Visco-plasticity phase-field simulation of the mechanical property and rafting behavior in nickel-based superalloys

Formation of raft structure and widening of γ matrix width are usually observed in the nickel-based single crystal superalloys at high temperature loading conditions. But the effect of this rafting behavior on the mechanical property is still ambiguous until now. In the present study, a visco-plasticity phase-field model that based on the classical flow theory and the creep theory is developed to investigate the mechanical property and rafting behavior of nickel-based superalloys. The relationship between the yield stress and γ matrix width is firstly paid attention through a series of tensile tests. Simulations that have considered the effect of Orowan stress indicate that the yield stress of γ′/γ microstructures decreases with the increase of γ matrix width. When the matrix width exceeds to a critical value, the yield stress of the microstructure becomes constant. The presence of the yield stage during the tensile process is related to the active slip systems shearing into γ′ precipitates. Then a damage law is introduced to assess the creep resistance of the material. Our simulations precisely predict the creep life and present the shape of strain curves. The evolution rule of strain curves is revealed by analyzing the distribution of plastic strain field and equivalent stress field. Furthermore, simulations that consider four γ′ variants and only one γ′ variant are compared. Results indicate that a stable raft structure can enhance the creep resistance of the superalloys.