Effect of Post-weld Heat Treatment on Microstructure and Properties of 6061 Aluminum Alloy Laser-Welded Joints

The effect of post-weld heat treatment process on the microstructure and properties of 6061 aluminum alloy joints welded using ER4047 wire by laser welding was studied by optical microscope, scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). The research results indicated that with the increase in annealing temperature, the grain size of the weld seam showed a certain degree of coarsening. Moreover, some low-angle grain boundaries gradually transformed into high-angle grain boundaries, the preferred orientation weakened gradually, and there was a distinct texture evolution path of Goss+{102}<201> + Cube -> Brass-R{236} <384> + {114} <234> + R-{124} <211> -> Goss-Brass + {110} <411>. Additionally, the elimination of welding residual stress, the increase of low Sigma CSL grain boundary proportion and beta-Mg2Si precipitations significantly improved the mechanical and corrosion resistance properties of the joints. Among which, the joint exhibited the best comprehensive performance after annealing treatment at 200 degrees C for 8 h.