(651f) Emergence of Faceted Spiral Patterns during Eutectic Crystallization
AIChE Annual Meeting
2019 AIChE Annual Meeting
Particle Formation and Crystallization Processes from Liquids, Slurries, and Emulsions
Thursday, November 14, 2019 - 9:48am to 10:09am
Herein, we demonstrate the twoâstep formation pathway of faceted spiral eutectics upon directional solidification in the ZnâMg alloy system. These twoâphase ZnâMgZn2 microstructures are periodic, metastable, and intrinsically chiral. We trace the emergence of such structures from the parent liquid through a correlative and multiscale investigation encompassing 3D measurements â namely Xâray nanoâtomography aided by machine learning and electron backscatter diffraction â along with in situ synchrotron Xâray diffraction and atomicâresolution electron microscopy. Altogether, the results reveal the morphological and heteroepitaxial relationships between the eutectic phases and the origin of spiral growth. The results also identify a thusâfar neglected nucleation mechanism involving crystallographic defects within 'hidden' polytetrahedral phases, which provide a template for spiral eutectic crystallization. Our findings provide the necessary benchmark data for simulations of complex crystallization patterns, thus expanding the horizon for the bottomâup design of nextâgeneration alloys.