Tailoring precipitation‐strengthening in Ir‐based ternary alloys: a first‐principles approach to L1 <sub>2</sub> phase engineering
Xian‐Pei Jiang, Wei Yu, Wei Yan, Haijun Wu, Ji‐Ping Ding, Changyi Hu, Xingjun Liu, Jing Feng, Xiaoyu Chong
Abstract
Abstract Iridium(Ir)‐based superalloys with γ/γ' two‐phase microstructure are recognized as next‐generation high‐temperature materials for aerospace engines operating above 1500 °C. The strengthening phases can markedly enhance the mechanical strength of alloys. However, these phases exhibit significant brittleness, and their properties in Ir‐based alloys remain insufficiently investigated. Here, the high‐throughput calculations were employed to screen the potential γ' phases for Ir 3 X (X = Al, Si, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Pt, Au, Th) through systematic assessment of phase stability, melting points, shear modulus and anti‐phase boundary (APB) energies. Subsequently, lattice misfit was further optimized through third‐element compositional design in Ir 3 (Ti 0.5 X 0.5 ) (X = Nb, Hf, Zr, Ta). The dependence of yield strength on precipitate size was systematically evaluated through the precipitation strengthening effect. Ir 3 (Ti 0.5 Ta 0.5 ) displays a reduced lattice misfit (0.63%), accompanied by a higher shear modulus (207 GPa), elevated APB energy (920 mJ m −2 ), and an increased Poisson’s ratio (0.25), demonstrating a synergistic improvement in these interrelated mechanical characteristics. The increase of density of states value at Fermi level and the right‐shift of the peak in the bonding region result in the improved ductility. The greatest delocalization degree of electrons around Ta and the shorter Ir‐Ta bond lengths are responsible for its higher shear modulus and APB energies. A novel Ir 3 (Ti 0.5 Ta 0.5 ) composition balancing the trade‐off between high strength and ductility is expected to guide the development of Ir‐based superalloys.