Microstructure and properties of 6061-T6 aluminum alloy joint welded with ZL101 A welding wire by MIG after and before solid solution and aging treatment were investigated by optical microscope（OM）

scanning electron microscope（SEM）and computer-controlled electronic universal testing machine.The results show that there exist only three zones including matrix

fusion and welded zone.Mg2 Si strengthening phases and incomplete fusion phases are decreased in the matrix

however

Mg2 Si strengthening phases with increase and uniform distribution can be precipitated at the grain boundary and grain interior in the welded zone during aging treatment.The welding joints have the higher tensile strength and elongation in the weld zone

reaching 293.3 MPa and 6.8%

which are 94.6% and 56.7%of the base metal

respectively

so it is cracked at the welded zone.On the contrary

the untreated welding joints are cracked at the heat affected zone.Welded joints before and after treatment are characterized by typical ductile fracture.