Effects of oxide activating flux on laser welding of magnesium alloy

The behaviours of laser welding wrought magnesium AZ31B alloy with oxide activating fluxes (TiO2, SiO2 and Cr2O3) were studied in the present paper. The results showed that the three fluxes all can increase the weld penetration of the laser welding. A larger grain size was exhibited in the weld metal prepared with flux than that in the fusion zone prepared without flux by optical microscopy. Oxide particles were found in the weld metal by electron probe microanalysis (EPMA), when flux was used. The results of tensile tests showed that weld metal without flux has nearly 90% of base metal strength when compared to the ones with flux. The mixed mode fracture was showed in the weld with flux. The main mechanism for the increases in penetration was that the flux coat absorbed more laser energy during the early period of laser action.