Application of Precession Electron Diffraction in Deformation Studies of Advanced Non-Ferrous Structural Alloys

It is well known that the mechanical properties of structural metallic materials are influenced considerably by the attending microstructural features.  However, it is often difficult to quantitatively interpret the deformation accumulation with respect to microstructural features while determining mechanisms that are dominant during deformation. While some modern techniques, including in-situ tensile testing in a scanning electron microscope equipped with orientation microscopy capabilities, can be used interpret the earliest stages of deformation studies, such techniques are limited to “hot spots” with minimal strain, and are limited in their spatial resolution. A recently developed TEM-based orientation microscopy technique called precession electron diffraction (PED) enjoys high spatial resolution (2 nm), high angular resolution (~0.8°) and can be used to characterize materials and microstructures whose deformation ranges from very low levels to a very high degrees of deformation. While these capabilities have been developed for materials produced via severe plastic deformation, they also provide the opportunity to explore materials that have been historically difficult to study in a quantitative manner, yet are important to aerospace applications including metastable beta titanium alloys with refined alpha precipitates and gamma+gamma’ Ni-based superalloys. Spatially varying dislocation densities will be extracted from various aerospace materials, and the results coupled with strengthening mechanisms to demonstrate the versatility of this novel approach.