Study on Laser Welding Process, Microstructure and Properties of AZ31B Magnesium Alloy

AZ31B magnesium alloy sheets of 4.0 mm in thickness were successfully butt-welded by using laser beam welding (LBW). The effects of laser beam welding parameters such as laser power, welding speed and focal position on microstructure revolution and mechanical properties of AZ31B magnesium alloy were investigated. The results showed that the welded joints fabricated using a laser power of 2.5 kW, welding speed of 30 mm/s and focal position of + 2 mm presented optimized macroscopic morphology and best tensile properties compared with the other joints. The formation of fine grains in weld zone and uniformly distributed fine precipitates were the main reasons for superior tensile properties of these joints. In addition, there was only α-Mg phase and no β-Mg17Al12 was observed in the weld zone. The spherical particles in the weld zone were α-Mg segregation rich in Al and Mn.