| The weldability,easy processing and corrosion resistance is the characteristics of Al-Mg-Si aluminum alloy.It is widely used in aviation,aerospace and other industries pursuing lightweight development.During the welding process,the alloy elements inside the aluminum alloy are prone to burn,and the welded joints have defects such as pores and cracks,which is not conducive to the wide use of Al-Mg-Si alloy.In this paper,the GTAW welding arc of magnetically controlled 6061 aluminum alloy is taken as the research object,and the numerical model of GTAW welding arc of 6061 aluminum alloy is established based on magnetohydrodynamics.The arc characteristics of GTAW welding aluminum alloy before and after external magnetic field are simulated.The characteristics of welding arc and welding pool under different simulation parameters are explored.Combined with analysis of welding experimental,the influence of external magnetic field on TIG welding of aluminum alloy is deeply understood,and its mechanism is analyzed.The characteristics of arc plasma are different and the maximum arc temperature is different when the polarity of alternating current changes without magnetic field.In the positive polarity range,the arc temperature field is symmetrically distributed,and its cross section is circular.At 100 A current,the maximum temperature is 14 862.4 K and the maximum speed of arc plasma is 27.6 m/s.The influence on arc voltage in the workplace is concentric.The maximum current density is at the tungsten extreme,and the maximum current density is 2.66×10~7A/m~2 in the arc region,the potential changes dramatically.The existence of cathode spots makes the current densities on the surface of the workpiece slightly increase,changing to 8.25×10~6A/m~2,which is smaller than that at the extreme part of tungsten.Lorentz force in the extreme part of tungsten reaches 1.21×10~5 N,which is related to the arc current density.Under the action of pulse power supply with the same peak and base currents but different duty cycles,the maximum temperature of the arc does not change.At the rise and fall edges of the current,the characteristics of the arc plasma transformation are different.The welding arc deflects after the transverse magnetic field is applied.The temperature field section of the arc gradually transits to the ellipse,and the welding arc has similar characteristics with the moving arc.Comparing the arc characteristics under the applied magnetic field intensities of 0 m T,0.1 m T and0.2 m T,it is found that the Lorentz force inside the arc gradually increases to1.51×10~5N,when the magnetic field intensity is 0.2 m T,and the welding arc plasma velocity and arc pressure increase.At the same time,the deflection of the arc leads to the arc length increase and the extension of arc plasma path,and the arc pressure acting on the workpiece surface decreases.Under different magnetic field intensities,the arc potential increases,and the potential gradually increases from 8.67 V to 8.78 V and 8.96 V.The deflection of the welding arc also leads to the change of the temperature field distribution of the workpiece after the transverse magnetic field is applied.After the deflection of the arc,the high temperature region is farther from the workpiece.The maximum temperature on the workpiece gradually decreases with the change of the high temperature region,which is 2390.0 K,2 378.4 K and 2 358.1 K respectively under different magnetic field intensities,and the maximum temperature region is no longer directly below the tungsten electrode.Compared with the TIG welding experimental results of 6061 aluminum alloy with the same process parameters,the simulation results of temperature field distribution are consistent with the experimental results.The microstructure and XRD analysis of the welded joint samples were carried out.The results show that the grains of the welded joint of 6061aluminum alloy are refined after the external magnetic field,and the internal phase of the alloy joint is mainlyα-Al phase. |
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