Precipitation of γ″ in Inconel 718 alloy from microstructure to mechanical properties.

Abstract This paper presents a coupled approach able to describe γ ″ precipitation evolution and associated yield strength after various heat treatments in Inconel 718 alloy. The precipitation state is modeled via the implementation of classical nucleation and growth theories for plate-shaped particles. The precipitation model is validated through small-angle neutron scattering and transmission electron microscopy experiments. The precipitation size distribution serves as an input parameter to model the yield strength using a micromechanical model based on shear and bypass mechanisms accounting for the particular shapes of the precipitates. Results are in good agreement with measured yield stresses for various precipitation states. A complete simulated TTT diagram of the γ ″ phase with the associated yield strength is proposed. The coupled model is finally applied to a series of non-isothermal treatments representative of welding (or additive manufacturing) from the peak aged state.