Research On Technology And Microstructures And Mechanical Properties Of Fiber Laser Welded5083Aluminum Alloy

5083aluminum alloy is a typical of Al–Mg series alloy, and it has a greatpotential to be used as structural material in ship-building industry and also inautomotive and aerospace industry due to its excellent combination of strength,corrosion resistance and weldability. The common problem of this alloys’ weldabilityis high deformation and low efficiency when using the traditional arc welding method.Now, advanced laser welding process can solve the problem of large deformation incomponents’ joining. However, there are a number of problems need to overcome,just like instability of the welding process and defects such as sag, undercut andporosity. And all this problems are caused by keyhole’s dramatic eruptions and strongfluctuations in molten pool during laser deep penetration welding process. Somestudies have shown that adjusting process parameters can improve weld quality.Therefore, the purposes of this paper are finding process’ rules of high power fiberlaser welding, optimizing welding parameters and also analyzing on characteristics ofmicrostructure and mechanical properties of welded joints.Autogenously bead-on-plate fiber laser welding has been presented on5083aluminum alloy,4mm thick. The results show that pores can be avoided under theconditions of deep penetration process. High power and high speed will make the bestchoice of inhibiting sag and undercut. Microstructure of the weld consists of bothcolumnar crystals growth along the base metal and isometric dendrites rely onheterogeneous nucleation in the weld center. And the whole weld consists of twotypes of phases, solid solution shaped like column or branch and amorphous locatedin the grain boundary. Tensile strength of joint is up to287MPa, about83.9%ofparent material. Yield strength is about227MPa. Elongation is about3.57%. Thetensile fracture is happened in weld, and is belong to ductile fracture.Laser beam welding with filler wire5087shows that a joint with well formedand non-defects can be obtained by optimizing the parameters. But the well range isnarrow and need strictly controlling the technological conditions. Among this study,Influence of parameters on weld formation has been analyzed in details. Filler wireintroduces more nucleation particles and causes uneven distribution of elements in theweld. Metallographic analysis indicates that internal grain in the welds has beensignificantly refined. And it also indicates that weld has shown dendritic segregation and layered segregation phenomena. The average tensile strength of joint with fillerwire is304MPa, which improved6.17%compared with autogenously welding.Elongation is about5.43%, and improves52%. The average yield strength is226MPa,pretty close with base metal and autogenously joint. It indicates that the main factoraffecting the mechanical property is weld defects, including sag and undercuts.Precipitates in the grain boundary of the weld have been studied in this paper. Itcan be determined that phase structure of the precipitates is non-crystalline, becauseof its chaotic atomic structure showing under the high resolution electron microscopic.The composition of amorphous phase in weld has been counted and tested in asemi-quantitative way. The results show that amorphous phase precipitates are mainlyformed in Al-Mg-Si-O, with or without other trace elements included Mn, Fe, Cu, Cr.Therefore, this type of alloy system has a large amorphous forming ability.