This report offers an insight into the study of a molten Al-Si-K_xAl_yF_z braze behavior under terrestrial, and microgravity conditions on the International Space Station (ISS). The BRazing of Aluminum alloys IN Space (SUBSABRAINS) project seeks to provide insight into the surface tension driven capillary flow of a braze alternately exposed to terrestrial and ISS conditions. This work is funded by NASA's Physical Sciences Research Program (NASA Grant# NNX17AB52G) and Roscosmos Research ISS Program (space experiment REAL). In this paper, a brief summary of only one aspect of the studied phenomena is discussed. The SUBSA multiple sealed ampoules, tested in a sequence, carry the aluminum/alumina substrates and Al-Si-K_xAl_yF_z braze exposed to a heating/cooling cycle between 70 and ～1100 deg F (21 to ～600 degrees Celsius) in ultra-high purity Nitrogen or a high vacuum. The experiments have been executed at the ISS and returned to Earth for detailed study, including the surfaces topography, microstructure, electron microscopy studies, numerical simulation based on a developed phase-field modeling theory and Surface Evolver. The study indicates that a combined surface tension and flow conditions may lead to different patterns of phase segregation, various levels of interface dissolution, variable advancing vs. receding contact angles and the triple line locations.
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