Journal of Welding Science

In this research, the ultrafine-grained (UFG) composite of AA2024 and AA5083 aluminum alloys was made by accumulative roll bonding (ARB) process and butt-welded by friction stir welding. Friction stir welding (FSW) is the best method for the joining of UFG strips. Microstructural investigations were performed by optical microscope and transmission electron microscope in the stir zone (SZ), thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ). The fine recrystallized structure with a grain size of about 900 nm was determined in the weldment. Due to the strengthening mechanisms of grain boundaries, nano-meter size precipitates and solid solution strengthening, the high strength of about 403 MPa was achieved. The presence of precipitates with homogeneous distribution in FSWed strips caused a high ductility of about 14% compared to the fabricated composite strips (6.9%). The high hardness of the SZ was caused by the formation of new equiaxed grains and fine precipitates, and also the decrease in the hardness of the HAZ was due to the dissolution and coarsening of T-phase precipitates.