Research on the stripping performance during dual laser-beam bilateral synchronous welding of 2219 aluminum alloy T-joint for spacecraft

Abstract

The promising dual laser-beam bilateral synchronous welding (DLBSW) technology was employed in the 2219 aluminum alloy T-joint which consisted of the skin and stringer components. The coherent weld seam (WS) is achieved under the heat affect of dual laser beam. The stripping experiment was carried out to test the stripping strength of DLBSW joint. With the purpose of discussing the relationship between the welding shape and stripping strength, H1 was measured to evaluate the shape of welded T-joint. The microstructure characteristics of T-joint were observed to discuss the crack location during striping experiment. Besides, the fracture morphology was observed by scanning electron microscope (SEM). The chemical element composition on the impure phase in the fracture was detected by energy dispersive spectrometer (EDS). The highest stripping strength is 317.46 MPa with the laser power of 5500 W and welding speed of 4.2 m/min. The stripping crack locations are mainly divided into three categories. The highest stripping strength is achieved under the second category of crack location which is taken place near the upper fusion line. It is indirectly found that the strength of WS in case 6 with the laser power of 5500 W is highest than the others. The degrading of stripping strength is mainly owing to the reducing of plasticity as well as the formation of internal defects such as pores, bonded structure and nubby impure phases. The nubby impure phase is mainly metal oxides (TiO2, Al2O3) which generally degrade the weld quality. It is notable that a new skin component accompanied with two bosses is firstly designed in the present study to replace the wire filler.