Dislocation density based crystal plasticity model incorporating the effect of precipitates in IN718 under monotonic and cyclic deformation

A dislocation density based crystal plasticity model is developed to account for the precipitate induced cyclic softening in IN718. The new model treats the interaction between the precipitates and the dislocations using a probabilistic approach. It is also capable of capturing the reduction in the effective size of the precipitates due to reversible dislocations shearing through them. Further, the phenomenological model accounts for the heterogeneous accumulation of dislocations in the microstructure (i) as a function of distance to the nearest grain boundary and (ii) the interparticle spacing within a grain. The developed model is used to simulate the macroscopic mechanical response of IN718 under a series of monotonic and cyclic loads at different strain rates and alternating strain levels, respectively. Model predictions of macroscopic behavior are shown to be in good agreement with experimental data. They can capture the initial hardening and subsequent softening during cyclic loading for several strain amplitudes. Sensitivity analyses have been performed to understand the influence of grain size, reversible dislocations, and the size of the precipitates.