Abstract
The formation of cuboid fibers in Ni-Al-Mo and \([\alpha \beta ]_a[\alpha \delta ]_b\) superstructures in Bi-In-Sn ternary eutectics, driven by anisotropic interfacial energies, is investigated. To explain the formed superstructures ( \(\alpha\) , \(\beta\) and \(\delta\) solid phase arrangement mechanism), a morphology map is developed based on Directional Solidification (DS) simulation results. It is assumed that phase omission potentially occurs in locked grains, where interface anisotropy influences microstructure evolution in the following manner: Anisotropic \(\alpha \beta\) interfaces can drive the elimination of either the \(\alpha\) or \(\beta\) layers in \(\alpha \beta\) bilayers, while \(\alpha \delta\) interface anisotropy can lead to the removal of either the \(\alpha\) or \(\delta\) layers in \(\alpha \delta\) bilayers. This mechanism accounts for the formation of \(\alpha \beta \alpha \delta\) motifs in quasi-isotropic grains and the emergence of \(\alpha \beta \delta\) or \([\alpha \beta ]_a[\alpha \delta ]_b\) units in locked grains. It is additionally noted that \(\alpha \beta\) anisotropy in locked grains exerts a stronger influence on microstructural development than \(\alpha \delta\) anisotropy. Subsequent rotating DS (RDS) simulations provide additional supporting evidence for the assumed formation mechanisms. The radius profile of solidified floating grains exhibits a straight spiral pattern, whereas in locked grains, it follows a tilted spiral, with the tilt angle varying proportionally to anisotropy strength. Notably, the activation of anisotropy in any interface affects neighboring interfaces, even when they are modeled isotropically.
Graphical abstract