Process, microstructures and mechanical properties of Al/Ti dissimilar metals with laser/laser-CMT hybrid welding-brazing

ER4047 wire and powdered Nocolok brazing flux were selected as filler materials, and two welding methods, laser fusion brazing and laser-CMT hybrid welding-brazing, were used to join 5A06 aluminum alloy and Ti6Al4V alloy. The microstructure and mechanical properties of the two welded joints were compared and analyzed. The results show that continuous and stable welded joints can be easily obtained by laser welding-brazing and laser-CMT hybrid welding-brazing under appropriate welding process. The microstructure of the middle part of the weld of aluminum/titanium laser welding-brazing and laser-CMT hybrid welding-brazing is α-Al solid solution and Al-Si eutectic structure. Both laser welding-brazing and laser-CMT hybrid welding-brazing have the thickest interface reaction layer on the upper surface of titanium alloy, with the thickness of less than 10 and 6 μm respectively. The interface on the titanium side of the laser brazed weld is mainly serrated, and the interface on the titanium side of the laser-CMT composite brazed weld is mainly lamellar. The joints of laser welding-brazing and laser-CMT hybrid welding-brazing welding are fractured in the weld zone, and the average tensile strength of the joints are 252 and 209 MPa respectively. The tensile strength of laser welding-brazing is 20% higher than that of laser-CMT hybrid welding-brazing. The efficiency of laser-CMT hybrid welding-brazing is about 1.5 times higher than that of laser welding-brazing.