Interfacial reaction of intermetallic compounds of ultrasonic-assisted brazed joints between dissimilar alloys of Ti6Al4V and Al4Cu1Mg

Ultrasonic-assisted brazing of Al4Cu1Mg and Ti6Al4V using Zn-based filler metal (without and with Si) has been investigated. Before brazing, the Ti6Al4V samples were pre-treated by hot-dip aluminizing and ultrasonic dipping in a molten filler metal bath in order to control the formation of intermetallic compounds between the Ti6Al4V samples and the filler metal. The results show that the TiAl3 phase was formed in the interface between the Ti6Al4V substrate and the aluminized coating. For the Zn-based filler metal without Si, the Ti6Al4V interfacial area of the brazed joint did not change under the effect of the ultrasonic wave, and only consisted of the TiAl3 phase. For the Zn-based filler metal with Si, the TiAl3 phase disappeared and a Ti7Al5Si12 phase was formed at the interfacial area of the brazed joints under the effect of the ultrasonic wave. Due to the TiAl3 phase completely changing to a Ti7Al5Si12 phase, the morphology of the intermetallic compounds changed from a block-like shape into a lamellar-like structure. The highest shear strength of 138 MPa was obtained from the brazed joint free of the block-like TiAl3 phase.

► Ultrasonic wave accelerate diffusion rates of Si in molten filler metal at 420 °C.
► Si accumulate at Ti6Al4V/TiAl3 interface for less than 1 min.
► Ultrasonically treated Si react with TiAl3 phase to form Ti7Al5Si12 phase at 420 °C.