CO₂ Laser Welding With Filler Wire Of Wrought Magnesium Alloys

As the lightest structural materials available so far, magnesium alloys have already found considerable applications in aerospace, aircraft, automotive, electronics and other fields, and welding technique has been a key technology restraining the application of magnesium alloys. laser welding will probably become an important joining technique for magnesium alloys due to the low and precise heat input, small HAZ, deep and narrow FZ, low residual stress and weldment distortion, and high welding speed. Laser welding with filler wire can expand their wider uses in industries. The system of laser welding with filler wire has been developed, and CO₂ laser welding of wrought magnesium alloys with and without filler wire were investigated in this paper.The study shows that laser power and welding speed are two important process parameters that influence the weld shape and weld width. The effect of shielding gas flow rate on weld width can be ignored, but it has a great effect on fusion zone metal. Focal position greatly influences the weld cross section shape, and focal spot was fixed on the surface of workpiece in order to obtain a higher melting efficiency. The surface condition of magnesium alloys may influence the energy absorption of incident laser beams as well as the threshold power density for keyhole welding. Sandblasting can greatly improve the effectiveness of welding. On the same processing conditions, the weld width of CO₂ laser welded AZ61 magnesium alloy is bigger than that of AZ31 magnesium alloy, so AZ61 alloys have a higher fusion efficiency.Good appearance of weld can be got using appropriate laser welding process parameters. The results of metallographic examination show that weld grains are refined, and dendritic crystals exist in the fusion zone. It was found that the microhardness and tensile strength of welded joint are higher than that of parant metal, therefore weld bead has a better mechanical properties. Filler wire addition can controll weld sag, and the weld cross-section is cup-shaped. In addition, the best wire feeding angle is between 20 and 35 degree. The...