Use of Welding–Brazing Technology on Microstructural Development of Titanium/Aluminum Dissimilar Joints

A novel gas tungsten arc welding-brazing technology was utilized to butt weld titanium Ti-6Al-2Zr-Mo-1.5V to aluminum Al-5Mg-0.6Mn dissimilar alloys using AlSi5 filler metal. Microstructures of the weld zone were analyzed using optical microscopy and scanning electron microscopy. Phase constitution in the reaction zone was characterized by means of X-ray diffraction and energy-dispersive X-ray spectroscopy. The results showed that joint with good appearance can be obtained using the welding-brazing technology. A fusion zone with -Al and -Al+Mg2Si+silicon eutectic structure was formed at the aluminum side. Top surface of the titanium was partially melted and a thin titanium/aluminum fusion zone was formed between titanium and weld metal. In other regions, titanium and aluminum were brazed together by the formation of an unequal-thickness reaction layer. Five different intermetallic layers with Ti3.3Al, Ti3.3Al+Ti5Si3, TiAl+Ti5Si3, TiAl2+Ti5Al11+Ti9Al23+Ti5Si3, and TiAl3 are observed orderly from titanium to the weld metal in the titanium/aluminum fusion zone. Two intermetallic layers with Ti7Al5Si12 and TiAl3 are observed near the titanium/aluminum-brazed interface.