On the mechanisms and mechanics of fracture toughness of a V–4Cr–4Ti alloy

Effects of irradiation and crossrolling on fracture toughness–temperature curves of the program heat of the V–4Cr–4Ti were evaluated. The alloy undergoes normal stress controlled cleavage fracture at low temperatures and ductile tearing fracture at higher temperature. It appears that crossrolling lowers the cleavage transition temperature. A critical stress–critical-stressed area cleavage criterion is used to model toughness–temperature curves in the cleavage transition, including the effect of specimen size. Irradiation induced increases in the transition temperature are accurately predicted by an equivalent yield stress model. Ductile tearing toughness is also degraded by irradiation, correlating with reduced uniform strains measured in tensile tests. Large cleavage transition temperature shifts and ductile toughness decreases may limit the application of V–4Cr–4Ti alloys for service in low-to-intermediate temperature irradiation environments.