Silver nanoparticle-assisted diffusion brazing of 3003 Al alloy for microchannel applications

In the current study, we investigated the effect of braze filler particle size and various processing parameters on vacuum diffusion brazing of thin foils of 3003 Al using a Ag nanoparticle (AgNPs) interlayer. All samples were brazed at 550 °C and 570 °C at heating rates of 5 °C/min and 25 °C/min under a pressure of 1 MPa. Differential scanning calorimetric results, involving 5 nm AgNPs, showed significant reduction in phase transformation temperature. Microstructures of brazed cross-sections revealed that nanoparticles aid formation of the joint at temperatures below the Al–Ag eutectic temperature of 567 °C. X-ray diffraction analysis of the interface showed the presence of δ-phase (Ag2Al) and μ-phase (Ag3Al). This was confirmed with energy dispersive spectroscopic analysis. A tensile strength of 69.7 MPa was achieved for a sample brazed at 570 °C with an interlayer of approximately 7 μm in thickness.

► 5 nm AgNPs showed size dependent melting behavior.
► 3003 Al alloy was brazed well below the Al–Ag eutectic (567 °C) temperature.
► Heating rate influenced the microstructural/phase changes at the bond interface.
► A 7 μm Ag interlayer resulted in shear stress of 69.7 MPa when brazed at 570 °C.
► Diffusion zone of ∼25 μm (one side) is a potential candidate for precision joining.