Influence of Post-Weld Heat Treatments on Microstructure and Mechanical Properties of Laser Beam Welded 2060-T3/2099-T3Al-Li T-Joints

Abstract

The durable structure and robustness of T-joints in the panel materials for civil aircraft are a crucial matter of importance. In this work, the impact of the post-weld heat treatments (PWHTs) on the microstructure and mechanical properties of laser beam welded T-joints of 2060-T3/2099-T3 Al-Li alloy was analyzed. Heat-treatment of the laser beam welded T-joints was carried out in two different ways, namely, solution treatment and artificial aging (STAA) at varied duration and only artificial aging (AA) at varied duration. The microstructure and mechanical properties of the heat-treated joints were investigated using metallographic and scanning electron microscopic images, micro-hardness test, and tensile test, respectively. The results showed that, in cases of STAA, the eutectic structures on the grain boundary were partially dissolved via solution treatment (ST), and increased dispersed precipitation of the second phase in matrix resulted in significant dispersion strengthening, as well as enhanced strength and plasticity. In contrast, in the AA process, alloy elements in the matrix continued to segregate towards the grain boundary, resulting in significant grain boundary strengthening, enhanced strength, and decreased plasticity. Additionally, joint fractures were micro-porous aggregation transgranular ones in the fusion zone (FZ). The joints treated by STAA exhibited excellent plasticity compared with those treated by AA. Furthermore, the micro-hardness of welded joints treated by AA was higher than that of those treated by STAA. Indeed, the tensile strength of joints treated by STAA and AA ranged from 405 to 475 MPa, which was 81–95% of the base metal 2060-T8, though the elongation of joints treated by STAA was superior to the counterpart AA.

Effect on the Property of 2195 Al-Li Alloy Laser-Welded Joints with Different Filler Materials

“…Nowadays, microstructure evolution, mechanical properties, softening, and hotcracking sensitivity of laser-beam-welded joints were studied [10]. In order to improve the performance of the T-joint, Zhang [11] carried out two different post-weld heat treatments, namely solution treatment and artificial aging (STAA) and artificial aging (AA). In the case of STAA, the increased second phase in the matrix resulted in significant dispersion strengthening and enhanced strength.…”