The non-keyhole friction stir welding was used to attain the weld without keyhole in the weld end. A model of material flow was established by the fluent software. The material flow behavior during non-keyhole friction stir welding was obtained by the numerical simulation and was verified by the cross section morphology. The experimental results about cross-section morphology show that the stir zone (SZ) is approximately drum-shaped

the thermo-mechanically affected zone is banded and distributed on both SZ sides and under the SZ

and the heat-affected zone presents a basin shape. The numerical simulation results show that the maximum flow velocity of the material is located at the outer side of the sleeve

the material inside the sleeve flows downward under the action of centrifugal force generated by high-speed rotation. Increasing rotation velocity of tool and decreasing the welding speed can expand the high-speed flow area of the material

which is conducive to reducing the height of the kissing bond line at the root. The experimental results well agrees with numerical simulation results.