Study Of EBW Processes Of2219Aluminum Alloy And Performance And Mechanism Of Welded Joints

As a result of its characteristics of good mechanical properties at low and high temperatures,good fracture toughness and weld-ability and corrosion resistance,2219aluminum has been widelyused in the aerospace especially in the area tank. With the rapid advances in industrial productiontechnology and the requirement for enhancement of the quality of the aircraft structure, people areincreasingly concerned about the performance of2219aluminum welded joints. In this paper2219-T6aluminum alloy plates of6mm-thcikness are electron beam welded, studying the electron beamwelding process and the performance and mechanism of different welded joints of2219-T6aluminumcombined with the TIG and FSW welded joints of2219-T6aluminum alloy, so as to lay thefoundation for2219-T6aluminum applications in industrial production.The experiment results of electron beam welding process demonstrate that the room temperaturetensile and impact properties of electron beam welded joints of2219-T6aluminum share the same lawof variation, and the welding parameters have an optimum adaptation. Within this adaptation, themaximum tensile strength is332MPa, at the same time the maximum elongation is6%; the maximumimpact toughness is35J/cm2.Investigating the performance characteristics of the three welded joints, the results demonstratethat the maximum of the room temperature tensile is electron beam welded joints of2219-T6aluminum, which is80%of that of the base metal; the followed is friction stir welded joints, which is74.04%of that of the base metal; the smallest is TIG welded joints, which is55.29%of that of thebase metal. The fracture location in the room temperature tensile of the TIG, FSW and EBW weldedjoints were respectively at weld center, thermal mechanically affected zone and heat affected zone atthe retreating side, and fusion zone. At the same time the impact toughness of EBW joints is good,which achieves35J/cm2(slightly lower than that of FSW joints, which achieves40.21J/cm2) and is2.07times of that of the base metal.The micro-structural analyses of the three welded joints show that the weld center of TIG jointsis composed of equiaxed branch grains while α（Al）-Al2Cu eutectic unevenly distributed between theinter-granular and branches, but weld center of the FSW and EBW joints is composed of fineequiaxed grains. The different grain size of the three welded joints is one of factors but not the mostimportant. There are some porosity defects in TIG weld zone, little small and difficult to detectdefects in FSW weld thermal mechanically affected zone at the retreating side, and few extremely small porosity defects in EBW weld zone. XRD results show that the weld zones of the three weldedjoints is composed by α-Al matrix, in addition Al2Cu strengthening phase is also found. Followed bySEM, TEM observation shows that network-like precipitates form in the grain boundaries in the TIGweld zone between the welding process; the precipitates in the weld center of FSW and EBW jointsare showing granular. The overall size of precipitates in weld center of FSW joints is large and notuniform, but that in weld center of EBW joints is small and evenly distributed. The precipitates inweld center of EBW joints show the largest contribution to the intensity by comparison. Therefore, thesize and distribution of precipitates in the weld center of three welded joints is the main factor whichlead to differences in intensity, and it determines the performance of welded joints with size of grainand welded defects.The corrosion test results of the three welded joints reveal that the surfaces of FSW and EBWjoints only appear a small amount of pitting corrosion pits after immersion corrosion, but the surfaceof TIG joints appears the most of pitting corrosion pits and pitting corrosion pits in TIG joints surfaceeven interconnect strips. The corrosion current of the EBW joints is1.736×10-5A, and charge-transferresistance is5.015×103·cm2, they slightly lower than that of FSW joints but significantly better thanthat of BM and TIG joints by comparison. In summary, the corrosion performance of the FSW andEBW joints are better than that of BM and TIG joints.