Abstract
Microstructural properties and dislocation distribution of friction stir welded joint for 2024-T4 aluminum alloy were analyzed. Dislocations were mainly distributed in the grains of WNZ, mostly existed in the form of dislocation tangles and with a large number of precipitated phases. In TMAZ, dislocations existed in the grain boundary or grain interior in the form of dislocation pile-up. The dislocation density was also higher. Some dislocations existed near the grain boundary in the form of dislocation pile-up in HAZ along with some typical AlCu3 precipitated phase. In WN and TMAZ, the number and types of dislocation were not reduced along with the grain refinement because of the dynamic recovery and dynamic recrystallization process. The dislocation distribution was inconsistent with the hardness distribution of welded joints. The dislocation formed could be roughly divided into three phases: dynamic response process, dynamic recrystallization process and continuous deformation and recrystallization process.

Key words
2024 aluminum alloy, friction stir welding, dislocations, microstructure, hardness

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