[SY-B4] Physically based prediction of radiation hardening: application to steels and model alloys
Based on a multiscale modeling framework, it is shown that radiation hardening can be rationalized in several industrial materials and model alloys. Microstructure features of the as-received materials are first considered for the assessment of the yield stress prior to irradiation. The later can be decomposed into two contributions: short-range stresses induced by local obstacles (such as forest dislocations, precipitates, etc.) and long-range stresses resulting from sub-grain dislocation walls and grain boundaries. Introducing radiation defects as local obstacles, the same methodology can be employed to predict the yield stress of the irradiated materials. The considered radiation defects are solute clusters (SCs) and Dislocations Loops (DLs). SCs are assumed to be spherical coherent precipitates that can be sheared by dislocations with a given shear resistance, computed from atomistic simulations. This resistance is used in Dislocations Dynamics (DD) simulations to compute hardening induced by SCs. The sizes and densities implemented in DD simulations are those given by experiment (TEM, APT, SANS etc.). The contribution of DLs is computed from DD simulations. Upon interaction with mobile dislocations, small DLs are absorbed leading to strong pinning and high hardening level, while large DLs experience classical dislocation-dislocation interactions (junction, annihilation, etc.). The yield stress of the irradiated materials is predicted using the constitutive equations of radiation hardening induced by SCs and DLs.
Several FeCr, FeMnNi model alloys and some RPV steels are considered for the validation of the model. It is shown that local obstacles (present before irradiation) may have a significant effect on radiation effects on the mechanical properties: radiation hardening is not independent of the initial yield stress. With almost no adjustable parameters, the predicted increase in the yield stress is found in close agreement with experiment.
Several FeCr, FeMnNi model alloys and some RPV steels are considered for the validation of the model. It is shown that local obstacles (present before irradiation) may have a significant effect on radiation effects on the mechanical properties: radiation hardening is not independent of the initial yield stress. With almost no adjustable parameters, the predicted increase in the yield stress is found in close agreement with experiment.