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 slip was activated at the initial deformation stage, whereas basal slip and pyramidal 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.