Microstructure evolution and mechanical property of laser welded Al-Li alloy with filler strip

Abstract

Al-Li alloy has excellent specific strength and corrosion resistance, which shows a wide application prospect. However, its further application is hindered by the high crack sensitivity. In this work, the 2195 Al-Li alloy sheet filled with strips was welded by pulsed laser. The results showed that the weld joint with nearly no cracks was obtained after the filling of strips. The temperature gradient and cooling speed of the molten pool were reduced by nearly 50% and 42%, respectively. The Cu was segregated at the grain boundaries of the weld joint. The eutectics of the weld were T1-Al2CuLi and T2-AL6Cu (Li, Mg)3 phases. The combination of element segregation and the reduction of the strengthening phases in the weld joint were the main reasons for the decrease of the mechanical properties. The tensile strength of the weld joint could reach 310.56 ± 2.88 MPa. The weld joint was intergranular fracture, belonged to mixed fracture mode.