The importance of the problem of hole-filling by a molten metal lies in the application of brazing for repairs in space, under microgravity conditions. The negligible effects of gravity and dominance of capillary forces can be approximated under terrestrial conditions, provided that the hole and the quantity of liquid are small, as quantified by the Bond number. In this paper, we report experimental results, modeling, and analysis of the hole-filling problem using the liquid aluminum brazing alloy on aluminum substrate. Depending on the hole size, the capillary driven flow may result in the hole being either filled or not filled. The equilibrium problem (energy minimization) has multiple solutions in some regions of the parameter space. Therefore, the experimental outcomes may depend on the availability of sufficiently strong perturbation, required to dislodge the system from a metastable equilibrium. We report good agreement between experimental results and theoretical/computational predictions. In general, a deeper and narrower hole favors the filled outcome.
This work offers an analysis of the wetting behaviour of the Zn-xAl filler metal spreading on the stainless steel. Effects of Al content on wetting kinetics and microstructures of the re-solidified filler metal were studied in this important system of dissimilar substrates. Experimental results have confirmed that the wetting of Zn-xAl filler metal on stainless steel features the trend of triple-line kinetics. In the main spreading phase, the spreading radius and time can be correlated with a power law of R n ∼ t, n = ∼ 0.4. The content of Al in the filler metal has a minimal effect on the value of n for the investigated range of Al concentrations. However, the spreading area of the filler metal after re-solidification decreases with an increase of the content of Al. Moreover, the thickness of the Fe-Al intermetallic layer at the cross-section increases with an increasing Al content.
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