Investigation On High-Efficiency Hybrid Welding Process Of Aluminum Alloy And Microstructure And Properties Of Welded Joint

In this thesis,laser-MIG hybrid welding,filling wire plasma arc welding,and plasma-MIG hybrid welding experiments were carried out on aluminum alloy.The influence of process parameters on the formation of welds was studied.The microstructure distribution of joints was analyzed and the mechanical properties of joints was tested.During the experiment of 6 mm thick 7N01 aluminum alloy laser-MIG hybrid welding,the influence of laser power,wire feeding speed and groove angle and gap on the weld formation were studied under two methods of injecting shielding gas at the bottom and forced forming.It was found that when the laser power reached 3.0 k W,the workpiece was well penetrated.As the wire feeding speed gradually increased within a reasonable range,the holes in the joint were significantly reduced.When the groove angle was 60°and the wire feeding speed was 8.0 m/min,the holes were minimal.By using this process parameter,the hardness of the weld zone was 85.8 HV_0.5,which was 75.3%of the base material,the tensile strength of the joint was 285 MPa,and the strength coefficient was 63.3%of the base material.In the experiment of 5 mm thick 5083 aluminum alloy filling wire plasma arc welding,the effects of plasma current,wire feeding speed and welding speed on weld formation were studied.When the wire feeding speed was 5.5 m/min,the plasma current was 220 A and the welding speed was 40 cm/min,the weld was well-formed by using"I"-shaped groove and the plate gap of 1.2 mm.The hardness of the weld zone was 66.4 HV_0.5,which was 89.7%of the base metal.The tensile strength of the welded joint reached 308 MPa,and the strength coefficient was 88%of the base metal.During the experiment of 6 mm thick 7N01 aluminum alloy plasma-MIG hybrid welding,the effects of MIG voltage,wire feeding speed and plasma current on weld formation were studied.Two methods that the"I"-shaped groove without a gap and the"Y"-shaped groove with a gap of 1.2 mm were used to find suitable process parameters.It was found that for the"I"-shaped groove,the better process parameter were that MIG voltage was 21V,the plasma current was 170 A and the wire feed speed was 10.0 m/min,for the"Y"-shaped groove,the better process parameter were that MIG voltage was 21V,Plasma current was 160 A and wire feeding speed was 10.0 m/min.By the better process parameters,the joint of"I"-shaped groove had a higher tensile strength of 297 MPa,which was 66%of the base material,the joint of"Y"-shaped groove had a lower tensile strength of 277 MPa,and the strength was61.6%of base material.