Orientation determination and defect analysis in the near-cubic intermetallic γ-TiAl using SACP, ECCI, and EBSD

Crystal orientation and defect analysis for the commercially important γ-TiAl intermetallic compound is complicated by the near-cubic tetragonality of the L10 TiAl crystal structure. The selected area channeling pattern (SACP) method successfully reveals the γ-TiAl superlattice information, allowing accurate discrimination between the c and a directions that are commonly unattainable by the conventional electron backscattered diffraction (EBSD) method. Combination of this orientation information with crystal defect images obtained via the electron channeling contrast imaging (ECCI) method allows for rapid identification of active deformation systems in individual grains using a trace analysis scheme. Because SACP and ECCI are scanning electron microscopy (SEM) based techniques, analysis can be carried out on regularly shaped macroscopic samples, allowing association of the sample stress state and active defect systems. This has been shown in relation to defect analysis associated with strain transfer at grain boundaries. Additionally, the orientations determined via SACP have been used to correct EBSD data in order to reveal localized rotation due to retained strain within individual grains.