The coarsening behavior of γ′-Ni3(Ti, Al) phase in a precipitation strengthened Fe-based alloy

Abstract

Abstract The γ′-Ni3(Ti, Al) phase is an important strengthening phase of Fe-based alloys and nickel-based superalloys, its coarsening behavior is very important for the strengthening effects. In this study, the precipitation behavior of γ′-Ni3(Ti, Al) phase in a thermally aged precipitation strengthened Fe-based alloy was evaluated during aging at 700\u202f°C and 750\u202f°C for different time using transmission electron microscopy (TEM) and atom probe tomography (APT). The results show that, the homogeneously distributed spherical γ′-Ni3(Ti, Al) particles with L12 structure which coherent with the matrix can be observed in all the aged samples. The size of the precipitate increases, while the number density of the precipitate decreases with aging temperature and time increasing. The volume fraction of γ′ particle is one key factor that influences the strength of bulk sample. During the process of γ′ particle growth, the partition ratios of Ni, Al and Ti between precipitates and matrix decrease with the aging temperature increasing significantly, while increase with aging time prolonging slightly. The Ti/Al ratio decrease with the aging time prolonging and aging temperature decreasing significantly. Based on the experiment results, the coarsening behavior of γ′ phase and their strengthening effects are discussed, which are expected to contribute to the design of Fe-based alloy compositions with improved mechanical properties.