Laser-arc hybrid welding process and joint performances of 6106-T6 aluminum alloy profiles for high-speed trains
(2.Key Laboratory of Trans-Scale Laser Manufacturing Technology, Ministry of Education, Beijing, China 100124)
(3.Institute of Laser Engineering, Beijing University of Technology, Beijing, China 100124)
【Abstract】The hollow extrusion profiles of 6106-T6 aluminum alloy having a lock bottom structure were welded via fiber laser-cold metal transfer (CMT) arc hybrid welding, fiber laser-variable polarity tungsten inert gas (VPTIG) hybrid welding, and fiber laser-melt inert gas (MIG) hybrid welding. Subsequently, a hybrid welding joint with good forming properties and without clear defects was obtained by optimized welding parameters. Furthermore, the joint microstructure, tensile, and fatigue properties were studied, and the fatigue fracture mechanism and fracture morphology were analyzed. The results denote that the sizes of equiaxed grains at the center of the laser-CMT and laser-VPTIG hybrid welding joints gradually decrease from the upper part of the bead to the bottom. However, the sizes of the coarse equiaxed grains in the upper and lower parts do not change considerably, and the sizes of grains at the center of the laser-MIG hybrid welding joint are large. Furthermore, the tensile strength of the laser-CMT, laser-VPTIG, and laser-MIG hybrid welded joints are 213.0 MPa, 198.0 MPa, and 200.0 MPa, respectively. These values denote a certain degree of strength loss when compared with that of the base metal. The fatigue limits of the three hybrid welded joints are 105.00 MPa, 100.83 MPa, and 113.50 MPa, respectively. All the fatigue fracture positions are located in the columnar crystal zone at the fusion line of the welding joints. In addition, the fractures are dimpled, indicating a typical ductile fracture.
【Keywords】 laser technique; cold metal transfer welding; tungsten inert-gas welding of variable polarity ; melt inert-gas welding; 6106-T6 aluminum alloy; microstructures; joint performances ;
(Translated by ZHANG XY)
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