Effect of post-weld heat treatment on microstructure and mechanical properties of laser welded 7075Al alloy

7075 high-strength aluminum alloy joints were prepared by laser self-fusion welding technology, and the effect of post-heat treatment on the microstructure and tensile properties of the joints was studied. The microstructure evolution and tensile fracture behavior of 7075 joints after post-heat treatment were characterized by SEM and EBSD systems. The results show that there are equiaxed grain regions, columnar grain regions, cellular grain regions and base metal as-rolled regions from the center of the weld to the base metal. The cellular and equiaxed grain regions are weak areas of the joint. Compared with the unheat-treated joint, the average tensile strength of the post-heat-treated joint reached 475 MPa, an increase of about 59%. The nano-precipitated phase constructed by the post-heat treatment triggered the second-phase strengthening mechanism, which was the main factor to improve the tensile strength of the joint.