Modeling Tensile, Compressive, and Cyclic Response of Inconel 718 Using a Crystal Plasticity Model Incorporating the Effects of Precipitates

Abstract

A comprehensive elasto-plastic polycrystal plasticity model is developed for Ni-based superalloys. To demonstrate the microstructure sensitive predictive characteristics, the model is applied to an Inconel 718 (IN718) superalloy that was produced by additive manufacturing (AM). The model with the same set of material and physical parameters is compared against a suite of compression, tension, and large strain cyclic mechanical test data applied in different AM build directions. The model embeds the contributions of solid solution, precipitates shearing, and grain size and shape effects into the initial slip resistance. The hardening law is based on the evolution of dislocation density. It is demonstrated that the model is capable of predicting the particularities of both monotonic and cyclic deformation to large strains of the alloy including decreasing hardening rate during monotonic loading, the non-linear unloading upon the load reversal, the Bauschinger effect, the hardening rate change during loading in the reverse direction as well as anisotropy and concomitant microstructure evolution. The microstructure constituents and behavior of IN718 under these conditions is similar to other Ni-based superalloys, and therefore, it is anticipated that the general model developed here can be applied to other superalloys fabricated using AM and other approaches. Additionally, the material is tested in fatigue and results are presented and discussed.