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Influence of post-weld heat treatment on microstructure and mechanical properties of laser beam welded 2195 Al–Li alloy

2195 Al–Li alloy is welded by using laser beam welding (LBW). Subsequently, the welded joints are treated by solution treatment at 520 °C for 1 h, then aging treatments with different procedures. The influence of post-weld heat treatment (PWHT) on microstructure and mechanical properties of the welded joint is systematically investigated. Optical microscope (OM), scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), and x-ray diffractometer (XRD) are used to characterize the microstructure of joints respectively. The tensile strength and microhardness of welded joints before and after PWHT are evaluated respectively. Results show that, after post-weld double aging treatment (HT3), the tensile strength of welded joint is 485.2 MPa, which is 89.03% of that of base metal. Microstructural analysis indicates that the fine equiaxed grain zone (EQZ) near fusion line disappears after HT3. The precipitation of strengthening phases such as T1(Al2CuLi) phase is promoted by PWHT both near grain boundaries and in Al matrix. Moreover, the microstructure of weldment is refined after HT3, thus the ductility of welded joint is improved to a certain extent.