| Al-Cu high-strength cast aluminum alloy is widely used in the pursuit of lightweight development in modern manufacturing industry.However,such aluminum alloy MIG welding has poor weld forming performance,coarse crystal structure and mechanical properties of weld zone.Problems such as poorness are not conducive to the wide range of use of Al-Cu-based aluminum alloys.This paper is based on the surface welding of ZL205A aluminum alloy surface MIG welding method,and studies the effect of external alternating magnetic field on welding arc and weld formation and microstructure.The effects of alternating magnetic field on welding arc,microstructure,mechanical properties and corrosion resistance were investigated by testing the welding arc shape,weld forming quality,metallographic structure,and the mechanical and electrochemical corrosion properties of the weld.When the arc of MIG welding is subjected to an external alternating magnetic field,deflection and rotational movement occur,and as the magnetic induction intensity increases,the arc deflection phenomenon is aggravated.When the magnetic induction is too large,the arc is stable and deteriorates,and the welding process cannot be stably performed.This study found that under the condition of the existing experimental device,when the magnetic field strength is 2.2mT and the crossover frequency is 50Hz,the alternating magnetic field has a great effect on the weld performance and the welding process is stable and the spatter is less.In this paper,orthogonal test method is used to study the effect of welding process parameters on the surface weld overlay of ZL205 alloy.Through experiments,it was found that the welding current,welding speed and welding voltage during the surfacing process all affect the forming quality of the weld.The influence of welding current and welding speed is significant,and the welding speed mainly affects the surface formation of the weld,and the welding current has a great influence on the bonding quality of the weld and the base metal.The addition of alternating magnetic field has obvious effects on weld formation,including weld fish scale pattern,penetration depth,and melting width.It can be seen from the experiment that the magnetic field strength is obvious and the alternating frequency has little effect.In terms of microstructure,the addition of an alternating magnetic field promotes the formation of equiaxed crystals,and as the magnetic field strength increases,the grain size of the matrix?-Al becomes fine and dispersed,and the crystal grains of the surfacing layer become fine.At the same time,the introduction of alternating magnetic field can improve the morphology of Al2Cu phase and Al12Mn2Cu phase,so that it can be attached or even wrapped around?-Al to inhibit the growth of?-Al in the weld,which helps to improve the weld performance.Especially when the magnetic field strength is 2.2mT and the excitation frequency is50Hz,the weld microstructure is fine.At this time,the weld hardness is increased by 11.1HV and the impact toughness is increased by 14.75J/cm2 compared with the case of no external magnetic field.Compared with the base metal,the corrosion potential of the weld is increased,and the corrosion current density is greatly reduced,and the corrosion resistance is remarkably enhanced.The addition of an alternating magnetic field can cause the liquid metal to undergo a violent flow effect under the action of Lorentz force,which acts to inhibit dendrite growth,increase the number of equiaxed grains,refine grains,and reduce the formation of weld defects.It is an effective means of comprehensive performance of materials. |
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