Cleavage mechanism in vanadium alloys

The effect specimen geometry, loading rate and irradiation on the ductile-to-brittle transition in a V-4Ti-4Cr alloy were evaluated and modeled. Confocal microscopy-fracture reconstruction and SEM were used to characterize the sequence-of-events leading to cleavage, as well as the CTOD at fracture initiation. This alloy undergoes normal stress-controlled transgranular cleavage below a transition temperature that depends primarily on the tensile properties and constraint. Thus an equivalent yield stress model is in good agreement with observed effects of loading rate and irradiation hardening. Predicted effects of specimen geometry based on a critical stress-area criteria and FEM simulations of crack tip fields were also found to be in agreement with experiment. Some interesting characteristics of the fracture process are also described