Microstructure and mechanical properties of 6082-T6 aluminum alloy joint by high speed friction stir welding

6 mm thick 6082-T6 aluminum alloy plates were welded by friction stir welding at a high welding speed of 2 000 mm/min, and microstructure and mechanical properties of the joint were studied. Experimental results showed that sound FSW joints without defects in the nugget zone were achieved at a high welding speed. Discontinuous “S” line was observed in the nugget zone. Grains in the nugget zone were refined to 10 μm, and coarsening of the precipitates in the heat affected zone were significantly inhibited. The lowest hardness clearly increased to 72 HV, which reached to the similar level of the nugget zone(75 HV). In tensile test, joints fractured in the heat affected zone. Tensile strength of the joint was 262 MPa, up to 85% of the base metal, which was better than that of the joint under conventional parameters. This study showed that high welding speed friction stir welding of aluminum alloy could not only improve the mechanical properties of the joint, but also significantly improve the welding production efficiency.