The tunnel defects were prepared through process tests on 6005A-T6 hollow aluminum profiles

and metallographic

hardness and tensile tests were carried out. After stretching

the fracture was scanned to study the effects of different size defects on the mechanical properties and microstructure of 6005A-T6 hollow aluminum profiles. The test results show that the tensile strength of the joint is negatively correlated with the tunnel size in the thickness direction. The SEM scan results show that there are a large number of equiaxed dimples at the center and edge of the tensile fracture

all of which are ductile fractures; the tunnel defects are all located in the lower part of the weld nugget on the forward side

the weld nugget zone and the vicinity of the tunnel are subjected to strong mechanical stirring

and a dynamic recrystallization process occurs

all of which are fine equiaxed crystals. The microstructure of the heat-affected zone is not much different from that of the base metal

and the grains in these two zones are elongated in the rolling direction of the profile; there are softening zones on the forward and backward sides

and due to heat-mechanical action

the minimum hardness value of the backward side is 63.6 HV

the minimum hardness value of the forward side is 84 HV.