In-situ investigation of coordinated deformation behavior of Ti-6242S alloy with duplex microstructure

In this work, the coordinated deformation behavior related to slip activation, slip transfer and microcrack growth of Ti-6242S alloy with duplex microstructure was investigated through the in-situ tensile testing. It was found that the deformation process of duplex microstructure can be divided into three stages: slip deformation, the formation of slip band and microcrack nucleation, crack propagation and fracture. And single slip was the dominant slip mode, and multiple slip was the auxiliary slip mode. During the initial tensile stage, the slip lines appearing within colony alpha were shallower than those within primary alpha owing to the hindering of alpha/beta interface. The slips penetrated across the entire colony region by straight line. This was because there existed a Burgers orientation relationship between lamellar alpha and beta layer, and the orientation of lamellar alpha was similar. Meanwhile, the common crystal plane between adjacent grains can still provide good condition for slip transfer when the grain boundary was greater than 15 degrees . Moreover, the slip transfer between adjacent slip systems was more prone to occur when there existed good geometric compatibility and high Schmid factor of exit slip system, which provided coordinated deformation between adjacent grains and avoided stress concentration. However, due to the existence of incompatible deformation, the cracks were generated at the stress concentration areas and then grew along the grain boundary or localized slip band.