Formation of the Pattern of Al–Zn Dendrites Driven by Solid–Liquid Interfacial Energy

Solid-liquid interfacial energy critically governs microstructural evolution and the functional properties of materials during phase transition. Here, we quantitatively characterize the anisotropy of solid-liquid interfacial energy in an Al-30 wt % Zn hypoeutectic alloy using the improved equilibrium shape method, X-ray microcomputed tomography (CT), and digital image analysis. We obtained the two-dimensional (ε₄) and three-dimensional (ξ₁, ξ₂) anisotropy parameters by fitting droplet shapes with Fourier series and cubic harmonics. The interfacial energy is largest along the ⟨100⟩ and ⟨110⟩ directions, while the interfacial stiffness is smallest along the same directions. The near equivalence of stiffness between the ⟨100⟩ and ⟨110⟩ directions suppresses stable tip selection, destabilizes the growth front, and promotes hyperbranched, seaweed-like morphologies. This study provides quantitative evidence linking interfacial anisotropy to dendrite pattern formation and offers mechanistic insight into the morphological instability of Al-Zn alloys.