Effect of post-weld heat treatment on the microstructure, phase composition and mechanical properties of dissimilar Al-Mg-Li/Al-Cu-Li laser welded joints

•High-strength laser dissimilar welded joints of aluminum–lithium alloys were obtained.•The post-heat treatment of the weld has been optimized to obtain maximum mechanical properties.•Quenching formed δ′(Al3Li) in the weld. Artificial aging led to T1(Al2CuLi) formation and increased δ′(Al3Li) content.•After PWHT, joint showed properties, similar to Al-Mg-Li alloy: 411 MPa ultimate strength, 327 MPa yield, 1.7 % elongation.