Abstract
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 modelling analysis consisting of bond-order potential-based molecular dynamics (MD), phase field crystal-based amplitude expansion simulations, and sequentially coupled phase field–crystal plasticity 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.This article is part of the theme issue ‘Transport phenomena in complex systems (part 2)’.
Highlights
Several industrial processes, such as thermal spray coating deposition [1], certain welding techniques [2] and metal additive manufacturing [3], operate under rapid solidification conditions
In the molecular dynamics (MD) simulations, a simulation box with liquid in the middle, and the resulting rapid solidification at early time (0.1 ns) and fully solidified structures are shown in figure 3 for pure aluminium and Al–1at%Cu
We presented a multiscale analysis of crystalline defect formation in pure aluminium and dilute Al-Cu alloys using MD on smallest scales, PFC–AE simulations on intermediate scales, and a coupled phase field–crystal plasticity (PF–CP) simulation scheme on largest scales
Summary
Several industrial processes, such as thermal spray coating deposition [1], certain welding techniques [2] and metal additive manufacturing [3], operate under rapid solidification conditions. An overlooked, yet important, feature of these microstructures is the formation of various types of crystalline defects [8] These include trapping of excess point defects [9], formation of high dislocation densities [10,11,12], cavitation or microvoiding [10,13,14], high microstructural (type II-III) residual stresses [15,16] and so-called lattice orientation gradients [17]. These crystalline defects critically affect the material’s mechanical properties and performance. In metal additive manufacturing of aluminium alloys, one of the key issues is controlling rapid solidification induced shrinkage and the associated cracking [21,22]
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