Thermal Conductivity Assessment and Mechanical Strength of Braze-Welded AA1050 Aluminum in Cooling Duct Applications

Abstract

This study evaluates the mechanical integrity and heat-transfer performance of braze-welded AA1050 lap joints for cooling-duct applications using Al–Si 4047 filler and NOCOLOK® potassium-fluor aluminate flux. A two-factor, three-level Taguchi L9 design varied wire diameter (1.6, 2.4, 3.2 mm) and hole diameter (5, 7, 9 mm) in a plug-brazing configuration. This research is focused on the mechanical and thermal evaluation of the joint. Therefore, it gives a clear indication of the characteristic behavior of the welded joints.  Mechanical testing showed a clear optimum at 2.4 mm wire with a 7 mm hole, achieving the highest shear load (≈3150 N) and the most stable response to noise factors. Thermal-conductivity measurements indicated that well-filled, low-porosity joints at the same condition retained conductivity near the upper end observed for brazed joints (≈200 W·m⁻¹·K⁻¹) compared with the base AA1050 (≈222 W·m⁻¹·K⁻¹), confirming that interfacial porosity and Si-rich eutectic phases are the primary causes of the modest reduction. ANOVA from the Taguchi analysis identified wire diameter as the dominant factor, followed by hole diameter, highlighting the importance of balancing filler volume with joint geometry to suppress shrinkage porosity and ensure complete wetting. Overall, the optimized condition simultaneously maximizes shear strength and thermal conductance, meeting the dual requirements of structural robustness and efficient heat dissipation in aluminum cooling-duct assemblies.