Observation and study of electrodeposition behavior of Sn–Ag eutectic alloys in DLM process

This study reveals a transient nucleation mechanism governing Sn–Ag eutectic formation, characterized by the dynamic evolution of pre-nucleation clusters (PNCs) through non-classical crystallization pathways in DLM process. Beyond macroscopic process optimization challenges, we systematically investigate nanoscale deposition mechanisms, proposing a multi-nucleation model under diffusion-limited growth constraints. Through in situ transmission electron microscopy (TEM), we experimentally validate the existence of “diffusion-controlled buffer zones” – transitional regions between nucleation-dominated and diffusion-limited regimes that exhibit hybrid kinetic-diffusive characteristics without forming distinct grain boundaries. The TEM observations demonstrate current density-dependent crystallization behavior: low-current conditions induce multi-site nucleation with edge amorphization-mediated crystal growth, while high-current regimes promote dendritic growth through diffusion-limited assembly. Intermediate current densities activate buffer zone dynamics, where concurrent kinetic-controlled nucleation and diffusion-driven growth coexist through structural fluctuation mechanisms. These findings establish a unified framework connecting interfacial thermodynamics, cluster dynamics, and macroscopic deposition morphology, providing critical insights for controlling eutectic microstructure in electrochemical manufacturing processes.