Microstructure and mechanical properties of Ti–6Al–4V/Al1060 joints by ultrasonic-assisted brazing in air

Ultrasonic-assisted brazing of Ti–6Al–4V alloy and Al1060 alloy was carried out in air and by filling with Al–12Si wt% alloy at 620 °C. The ultrasonic introduced into brazing could break the oxide films of base materials and change the microstructure of the joint alloy. The surface oxide film of Ti–6Al–4V side showed a great effect on joint strength. The removal of this oxide film was determined by the formation of abnormal pits on the Ti–6Al–4V surface by means of ultrasonic effects of cavitation, which could act as the initial source of substrate oxide undermining to make the oxide film floating in liquid joint alloy, and the oxide film was broken completely by subsequent second ultrasonic vibration. Intermetallic compounds Ti7Al5Si12 were the primary reaction phases and the steady interfacial microstructure was Al–12Si/Ti9Al23/Ti7Al5Si12/Ti–6Al–4V between liquid Al–12Si and solid Ti–6Al–4V. The formation and growth of the intermetallic compounds were mainly Si-diffusion-controlled processes. The shear strength of the joints obtained from a wide range of technological parameters could reach to ∼68±2.3 MPa.

► Ultrasonic effects in the liquid alloys could break the oxide film of base materials.
► Oxide film of Ti–6Al–4V showed a great effect on joint strength.
► Abnormal pits formed on the Ti–6Al–4V surface by cavitation erosion.
► Pits acted as the initial source of substrate oxide undermining.
► Formation and growth of interfacial IMC were Si-diffusion-controlled processes.