Innovative strategy to optimize the temperature-dependent lattice misfit and coherency of iridium-based γ/γ’ interfaces

Abstract

Ir/Ir3X (X = Hf, Nb, Ta, Ti, V, and Zr) are promising dual-phase materials with high strength at ultrahigh temperatures. However, previous investigations revealed that the relatively large lattice misfit and small critical coherent diameters adversely impact the strength of the Ir/Ir3X interfaces. Herein, a novel strategy is proposed for modeling the ternary alloys by mixing two Ir3X binary alloys having both the negative and positive lattice misfit and to form fully coherent γ/γ’ interfaces with Ir. The ternary Ir3XmVn alloys exhibit good high-temperature performance, such as high bulk modulus (∼200–240 GPa) at 2000 K. Remarkably, the lattice misfit of Ir3XmVn alloys with the Ir matrix (−0.8 %–0%) shows a significant reduction compared to that of the binary Ir3X alloys (−0.6 %–+2.4 %) in the 0–2000 K temperature range. The reduction in lattice misfit is accompanied by an increase in the critical coherent diameters.