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The present work studies the effect of microstructure and precipitate formation on mechanical and corrosion characteristics of friction stir processed AA6061 alloy using different cooling technologies (cryogenic and water cooling). The results revealed that recrystallized fine grains formed in all friction stir processing samples (grain size within a range of 2–6 µm) as a result of dynamic recovery and recrystallization, while samples processed in cooling-assisted friction stir processing resulted in better grain refinement in the stir zone than in air-cooled friction stir processing. Three kinds of precipitates (Fe-based needle-shaped precipitates, Si-based round-shaped precipitates, and chain of small round-shaped Si-based precipitates) were identified in base material and friction stir processing samples. Compared to air-cooled friction stir processing, in cooling-assisted friction stir processing, the hardness and tensile strength increased but remained lower than for the base alloy due to the presence of high density Fe-based needle-shaped precipitates. The ductility after friction stir processing greatly improved due to thermal softening and dissolution of precipitates. The corrosion results demonstrated that the corrosion resistance greatly enhanced after friction stir processing due to uniform distribution of grain structure and discontinuous chain of small round-shaped Si-based precipitates in stir zone. Moreover, cooling-assisted friction stir processing resulted in improved corrosion resistance compared to air-cooled friction stir processing due to the formation of fine precipitates.

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In the current study, a wide-area stir region was created in Al5083 aluminum alloy using multi-pass friction stir processing (FSP) with 50% pin overlapping. Microstructural investigations such as grain structure analysis and intermetallic particle (IMPs) distribution were carried out on processed alloys using optical and scanning electron microscopy (SEM). Recrystallized fine grains were developed after FSP due to the intense plastic straining and dynamic recrystallization. It was also identified that the grain refinement was uniform in the stir region of all overlapping passes, resulting in uniform hardness over the wide-area stir region. Three different types of IMPs, such as needle shape iron-based IMPs, round shape magnesium-based IMPs, and the very fine magnesium-based IMPs along the grain boundaries, were identified from the SEM analysis. The tensile test findings showed that the elongation improved drastically after overlapping FSP, while the hardness and tensile strength were found to be decreased due to high temperature thermal cycles. Electrochemical investigations revealed that the corrosion rate decreased after FSP due to the formation of uniform grain structure and dissolution of iron-based IMPs.

Herein, a large‐area stir zone (SZ) is fabricated in AA2014 alloy via overlapping friction stir processing (FSP). The microstructure and texture evolution of AA2014 alloy during FSP is examined using electron backscattered diffraction (EBSD). EBSD maps reveal recrystallized fine grains with high‐angle grain boundaries in SZ due to dynamic recovery (DRV) and continuous dynamic recrystallization (C‐DRX). Severe plastic straining induced by the tool leads to the formation of the A‐(110) <111> component. The texture component is further investigated with X‐ray analysis, and the results are reported. Mechanical testing reveals that ductility significantly increases after FSP, whereas the hardness and strength remain lower than that of base metal (BM) due to thermal softening. Corrosion studies show that the corrosion attack is significantly controlled after FSP due to the development of a homogeneous fine‐grained structure and uniformly distributed fine precipitates.