Irradiation in BCC materials: Defect-induced changes of the effective dislocation mobility and their relation with the dose-dependent fracture response

The mechanical response of nuclear structural materials and their lifetime are strongly affected by radiation effects. This influence is of concern, especially in body centered cubic materials, which exhibiting a well-defined ductile to brittle transition. The ductile to brittle transition temperature itself is dose-dependent and may rise to or above the room temperature. In the current work, irradiation effect is modeled to predict the dose-dependent changes of the effective dislocation mobility, represented by the Defect Induced Apparent Temperature shift (ΔDIAT). Mainly dislocation based crystal plasticity material model is used rather than a phenomenological approach. This material model accounts for both thermally activated dislocation mobility and dislocation mobility in an athermal regime of body centered cubic materials. The defect-induced evolution of ΔDIAT in turn analyzed and their relations with the fracture response are highlighted and discussed. •Temperature-dependent dislocation mobility in BCC materials.•Length dependent screw dislocation velocity and obstacle strengthening.•Dislocation-irradiation defect interaction to estimate irradiation hardening.•Suppression of secondary slip system participation due to irradiation.•Defect induced apparent temperature shift estimation based on the dislocation velocity field.