Effect of copper alloyed flux on aluminum/titanium welded-brazed joint

One of the non-corrosive Nocolok flux for brazing of aluminum was developed by alloying with Cu and applied to TIG welding-brazing of aluminum-titanium butt joint. Compared with the Nocolok flux,the alloyed flux can promote wetting of molten aluminum filler on the titanium,suppress the formation of the intermetallic compounds（ IMCs） layer,improve joint strength and influence the joint fracture mode. The positive effect of element Cu on wettability is related to the decrease in the solidus or liquid temperature and the metallic oxides existed in the alloyed element. The changes in IMC thickness and joint strength are attributed to the combination effect of the chemical barrier and interface alloying of element Cu.