Thermodynamic properties and lattice misfit of Ir-based superalloys

► Composition change has more contribution to lattice misfit than thermal expansion. ► Ir/Ir3Ti and Ir/Ir3Nb are coherent interfaces with constrained lattice misfit. ► Ir/Ir3Zr and Ir/Ir3Hf are semi-coherent interfaces with unconstrained lattice misfit. ► Rafting ability based on lattice and elastic misfits is proposed for the first time.