Revealing the deformation behavior among grains and phases of dual-phase Zr-2.5Nb alloy via quasi-in situ SEM-EBSD

This study systematically investigates the deformation and fracture damage mechanisms of a dual-phase Zr-2.5Nb alloy at room-temperature via quasi-in situ SEM-EBSD tensile testing. Slip trace analysis indicates that prismatic <a> slip was activated at the initial deformation stage, whereas basal <a> slip and pyramidal <a> slip were activated subsequently as the strain reached 6.3% and above. In-grain misorientation axis analysis not only further validated the accuracy of slip trace analysis, but provided a detailed insights into the intergranular deformation behavior among grains and phases. Local stress concentrating at the α-Zr/β-Zr phase boundary can promote the activation of slip in adjacent soft-oriented α-Zr grains. The results indicate that soft-oriented α-Zr grains effectively activate slip in surrounding grains. When the strain reaches 10.2% and above, the location of α-Zr/β-Zr phase boundary give priority for initiating microcrack due to the increased lattice distortion and the deformation incompatibility. Fracture morphology analysis reveals that the dual-phase Zr-2.5Nb alloy exhibits a mixed-mode fracture mechanism dominated by ductile fracture.