Abstract: Using the aluminum foil as a tracer material,friction stir welding was conducted with different process parameters.The effect of rotating velocity,welding speed and plunge depth on the weld transverse section morphology was studied.The results showed that the metal flow in the weld was composed of four characteristic zones,i.e.,flow zone,turbulence zone,onion zone and rigid plastic transfer zone.The weld was unsymmetric about the center line,and the deformed intensity of the tracer material on the retreating side (RS) was higher than that on the advancing side(AS).With the increase of the rotating velocity,the highest upward displacement of the metal in weld thickness initially increased and then decreased.With the increase of the welding speed,the highest upward displacement of the metal decreased.It was favorable for metal flow and improvement of compactness of the weld with the increase of plunge depth of the tool.