Abstract Microscopy and materials characterization can be optimized through the application of techniques that enable nanoscale observations within large areas, to help understand the contextual relationship between the local nanostructure and global microstructure. In this work, we demonstrate that electron channeling contrast imaging (ECCI) can now be deployed in a controlled manner, exploiting advances in electron channeling pattern (ECP) formation and rapid interpretation using new software tools. We demonstrate this capability via four case studies: single-crystal silicon, dislocations in GaAs, a deformed nickel polycrystal, and deformed olivine.
Abstract Grain rotation under concurrent grain boundary (GB) migration can be observed in experiments, but poses a challenge in simulations. The need to resolve atom-scale structures while tracing GB migration over extended time scales defy most modeling approaches, including molecular dynamics (MD). In this work, phase field crystal (PFC) modeling is adopted as it permits the required combination of high spatial resolution and extended time spans, orders of magnitude longer than what is feasible in MD. The possibility to trace grain rotation by PFC is demonstrated and it is shown that grain rotation is increasingly pronounced as the grain size is reduced and while misorientation is small. In contrast, grains demarcated by high-angle GBs exhibit negligible rotation during migration. The ability of small grains to rotate is shown to depend on the extent of GB dislocation reactions. The results also highlight that classical grain growth kinetics fail to apply under rotation of small grains with low-angle GBs.
Abstract We use Dark‑Field X‑ray Microscopy to image dislocation ensembles in bulk Al1050 during the first 2 % of tensile deformation. A beam‑stop in the back focal plane suppresses bulk‑lattice diffraction, enhancing contrast from the strained regions surrounding dislocation cores. Layered rocking scans provide 3D point‑cloud representations of the dislocation configurations in two neighbouring grains. The measurements reveal directional dislocation arrangements, partial alignment with crystallographic slip‑plane traces, and the early formation of low‑angle boundaries.
Abstract The review presents how contact of solid interfaces to liquid recycled Al alloys contribute to purification but also contamination of Al alloys and how interfaces can affect the microstructure evolution during solidification. Interaction at interfaces as wetting, reactive layer formation and dissolution are especially considered. Benefits of targeted utilization of interfaces for dealing with impurity elements and inclusions in recycled Al alloys are discussed.
Abstract The evolution of microstructure and mechanical properties during annealing has been studied in a 90% rolled CoFeMnNi-5Cr-5Al-1C multi-principal element alloy. The rolled microstructure is observed to be strongly heterogeneous, comprising twinned regions and shear bands, layers of mixed orientations with high frequencies of high-angle boundaries, and extended regions dominated by low-angle boundaries. During annealing at 800 °C, shear bands and layers of mixed orientations act as preferential sites both for nucleation of recrystallized grains and for precipitation of B2 and carbide particles. Tensile tests conducted at room temperature reveal high yield strength (∼800 MPa) and good uniform elongation (14% and 17%) in partially recrystallized samples obtained by annealing for 30 min and 1 h.
