| With the emergence of modern lasers with higher beam quality and laser power, laser welding has become an important application way of aluminum alloy welding technology. The laser reflectivity of aluminum alloy is high, which leads to low energy utilization rate. The rapid heating and cooling characteristics of laser welding could easily produce joint cracking, joint softening and numerous weld porosities. These problems greatly hinder the popularization and application of aluminum alloy laser welding.In order to solve the diffcult problems in the laser welding of aluminum alloy, the thesis builts the experimental platform equipped with a high speed camera system for the fiber laser-arc hybrid welding of aluminum alloy, to carry out the experimental study of the 4 mm thick 5A06 aluminium alloy.(1) The concepts, the classifications, the characteristics and the development prospects of laser welding and laser-arc hybrid welding are briefly introduced, as the research status of the two welding methods at home and abroad is presented, too. The thesis builts the experimental platform equipped with a high speed camera system for the fiber laser-arc hybrid welding of aluminum alloy.(2) Based on standard orthogonal test scheme and the single factor experimental method, the thesis studies the influence of five welding factors(the defocusing amount, the integrative arc welding factors, the laser power, and the laser-arc distance) on the surface forming qualities in hybrid welding. Good samples in the laser-arc hybrid welding of aluminum alloy are obtained, the microstructure, the microhardness and the tensile properties of the welded joints are analyzed.(3) Based on standard orthogonal test scheme, the thesis sutdies the porosity characteristics of the fiber laser-MIG arc hybrid welding of aluminum alloy, the result shows that compared with the laser welding of aluminum alloy, the stable fiber laser-MIG arc hybrid welding process could effectively decrease the hydrogen porosities and reduce the porosity diameter in the welded joints, without precise hydrogen source control or complex additional treatments under certain condition.(4) By using the high speed camera capturing system, the advantages of laser-arc hybrid welding relative to laser welding are analyzed from the aspects of the molten pool and the key-hole behavior. The differences of the welding formation between two different hybrid welding styles are analyzed from the aspects of the molten pool and the droplet transfer behavior, when constant current arc is changed to the pulsed arc, and when the welding direction is changed reversly. |
