Estimation of Dislocation Densities With Nondestructive Scanning Electron Microscope Techniques: Application to Gallium Nitride.

Characterizing threading dislocations (TDs) in gallium nitride (GaN) semiconductors is crucial for ensuring the reliability of semiconductor devices. The current research addresses this issue by combining two techniques using a scanning electron microscope, namely electron channeling contrast imaging (ECCI) and high-resolution electron backscattered diffraction (HR-EBSD). It is a comparative study of these techniques to underscore how they perform in the evaluation of TD densities in GaN epitaxial layers.

Secondary Hardening of a High-N Ni-Free Stainless Steel.

High-N Ni-free stainless steels are used for their excellent mechanical properties combined with their high corrosion resistance, especially for biomedical applications. Even though it is well-known that secondary hardening during annealing after cold working has been observed in many materials, this phenomenon was not reported for these materials, one of the best known being Biodur108©, although numerous efforts have been made to increase its hardness. In this work, thermomechanical treatments at low temperature of cold-deformed Biodur108© were conducted to increase the hardness.

In Situ Macroscopic Tensile Testing in SEM and Electron Channeling Contrast Imaging: Pencil Glide Evidenced in a Bulk β-Ti21S Polycrystal.

In this paper, we report the successful combination of macroscopic uniaxial tensile testing of bulk specimen combined with In situ dislocation-scale observations of the evolution of deformation microstructures during loading at several stress states. The dislocation-scale observations were performed by Accurate Electron Channeling Contrast Imaging in order to follow the defects evolution and their interactions with grain boundaries for several regions of interest during macroscopic loading. With this novel in situ procedure, the slip systems governing the deformation in polycrystalline bulk β-Ti21S are tracked during the macroscopic uniaxial tensile test.

A Dislocation-Scale Characterization of the Evolution of Deformation Microstructures around Nanoindentation Imprints in a TiAl Alloy.

In this work, plastic deformation was locally introduced at room temperature by nanoindentation on a γ-TiAl-based alloy. Comprehensive analyses of microstructures were performed before and after deformation. In particular, the Burgers vectors, the line directions, and the mechanical twinning systems were studied via accurate electron channeling contrast imaging.

Advancing FIB assisted 3D EBSD using a static sample setup.

A new setup for automatic 3D EBSD data collection in static mode has been developed using a conventional FIB-SEM system. This setup requires no stage or sample movements between the FIB milling and EBSD mapping. Its capabilities were tested experimentally on a coherent twin boundary of an INCONEL sample.