Unique surface patterns emerging during solidification of liquid metal alloys

It is well-understood that during the liquid-to-solid phase transition of alloys, elements segregate in the bulk phase with the formation of microstructures. In contrast, we show here that in a Bi-Ga alloy system, highly ordered nanopatterns emerge preferentially at the alloy surfaces during solidification. We observed a variety of transition, hybrid and crystal-defect-like patterns, in addition to lamellar and rod-like structures. Combining experiments and molecular dynamics simulations, we investigated the influence of the superficial Bi and Ga2O3 layers during surface solidification and elucidated the pattern-formation mechanisms, which involve surface-catalysed heterogeneous nucleation. We further demonstrated the dynamic nature and robustness of the phenomenon under different solidification conditions and for various alloy systems. The surface patterns we observed enable high-spatial-resolution nanoscale-infrared and surface-enhanced Raman mapping, which reveal promising potential for surface- and nanoscale-based applications.

Automated summary

This study demonstrates the emergence of highly ordered nanopatterns on the alloy surfaces during solidification in the Bi-Ga alloy system. The pattern-formation mechanisms involving surface-catalyzed heterogeneous nucleation were elucidated through a combination of experiments and molecular dynamics simulations. The dynamic nature and robustness of the phenomenon under different solidification conditions and for various alloy systems were further demonstrated, showing promising potential for surface- and nanoscale-based applications.