Crystal plasticity modeling of irradiation effects on flow stress in pure-iron and iron-copper alloys

• A dislocation-density based crystal plasticity model has been developed to quantify the variation of flow stress with irradiation in reactor pressure vessel steels.
• Isotropic interactions of dislocations with irradiation-damaged features such as precipitates and voids have been included in the model.
• Anisotropic interaction of dislocations with other dislocations and self-interstitial loops has been considered.
• Crystal plasticity simulations of polycrystalline aggregates with random orientations have been performed.
• Subsequently, the model has been validated with irradiated yield and flow stress data for pure-iron and iron-copper alloys.

The mechanistic modeling of irradiation induced embrittlement of reactor pressure vessel steels strongly depends on the precise evaluation of flow stress behavior. This requires accurate characterization of change in both the yield strength as well as the strain-hardening capacity. A dislocation-density based crystal plasticity model is thus developed in this work to quantify these variations with irradiation. The model considers the interaction between dislocations and irradiation induced defects such as self-interstitial atomic loops, vacancy clusters and precipitates to obtain flow stress variations in irradiated ferritic alloys. The model is calibrated and validated for polycrystalline pure-iron and iron-copper alloys, neutron-irradiated to different dose levels under typical pressure vessel operating conditions. A comparison with experimental results show that the model is able to quantify the changes in flow stress behavior accurately. At 0.2 dpa a loss of strain-hardening capacity beyond 2% strain is also obtained from the model. The yield strength increase with irradiation obtained from the model is also compared with analytical strengthening models based on Orowan’s equation.