Study on laser welding-brazing of zinc coated steel to aluminum alloy with a zinc based filler

Laser welding-brazing (LWB) technique with CW Nd:YAG laser was used for lap joining of zinc coated steel (DP600) with aluminum alloy (AA6016) using a filler wire composed of 85% Zn and 15% Al. LWB was performed with varying laser power, brazing speed, and wire feed speed. The microstructure and composition analyses of the brazed joints were examined using SEM and EDS while the mechanical properties were measured in the form of micro-hardness and tensile strength. The thickness of reaction layers formed along the steel-seam interface was in the range of 3-23 mu m, and it varied with the brazing speed. The average micro-hardness value of this layer was 348 HV, compared to 150 HV in brazed seam and 230 HV in steel matrix. It has been found that joints produced with heat inputs between 60 and 110 J/mm exhibited higher mechanical resistance of about 220 MPa and the failures occurred away from the joints on aluminum side. The corresponding brazing speeds are between 0.5 and 0.8 m/min and the thickness of the layer produced ranged between 8 and 12 mu m. (C) 2010 Elsevier B.V. All rights reserved.