Effect of natural aging on microstructure and properties of fiber laser-VPTIG hybrid welding of A7N01 aluminum alloy

The influence of natural aging on joint microstructure and mechanical properties of fiber laser-variable polarity TIG hybrid welding of 4 mm thick A7N01 Aluminum Alloy was investigation by OM, DSC, TEM analysis and mechanical properties test. The experiment results show that the joint mechanical properties was significantly improved and achieved stability after natural aging of 30 days, and the joint average tensile strength was 369 MPa, which is equivalent to 83% of base metal. The tensile strength was increased by about 15% more than that of as-welded joint and the elongation was increased from 3.1% to 4.4%. For the joint of natural aging of 60 days, the tensile strength was increased to 394 MPa by removed the reinforcement, achieve the 94% of that of base metal, and the elongation was achieved to 7.6%. The tensile fracture occurred in the fusion zone, and the fracture morphology was distinctly ductile characteristics. After natural aging, the joint microstructure did not significantly change, but the number and the size of precipitated phase was increased. The precipitation were mainly GP zone and little ofη' orηphase. The precipitated phase can improve the strength of welded joint by pinning dislocations.