Abstract:The effects of laser beam welding process parameters such as laser power, welding speed and focal position on mechanical properties and microstructure of AZ31B magnesium alloy were studied. Nine joints were fabricated using different levels of laser power, welding speed and focal position. Tensile properties of the welded joints were evaluated and correlated with the weld zone microstructure and hardness. It is found that the joints fabricated using a laser power of 2 500 W, welding speed of 5.5 m/min and focal position of −1.5 mm yield superior tensile properties compared with the other joints. The formation of very fine grains in weld region, higher fusion zone hardness and uniformly distributed finer precipitates are the main reasons for superior tensile properties of these joints.

Key words: laser beam welding; magnesium alloy; tensile properties; laser power; welding speed; focal position