According to the principle that self-pairing of the same metal could increase the friction coefficient

friction flow welding was conducted on 6061-T6 aluminum alloy by using improved pinless friction stirring tool.Tensile fracture mechanism of the weld was analyzed using macro-morphology analysis and tensile testing.The results show that embedding the material to be welded in form of bar into the friction stir tool can increase friction and adhesion between the friction stir tool and the workpiece

thereby increasing thickness of the plastic zone of the weld.The larger the diameter of the bar embedded into the friction stir tool

the higher the soldering temperature-increment rise rate.When diameter of the bar reaches 10 mm

tensile strength of the weld reach up to 250MPa（86% of the base material）

which is1.8times of the sample welded with ordinary friction stir tool.