Influence of Nanosized AlN Powders on the Microstructure, Brazeability, and Tensile Properties of Al-based Filler for Low Temperature Al/Cu Dissimilar Brazing

This study examined the influence of nanosized aluminum nitride (AlN) powders (0, 0.01, 0.05, 0.10, 0.30, and 0.50 wt%), on an Al4047-based filler metal. Nanosized AlN powders were dispersed uniformly into the filler metal by a mechanical mixing and melting route using a stainless steel propeller. The influences of nanosized AlN powders on the melting behavior, microstructure, brazeability, and tensile properties were examined, and interfacial reactions between aluminum and copper were carried out. The experimental results showed that the thicknesses of Si and IMC keep decreasing with additions of nanosized AlN powders up to 0.10% in the brazing filler metal, which is attributed to the adsorption theory of nanosized AlN powders on the surface of Si and IMCs. In addition, the AlN-reinforced filler metal with 0.10 wt% samples showed a 2.61% enhancement in wettability due to the decreased surface tension in the filler metal matrix in the presence of nanosized AlN powders. Furthermore, aluminum to copper dissimilar brazing with 0.10 wt% AlN-reinforced filler metal showed a 16.07% improvement in the tensile strength compared to the 0% AlN filler due to the grain refinement of a filler metal matrix by the Orowan strengthening effect. Key words: brazing, AlN-reinforced filler, brazeability, tensile strength, grain refinement