The Research On Laser Welding Process Of 6061 Aluminum Alloy For High-Speed Trains

6061 aluminum alloy is a typical medium-strength aluminum alloy based on Al-Mg-Si. Because of its characteristics of good weld formability,excellent weldability and suitable price,6061 aluminum alloy has been applied to kinds of industries.Compared with traditional welding technology of aluminum alloy, laser welding has many advantages such as high energe density, high welding speed, small welding deformation, and small hear input.In this paper, based on the ANSYS software,in which numeral for welding calculation method is employed,Gauss heat source model has been adopoted to deal with simulation of laser welding temperature field. Temperature field distribution has been analyzed and the range of suitable welding parameters has been defined.The fiber laser beam welding of 6061 aluminum alloys has been performed. The influence of laser power, weld speed, defocus and gas flow rate on weld formability have been studied by autogenous laser welding.In the meanwhile,the microstructure and mechanical characteristics of the welded joints have been evaluated. Results showed that optimizing the laser power 2 500 W,welding speed 50 mm/s, defocus-1 mm,protection gas flow 10L/min; The grains of welded joints are tiny and usually exist as dendritic grains. There are typical columnar crystals near the edge of weld and the dendritic Al-Si eutectic lie in the weld center. The smaller line energy, the greater the hardness and tensile strength of welded joints. With optimizing laser welding parameters, the tensile strength coefficient of the joints reaching 71% of parent metal.In order to improve laser welding process of 6061 aluminum alloy,the powder presetting process has been adopted to the laser welding.The influence of different powder on weld formability, microstructure, and hardness has been studied. Results showed that mixed powder is the best program, and the composition of the mixed powder is Al:Si:Ni=8:1:1. With optimizing powder,the tensile strength of the joints reaching 246.8 MPa, the strength coefficient reaches 80% of parent metal.