Experimental Study On The Friction Pull Plug Welding Of Aerospace Aluminum Alloy And Its TIG Weld

Friction pull plug welding(FPPW)is a solid-phase friction repair welding technology,mainly used for the repair of weld defects and the elimination of keyhole produced in friction stir welding.In this paper,the FPPW welds of 5A06 aluminum alloy were studied,and the geometric parameters and welding parameters of the 5A06 aluminum alloy FPPW were optimized.What's more,the FPPW of TIG welded 2219 aluminum alloy was also studied.Experiments verified the feasibility of the FPPW for the repair of the fusion weld.And the microstructure and mechanical properties of the joints were analyzed.The geometric parameters of the 5A06 aluminum alloy FPPW were optimized.Different structures of the plug were designed for testing.It has been found that the plug with a small radius of the arc surface is more likely to obtain a defect-free welded joint.The plug with a small radius of the arc surface can better restrict the upper end flash in the forging stage,and ensure the combination of the upper end of the joint.The welding parameters of 5A06 aluminum alloy FPPW were optimized,and the welding parameters included axial loading rate,axial welding force and axial feeding displacement.Results showed that the defect-free joints were obtained with the axial loading rate of 15 k N/s-20 k N/s,the axial welding force of 20 k N-30 k N and the axial feed displacement of 6-7 mm.The mechanical properties of the joints under different parameters were also studied.Under reasonable welding parameters ranges,the joints with greater mechanical properties were obtained when faster axial loading rate,higher axial welding force and larger axial feeding displacement were used.The microstructure and mechanical properties of the 5A06 FPPW joints were analyzed.Results showed that the microstructure of 5A06 aluminum alloy FPPW joint is divided into base material(BM),heat affected zone(HAZ),thermo-mechanically affected zone(TMAZ),recrystallized zone(RZ),and plug metal(PM).The second phase of TMAZ redistributed due to plastic deformation,which is the weakest region of the joint.The hardness value is 92.3 HV,and the initiation of the crack also occurs here.The FPPW of 2219 aluminum alloy TIG weld was carried out under the foundation of 5A06 plate FPPW.Through the optimization of welding parameter,the defect-free FPPW joints of fusion weld were successfully obtained.and it verified the feasibility of the FPPW for the fusion weld.The microstructure of the joint was composed of TIG weld zone(TIG),heat affected zone(HAZ),thermo-mechanically affected zone(TMAZ)and plug zone(PM).The tensile test of the specimens showed that the joint strength was about 237 MPa,accounting for 89.3% of the TIG weld,and the elongation was 3.79%,which was equivalent to the elongation of the TIG weld.