The weldability of thixo-molded Mg alloy sheets welded by using a new Fiber Laser Welding (FBLW) with different welding parameters was studied. The experimental results show that the magnesium alloys can get better welding appearance at higher welding speed (6 or 10 m/min) with 5kw laser power. Quantities of porosity defect occurred in the fusion zone, and the defect decreased with increasing the welding speed, together with narrower width of fusion zone. Furthermore, N2 is the major gas in the porosity both in the base metals and in the weld metals, while AE42 alloy includes higher content of H2 in the weld metal than AS41 alloy, which is proportional to the content in the base metal. The presence of gas inclusion in the base metal is the main factor contributing to the formation of porosity.
AC4C aluminum alloy and zinc-coated steel were friction stir lap welded, and the effect of insert depth of tool on microstructure and mechanical properties of the joints were investigated. Experimental results show that the insert depth of tool has a significant effect on mechanical properties of joints. For normal insert joints (the probe of tool does not touch the surface of steel), the joints fracture at the interface. For deep insert joints (the probe is inserted into the steel), the joints fracture at the steel base material side and the failure load is equal to that of steel base metal. The change of fracture location is attributed to the disappearance of the heavy lamellar intermetallic compounds (IMC) layer at the joining interface by the stir behavior of tool. The effect of insert depth of tool on the morphology and distribution of IMC layer was discussed.
The weldability of thixo-molded AS41 Mg alloy sheets welded by using Friction Stir Welding (FSW) under different welding conditions was studied. The appropriate FSW condition range of several kinds of Mg alloys is given, and it seems that the appropriate FSW condition range increases with decreasing the Al content in the Mg alloys. Grains of base metal have been deformed greatly after friction stirring, and the hardness of SZ is higher than that of base metal. The tensile strength and elongation of all-SZ specimen of AS41 alloy increased with decreasing the welding speed and increasing the rotation speed.