagram

The phase diagram of the refractory Ir-Ni system was reinvestigated in the temperature range of 500-900 °C using a special approach designed to reduce kinetic difficulties in reaching the equilibrium state. Ir-Ni porous nanoalloys obtained by reductive thermolysis at 600 °C of specially prepared multicomponent precursors were used as initial samples in the study of phase equilibria. The thermolysis conditions of the precursors were selected based on thermal analysis data. The formation of Ir-Ni nanoalloys was studied in situ by high-temperature x-ray diffraction on a synchrotron radiation source. The study of samples subjected to long-term annealing at temperatures of 500, 700 and 900 °C confirmed that Ir-Ni alloys formed a continuous series of disordered substitution solid solutions. The existence of Ir₃Ni, IrNi, IrNi₃ intermetallic phases mentioned earlier by other authors was not confirmed. It was experimentally shown that Ir-Ni alloys formed only a continuous series of disordered substitutional solid solutions over the entire composition range in the subsolidus region.