Effects of Alloyed Fluxes on Spreading Behavior and Microstructures of Aluminum–Titanium TIG Brazing Interface

Alloyed fluxes consisting of the non-corrosive aluminum brazing potassium fluoroaluminate flux and alloyed elements Cu, Zr and Ni were firstly developed and studied for aluminum–titanium TIG arc brazing. Not only the alloyed fluxes can promote wetting of molten aluminum filler on the titanium, but suppress the formation of the intermetallic compound (IMC) layer as well. Results indicated that the alloyed fluxes exerted different influences on spreading areas. Comparing with the unalloyed flux, the spreading area of aluminum on titanium with Cu alloyed flux increased significantly, from 116 to 143 mm². Moreover, evident differences in IMC thickness were observed corresponding to various fluxes. The IMC thickness rose dramatically at first and then declined with the increasing concentration of alloying element. The IMC can be reduced effectively by employing the fluxes with 50% Cu or Ni. The root cause is attributed to the Cu and Ni distribution in the aluminum brazing joint.