Effect of Ni–Al 2 O 3 nanocomposite coating thickness on transient liquid phase bonding of Al 6061 MMC

Transient liquid phase diffusion bonding of Al 6061 containing 15 vol.-% alumina particles was carried out as a function of interlayer thickness. Electrodeposited Ni coatings containing 18 vol.-% nanosized alumina particles with thickness ranging from 1 to 13 μm was used as the interlayer. Joint formation was attributed to the solid state diffusion of Ni into the Al 6061 metal matrix base metal followed by eutectic formation, base metal dissolution and isothermal solidification at the joint interface. Examination of the joint region using scanning electron microscopy, wavelength dispersive spectroscopy and X-ray diffraction showed the formation of intermetallic phases such as AlFe₃Si, Ni₁₇Al_3·9Si_5·1O₄₈ and Ni₃Si within the joint zone. The results indicated that a maximum joint strength of 92% of the base metal shear strength can be obtained if an 11 μm thick Ni–Al₂O₃ nanocomposite coating is used as the interlayer.