MECHANICAL CONSTITUTIVE MODELING OF SELF-IRRADIATED PLUTONIUM ALLOYS

A dislocation-based crystal plasticity constitutive model is developed to predict the microstructural evolution and macroscopic mechanical behavior of self-irradiated, aged plutonium alloys. The model incorporates fundamental microscopic mechanisms, including slip system activation, dislocation multiplication and annihilation, and irradiation-induced defect evolution. Furthermore, it accounts for the interaction between dislocations and radiation defects through a proposed hardening and evolution rate theory. Implemented within a finite element method (FEM) framework, the model parameters are calibrated against experimental tensile data for unaged plutonium alloys. The model is subsequently applied to predict the stress-strain response of single-crystal plutonium alloys across various aging times, temperatures, and strain rates. Results indicate that aged plutonium alloys exhibit a distinct softening-then-hardening post-yielding behavior due to dislocation-defect interactions, which is accompanied by plastic deformation localization. For cases of accelerated irradiation conditions, the alloys present a smooth elastic-plastic transition, revealing the concurrent effects of defect generation and dislocation-defect interaction. This work provides a theoretical foundation and computational tools for the long-term service safety assessment of plutonium alloy components.