In this paper

the influence of 20 mm thick 6A02 aluminum alloy double-sided friction stir process on the joint microstructure and conventional mechanical properties is analyzed

and the tensile and fatigue fracture characteristics are studied. The results show that the different lengths of the stirring needles will significantly affect the mechanical properties of 6A02 aluminum alloy double-sided friction stir welded joint.When the needle length is too short

it is easy to appear cracks in the center of the transverse lateral bending specimen of the joint. When the fatigue test fails to reach the specified number of cycles under the condition of specified cyclic load and stress ratio

fracture occurs. When the needle length matches with the pressure

the tensile

bending and fatigue test performance are good

and it is found that the tensile strength of the joint increases first and then reduces as the needle length of stirring increases.When the stirring needle length is 11 mm

the tensile strength of the joint can reach 244 MPa

which is 82.7% of the tensile strength of the base material.