Wetting and Spreading Of Liquid Metals Through Open Microgrooves and Surface Alterations

Abstract

Surface-tension-driven flows (isothermal or non-isothermal) of microlayers of complex liquids over substrates under reactive wetting conditions at elevated temperatures are greatly influenced by interface interactions and topography of surface alterations. For example, understanding of the spreading of molten metals over metal substrates with complex topography may be interpreted as spreading over multiple connected networks of open microchannels. Hence, understanding of the kinetics of wetting and spreading of such reactive systems through microchannels is of a key interest. This article provides an overview of wetting/spreading phenomena related to migration of molten metal microlayer over smooth, rough, and/or well-organized-topography surfaces, such as microchannels. Systems involving a liquid metal medium temperature range (at ∼850–873 K, Al-Si over Al), and a low temperature range (∼420–520 K, Pb-Sn and Ag-Sn over Cu and Cu-Sn) have been considered. Kinetics data involving triple-line movement and its modeling were supported by real-time in situ visualizations. Targeted applications of these fundamental studies involve the art of brazing of compact aluminum heat exchangers for HVAC&R (heating, ventilation, air conditioning, and refrigeration), thermal management for aerospace, and soldering processes (in particular lead-free) for electronics industries.