A unified physical model for precipitation strengthening in Nickel-Based superalloys

A novel physically unified precipitation strengthening model is established by studying the actual physical process of dislocation pairs shearing γ′ precipitates with different radii on the dislocation slip plane. This model achieves a continuous transition among the classical weak-coupling, strong-coupling, and Orowan models. Classical and modified precipitation strengthening models often overlook certain force interactions during the dislocation slip process, leading to the discontinuity between the weak and strong coupling regimes. Additionally, the physically unified model distinguishes between the two-dimensional (2D) and three-dimensional (3D) radii of γ′ precipitates and incorporates statistical considerations for the range of 2D γ′ precipitate radii sheared by dislocation pairs, thereby improving the accuracy of stress prediction in precipitation strengthening models. The model is validated using the powder metallurgy nickel-based superalloy FGH96 by examining the microstructure and mechanical properties over a wide range of cooling rates to obtain different volume fractions and γ′ precipitate sizes. Experimental results demonstrate that the physically unified model accurately predicts the critical shear stress for different volume fractions and γ′ precipitate sizes, confirming its validity. This model effectively eliminates the limitations of classical models and provides significant insights into the precipitation strengthening mechanism of dislocation shearing in γ′ phases, facilitating the development of high-performance nickel-based superalloys.