Study of the structure and phase composition of laser welded joints of Al-Cu-Li alloy under different heat treatment conditions

This paper explores the structure and phase composition of laser welded joints of Al-Cu-Li alloy without and after post heat treatment (annealing, quenching, and artificial aging). Changes in the structure and phase composition of welds and the base alloy before and after heat treatment are studied using scanning electron microscopy, X-ray diffractometry, and synchrotron radiation diffraction. The investigation results have shown that the formed agglomerates of intermetallic particles are mainly represented by the T-1(Al2CuLi) phase. The change in the strength of the Al-Cu-Li alloy samples after laser welding and heat treatment is not due to the absence or presence of the strengthening T-1(Al2CuLi) intermetallic phase but rather due to the different localization of particles of this phase in the weld joint. The segregation of the phase at dendritic grain boundaries leads to a significant strength decrease, and, vice versa, its homogeneous distribution in the solid solution achieved by post heat treatment (annealing, quenching, and artificial aging) increases the strength of the laser welded samples.