Mechanical property degradation in irradiated materials: A multiscale modeling approach

High-energy particle irradiation of low stacking fault energy, face centered cubic (fcc) metals produces significant degradation of mechanical properties, as evidenced in tensile tests performed at or near room temperature. Post-irradiation microstructural examination reveals that approximately 90% of the radiation-induced defects in copper are stacking fault tetrahedra (SFT). Radiation damage is an inherently multiscale phenomenon involving processes spanning a wide range of length and time scales. Here we present a multiscale modeling methodology to study the formation and evolution of defect microstructure and the corresponding mechanical property changes under irradiation. At the atomic scale, molecular dynamics (MD) simulations have been used to study the evolution of high energy displacement cascades, SFT formation from vacancy rich regions of displacement cascades, and the interaction of SFTs with moving dislocations. Defect accumulation under irradiation is modeled over diffusional length and time scales by kinetic Monte Carlo (KMC), utilizing a database of displacement cascades generated by MD. The mechanical property changes of the irradiated material are modeled using three-dimensional dislocation dynamics (DD). Key input into the DD includes the spatial distribution of defects produced under irradiation, obtained from KMC, and the fate of dislocation interactions with SFTs, obtained from MD