  Rapid solidification leads to unique microstructural features, where a less
studied topic is the formation of various crystalline defects, including high
dislocation densities, as well as gradients and splitting of the crystalline
orientation. As these defects critically affect the material's mechanical
properties and performance features, it is important to understand the defect
formation mechanisms, and how they depend on the solidification conditions and
alloying. To illuminate the formation mechanisms of the rapid solidification
induced crystalline defects, we conduct a multiscale modeling analysis
consisting of bond-order potential based molecular dynamics (MD), phase field
crystal based amplitude expansion (PFC-AE) simulations, and sequentially
coupled phase field -- crystal plasticity (PF--CP) simulations. The resulting
dislocation densities are quantified and compared to past experiments. The
atomistic approaches (MD, PFC) can be used to calibrate continuum level crystal
plasticity models, and the framework adds mechanistic insights arising from the
multiscale analysis.
