In-situ diffraction based observations of slip near phase boundaries in titanium through micropillar compression

We investigate local deformation within a dual-phase Ti6242 alloy by considering the interaction between α orientation (i.e., slip system) and the presence of β phase (i.e., fraction and morphology), and the corresponding evolution of stored dislocations. In-situ micropillar compression combined with micro-Laue diffraction and high angular resolution electron backscatter diffraction (HR-EBSD) shows that the high rate of geometrically necessary dislocation (GND) accumulation was observed in basal-slip oriented pillar, while easy formation of glide step with minimal GND accumulation was found in prism-slip oriented pillar. The difference is explained due to the role of the phase boundary for these slip configurations, where local stress concentrations can arise even in pillar with easy slip orientation (i.e., prism slip) if the phase boundary acts as a barrier to slip and results in inhomogeneity of local deformation. This study reveals significance of β phase in potentially modulating the local dislocation based hardening and hence local stress states within Ti polycrystalline aggregate.