Multi-stage evolution mechanism of precipitate phases at twin boundaries in Inconel 617 superalloy during long-term aging

Abstract

This study provides a comprehensive analysis of the mechanical properties and microstructural evolution of Inconel 617 superalloy during long-term aging at 760 °C, aiming to elucidate the multi-stage evolution mechanism of the γ' phase at twin boundaries and M₂₃C₆ carbide interfaces. The findings indicate that twins predominantly form during solution annealing, while M₂₃C₆ carbides are preferentially precipitated at twin boundaries, followed by the ordered nucleation of the γ' phase at the twin boundary/M₂₃C₆ interface, resulting in the formation of a unique twin boundary/M₂₃C₆/γ' composite microstructure. The γ' phase at this interface undergoes a multi-stage evolution, encompassing disordered atomic aggregation, ordered precipitation, coarsening, and dissolution, ultimately reaching a stable state. Selective atomic diffusion is crucial in this process, with Cr and Mo preferentially diffusing toward twin boundaries to facilitate M₂₃C₆ carbide precipitation, while Al and Ti gradually promote γ' phase formation at the twin boundary/M₂₃C₆ interface. Furthermore, the multi-stage evolution of the γ' phase, driven by interdiffusion, effectively suppresses the coarsening of M₂₃C₆ carbides at twin boundaries. The synergistic evolution and mutual inhibition between M₂₃C₆ carbides and the γ' phase at twin boundaries are critical to maintaining the long-term thermal-mechanical stability of the alloy. This multi-stage evolution mechanism underscores the importance of tailoring precipitation behavior to optimize the long-term mechanical properties of Inconel 617 superalloy.