Study On Flux-assisted Laser Welding And Particle Enforced A-TIG Welding For Magnesium Alloy

As the lightest structure material, Magnesium alloys have many advantages, such as low density, high specific strength, damping capacity, better mechanical properties, recyclable and so on, which are attracting more attention from the domestic and foreign. With the wide use of magnesium alloy structure in manufacture, it is requested to investigate and apply the high-efficiency and quality welding technique of magnesium alloy. A-TIG welding of magnesium was studied previously, and results showed that applying the activating flux on the AZ31B alloy surface leads to an increase in weld penetration depth.The behaviors of laser welding wrought magnesium AZ31B alloy with activating fluxes were studied in the paper. The results showed the fluxes can increase the weld penetration of the laser welding. The effect of parameters on penetrations was studied by systemic experiments. The microstructures and mechanical properties were analyzed and compared between the welds with and without flux. The microstructures were all of typical laser welding, and the fusion line was clear, the heat affect zone was narrow. An irregular and larger grain size was exhibited in the weld metal prepared with flux than that without flux. Oxide particles were found in the weld metal when flux was used. The results of tensile tests showed that weld metal with flux was lower than that without any flux. The main mechanism for the increases of penetration was that the flux coat absorbed more laser energy during the early period of laser action.A-TIG welding of magnesium alloy was investigated, and oxide powder mixed with enforced particles was selected as the flux. The results indicated that the penetrations with different percentage of SiC in the flux were almost the same, and that they were 1.5 times than that without flux. It was showed that the SiC particles were distributed dispersed in the weld bead. The mechanical properties of the weld beads were obviously improved by tensile tests, when SiC was added in the flux TiO₂. When flux 60%TiO₂+40%SiC was used, the tensile strength of the weld bead reached 89.6% of base metal, and it was almost the same with that of the weld bead without any flux. The reason of hardening of the weld bead with SiC in the weld metal was as followed: the oxide flux changed the traditional pool flow, and the SiC particles were involved in the pool and distributed uniform in the weld metal owning to intense stir of pool. The weld metal was hardened by dispersion hardening of the SiC particles.