Effect of ZrO₂ Nanoparticles on the Microstructure of Al-Si-Cu Filler for Low-Temperature Al Brazing Applications

In this study, the effect of ZrO₂ nanoparticles on Al-12Si-20Cu alloy has been studied as a filler metal for aluminum brazing. The microstructural and thermal characterizations are performed using X-ray diffraction (XRD), scanning electron microscope (SEM), and differential thermal analysis (DTA). The intermetallic compound (IMC) phases are identified by the energy-dispersive spectroscopy analysis coupled with the SEM. The filler spreading test is performed according to JIS-Z-3197 standard. XRD and SEM analyses confirm the presence of Si particles, the CuAl₂ (θ) intermetallic, and the eutectic structures of Al-Si, Al-Cu, and Al-Si-Cu in the Al matrix in the monolithic and composite samples. It is observed that when the ZrO₂ is added in the alloy, the CuAl₂ IMCs and Si particles are found to be dispersed uniformly in the Al matrix up to 0.05 wt pct ZrO₂. DTA results show that the liquidus temperature of Al-12Si-20Cu filler metal is dropped from ~806.78 K to 804.6 K (533.78 °C to 531.6 °C) with a lowering of 2 K (2 °C) in liquidus temperature, when the amount of ZrO₂ is increased up to 0.05 wt pct. It is also shown that the presence of ZrO₂ nanoparticles in the filler metal has no deleterious effect on wettability up to 0.05 wt pct of ZrO₂. The ultimate tensile strength and elongation percentage are also found to improve with the addition of ZrO₂ nanoparticles in the Al-12Si-20Cu alloy.