| Outstanding day different of the world’s energy problems, Use magnesium,aluminum, titanium and other new type lightweight materials to replace traditional steelmaterials can reduce energy consumption effectively. Due to the characteristics of thelight metal and its alloys are mostly poor weldability, Currently, a large number ofstudies have focused on how to improve the microstructure structure and improve themechanical properties of welded joints. Magnesium alloy as the21st century greenengineering materials, the applications as well as the industrialization process ofMagnesium alloy welding will be taken seriously.In order to improve the quality of welding of magnesium alloy and improvewelding productivity, and expand its scope of application, this issue studied TIG andA-TIG welding process of AZ31magnesium alloy. The experiment optimized processparameters of3mm thick AZ31magnesium alloy plate automatic feed wire TIGwelding; developed compound flux for a new type wire, studied the impact of newcomposite flux to macro-organization, microstructure and properties of AZ31magnesium alloy A-TIG weld; analyzed the mechanism of the composite flux increaseweld penetration and improve the weld pool morphology. Apply metallographicanalysis, scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS）,X-ray diffraction （XRD）, micro-hardness testing method etc. to study obtained weldedjoints. The results obtained are as follows:①The role of the compound flux made AZ31magnesium alloy A-TIG weldedjoints in a smaller current to be penetration and the welding heat to be reduced, thewelding thermal cycle was optimized and the weld organizations can be refined.②In the welding of AZ31magnesium alloy, coating amount of flux is too low willaffect the increasing weld penetration result, while the coating too much will affect theformability of the welding, in the coating amount of per unit area was8.3±0.5mg/cm2,the effectiveness of weld penetration increasing and quality of welding were ideal.③In this study, detected AZ31magnesium alloy TIG and A-TIG welded joints,study found that molten flux covering the pool surface to protect the pool, the protectivelayer can lower metal activity which will evaporate out of the pool. Therefore, reducedevaporation and burning of metal, made A-TIG element migration diffusion than TIGwas more stable and weakened elements segregation phenomenon. ④In A-TIG welding process of AZ31magnesium alloy, The compound flux acted" the arc contraction "and" surface tension "composite mechanism to increase the weldpenetration. NaCl and KCl caused arc contraction, NaF and LiCl changed the surfacetensions of weld pool.⑤The amount of second phase β-Mg17Al12in the A-TIG weld of AZ31magnesium alloy was higher than that in the TIG weld. The β-Mg17Al12which wasdistribution of continuous mesh increased the hardness value of the joint and improve dthe mechanical properties of welded joints.⑥AZ31magnesium alloy A-TIG joints tensile strength higher that of TIG weldedjoint, fracture location of the A-TIG joints were away from the center of the weld at4-5mm, TIG joints fracture location were near the center of the weld, fracture modes ofjoints both were brittle fracture. |
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