The structural design of dual-phase or multiphase advanced alloys depends on understanding the coordinate deformation of various phases under applied stress, in which experimentally disclosing the microscopic picture of dislocation plasticity transportation is critical. In this study, in situ transmission electron microscope tensile tests were used to examine the dislocation behaviors occurring during the deformation of a dual-phase Ti-10(wt.%) Mo alloy having hexagonal close-packed α phase and body-centered cubic β phase. The findings demonstrated that the dislocation plasticity preferred to transmit from alpha to alpha in the longitudinal axes of each plate, regardless of where dislocations were formed. Dislocations for the α phase were initially activated in the α phase and migrated along the plate’s longitudinal axis. Specific sites with local stress concentration were created at the intersection of various alpha plates, which made it easier to transfer dislocation plasticity from one plate to another. Nearby α plates’ majority of newly excited dislocations kept moving in a longitudinal direction. Dislocations pinned on the α-β phase boundary of the β phase would decrease resistance as the stress grew and migrate along the longitudinal direction in the α phase. Dislocation slips occurred in multiple directions as a result of α plates’ variable orientation, which might be advantageous for uniform plastic deformation. The findings provide insight into the use of microstructure engineering to enhance the mechanical properties of materials.

Understanding the coordinated deformation of multiple phases under applied stress is crucial for the structural design of dual-phase or multiphase advanced alloys. In this study, in-situ transmission electron microscope tensile tests were performed to investigate the dislocation behaviors and the transportation of dislocation plasticity during the deformation of a dual-phase Ti-10(wt.%) Mo alloy having hexagonal close-packed α phase and body-centered cubic β phase. We demonstrated that the dislocation plasticity preferred to transmit from alpha to alpha phase along the longitudinal axis of each plate, regardless of where dislocations were formed. The intersections of different α plates provided local stress concentration that facilitated the initiation of dislocation activities from there. Dislocations then migrated along the longitudinal axis of α plates and carried dislocation plasticity from one plate to another through these intersections as well. Since the α plates distributed in various orientations, dislocation slips occurred in multiple directions, which is beneficial for uniform plastic deformation of the material. Our micropillar mechanical testing further quantitatively demonstrated that the distribution of α plates and the α–α plates’ intersections plays important role in tuning the mechanical properties of the material.