Research Of CMT Welding Performance Of Aluminum Alloy

Aluminum and aluminum alloy have excellent properties and they are applied widely in multi-domain,so the high-quality welding of aluminum alloy structure has important significance.The traditional welding methods of aluminum alloy are TIG welding and MIG welding.These welding techniques are relatively mature.But they also have their own shortcomings,for example,TIG welding is low production efficiency,the carrying capacity of the tungsten electrode is poor and easy to attach tungsten in the weld metal.There are welding defects such as cracks,pores,incomplete fusion,lack of penetration and welding deformation in MIG welding.Cold metal transition welding(CMT)technology has the advantages of low welding heat input,no splash,it is suitable for the welding of aluminum alloys.But CMT welding technology is facing the market in recent years,therefore,the welding process and welding properties need to be further studied.In the thesis,1060 aluminum alloy and 6082-T6 aluminum alloy with 2mm thickness were used as the test materials,the filling materials were ER1100 pure aluminum wire and ER4043 aluminum silicon wire with diameter of 1.2mm.The optimum process parameters were determined by optimizing the process parameters.The weld formation,microstructure and phase composition of weld were studied by metallographic microscope(OM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD).The hardness distribution of welded joint was measured by micro vickers hardness tester,the tensile properties of welded joint was measured by universal tensile testing machine.The results showed that the optimum process parameters for CMT welding of 1060 aluminum alloy which the welding current was 90 A,the welding speed was 110cm/min and the arc-length correction coefficients was 0%.Under the optimum process parameters,the weld formation was beautiful.The microstructure of 1060 aluminum alloy CMT weld metal was mainly composed of ?-Al solid solution.The morphology of the crystals was mainly columnar crystal growth from the fusion line to the weld center.The hardness of weld metal was about 28-30 HV,the hardness of heat affected zone was about 27-32 HV,and the hardness of base metal was about 36-39 HV.The tensile strength of the tensile specimen was about64.45 MPa,which the tensile strength(87MPa)of the base metal was 70%,the elongation was4.77%,the fracture location was in the heat affected zone,the fracture morphology was plastic fracture.The optimum process parameters for CMT welding of 6082-T6 aluminum alloy,which the welding current was 105 A,the welding speed was 110cm/min and the arc-length correction coefficients was 0%.Under the optimum process parameters,the front of the weld was evenly formed,the back of the weld was welded and the weld was well shaped.The microstructure of 6082-T6 aluminum alloy CMT weld metal was mainly composed of ?-Al solid solution and a small amount of Mg2 Si intermetallic.The crystalline morphology of ?-Al solid solution was composed of cell crystal,columnar crystal,equiaxed crystal from the fusion line to the weld center.The hardness of weld metal was about 65-73 HV,the hardness of heat affected zone was about 60-95 HV,and the hardness of base metal was about 95-98 HV.The tensile strength of the tensile specimen was 188.52 MPa,which the tensile strength(310.24MPa)of the base metal was 61%.The elongation was about 4.77%,the fracture location was in the heat affected zone and the fracture morphology was plastic fracture.