Effect of dislocation slip on in-situ tensile fracture of vanadium alloys after helium/self-ion irradiation

Research on tensile fracture of vanadium alloys after irradiation would help evaluate their mechanical properties and service life in extreme environments of fusion reactors, thereby ensuring the safety and reliability of the materials. This study investigated the effect of dislocation slip on the fracture of irradiated V-4Cr-4Ti through in-situ tensile testing under transmission electron microscopy (TEM). The results showed that He⁺ and V⁺ ions irradiation of V-4Cr-4Ti generated dislocations loops and helium bubbles. During subsequent in-situ tensile deformation, dislocation slip was the primary deformation mode under tensile load, while helium bubbles, due to size constraints, exhibited no significant deformation. During the loading process, multiple slip systems were activated. Based on the Critical resolved shear stress (CRSS) analysis, the slip primarily occurred along the (1 −1 0) plane, while fracture mainly occurred along the (−1 −1 2) plane. The necking phenomenon after fracture was not apparent, indicating that the irradiated sample had a very high yield stress. Additionally, when the sample was close to fracture, dislocations in regions with fewer defects experienced less resistance and thus slid over greater distances. This study utilizes in-situ tensile testing under TEM to observe dislocation slip interacts with defects during deformation of irradiated V-4Cr-4Ti, revealing its influence mechanisms on fracture behavior of material.