Heterogeneous deformation is particularly important in polycrystalline α-titanium, because the hexagonal crystal structure makes it more prone to polycrystalline compatibility issues. At the dislocation scale, this compatibility involves the process of how dislocations being initiated, propagating through grains, and the ability of grain boundaries accommodating dislocation shear in one grain with shear in its neighboring grain. To characterize the development of plasticity in a polycrystalline array due to dislocation nucleation, and slip across grains and grain boundaries, electron channeling contrast imaging (ECCI) based analysis is used, since this special scanning electron microscopy (SEM) technique possesses variety observation scopes, providing a linkage between the macro- and the micro- world. The first study presented a robust comparison between several techniques for the very first time: the digital image correlation (DIC), atomic force microscope (AFM), ECCI, and EBSD (cross-correlation). In this study, a Ti7Al alloy was deformed to 3% plastic tensile strain. The plasticity evolution of the sample was assessed through BESD-slip trace analysis, digital image correlation, and ECCI contrast analysis. The comparison between different methods revealed ECCI as a powerful technique in slip system identifications. The second project was more focused on the interactions between slip systems around the grain boundary area. The geometry of slip planes and grain boundaries was assessed as a function of depth, allowing the analysis of slip transfer parameters, including the geometric compatibility factor m’, the global Schmid factor of active slip systems, and the angles between slip planes. Locally accommodation behavior at the grain boundaries were revealed by ECCI.The third project was the identification of the propagation direction of a slip system across a polycrystalline grain patch by ECCI. Analysis indicated that slip bands would likely to become broader as they propagated further into the grain from the nucleation points, possibly due to cross-slipping. Together with the trace analysis, a better understanding of the development of plasticity within polycrystals during heterogeneous deformation was achieved.The highlight of this work not only focusing on the infinitesimal change in the local lattice structure in terms of dislocation nucleation and propagation in a grain, but also involves the plasticity development of deformation in a macroscopic view, such as the mechanism of dislocation across grain boundaries, and the estimation of overall deformation behavior within a region of grains. More importantly, together with other powerful characterization methods, ECCI in this study shows a strong potential that successfully links the macroscopic deformation with dislocation movement during the deformation.
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