Unveiling γ′ phase creep damage in multi-component Ni-based superalloys by crystal plasticity phase-field simulation

Abstract

A phase-field model combined with crystal plasticity theory is developed to study the precipitation kinetics and creep behavior of multi-component Ni-based superalloys. The quantitative characteristics of the γ′ phase, including its morphology, kinetics, element partitioning, rafting damage and fracture, and plastic strain evolution, are systematically elucidated. Increasing Cr content promotes γ′ precipitation, resulting in a higher volume fraction and smaller particle size. Also, Cr reduces lattice misfit and the effective diffusion coefficient, thereby delaying the γ′ rafting process and reducing plastic strain accumulation. Creep grooves are found at the γ/γ′ interface where dislocations shear γ′ rafts, and the groove-induced stress concentration accelerates the degradation of γ′ rafts. However, the interfacial dissolution of γ′ rafts reduces stress concentration and forms an interfacial transition zone. Additionally, Cr strengthens the γ/γ′ phase interface and elevates the antiphase boundary energy, thus hindering dislocation shearing of γ′ rafts directly or through the antiphase boundary. This work clarifies the effect of Cr on precipitation kinetics and creep behaviour in Ni-based superalloys and reveals the essential interaction mechanisms between stress and γ′ rafts at the γ/γ′ phase interface, providing a valuable reference for composition design and creep failure analysis of high-performance Ni-based superalloys.