Subgrain formation in ultrasonic enhanced friction stir welding of aluminium alloy

• Recrystallization in aluminium weld nugget was evaluated based on EBSD analysis.
• Microstructure evolution can be described as a dislocation manipulation process.
• Ultrasonic superposition influences recrystallization of weld nugget.
• Ultrasonic induced subgrain formation occurs in weld nugget center axis in UVeFSW.
• Superposition of static load on residual softening is sufficient for subgrain formation.

Recrystallization fractions in the stirred zone of Al 6061-T6 friction stir welds, prepared with and without ultrasonic vibrations, were evaluated using recrystallization fraction maps. Based on the maps, it was suggested that the microstructure evolution can be described as different dislocation manipulation processes. It was observed that superposition of static load of FSW on residual ultrasonic softening induces subgrain formation. Subgrain formation was substantial at the center of the stirred zone where the ultrasonic impact was the maximum.

Figure optionsDownload as PowerPoint slide