Modeling cyclic deformation of inconel 718 superalloy by means of crystal plasticity and computational homogenization

A crystal plasticity computational homogenization framework is proposed to simulate the cyclic deformation of polycrystalline alloys that exhibit Bauschinger effect, mean stress relaxation, ratcheting and cyclic softening, as it happens in many Nickel based superalloys. The response of the crystals is taken into account by means of a phenomenological viscoplastic crystal plasticity model that includes the contributions of isotropic softening and kinematic hardening. The effective behavior of the polycrystal is computed through the numerical simulation of a representative volume element of the microstructure. A linear cyclic jump approach is developed in order to reduce the computational cost for simulating a large number of cycles. The model is validated for a wrought polycrystalline IN718 superalloy subjected to cyclic deformation under strain control at different cyclic strain amplitudes with Rϵ 0 and −1. The actual microstructural features (grain size and orientation distribution) are included in the model through the representative volume element of the microstructure, while the parameters of the crystal plasticity model are determined using an inverse optimization strategy based on the Levenberg-Marquardt algorithm. The model is shown to predict accurately the evolution of the stress-strain hysteresis loops with the number of cycles, as well as the mean stress relaxation and the cyclic softening observed in the experiments.