Effect of temperature alternating load on stripping performance of Al-Li alloy T-joint manufactured by dual laser beam bilateral synchronous welding

In this work, the temperature alternating load (TAL) with four cycles is performed to the 5A90 Al-Li alloy T-joint produced by dual laser beam bilateral synchronous welding (DLBSW). The grain details, stripping strength, fracture micro-morphology and elemental composition of the samples are analyzed by optical microscope, self-designed specific fixture, scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS), respectively. The experiment results indicate that the TAL treatment has a slight decrease on the width of non-dendritic equiaxed zone (EQZ) near the fusion line. The average striping strength and post-break elongation of the TAL treated samples are separately 126.01 MPa and 3.60%, which are both reduced compared with the values 145.61 MPa and 5.54% of the untreated samples. Meanwhile, the results of fracture micro-morphology and elemental composition are utilized to investigate the decline of the tensile performance of the T-joint with the TAL treatment. It is found that the fracture features such as tear layers, shear dimples and torn pores are relatively insignificant compared to the T-joint without the TAL treatment. The non-uniformity of element distribution exists in the TAL treated and untreated sample.