Mechanical properties of severely plastic deformed aluminum sheets joined by friction stir welding

The severely plastic deformed aluminum sheets were joined by friction stir welding (FSW). The technique used for imposing the severe strain to the sheets was constrained groove pressing (CGP) process. The specimens with three different imposed strains by CGP, which lead to different initial microstructures, were joined at various rotation (ω) and traveling (V) speeds. The microhardness measurements and microstructure investigations were carried out. It was revealed that after FSW process of the specimens strained by CGP process, grain growth and correspondingly hardness reduction were observed at the stir zone. Also, transverse tensile test was performed at all conditions. For the CGPed samples, it has been observed that with increasing the rotation speed, the strength of weld was decreased while the effect of traveling speed on the strength was different at various strains. Furthermore, the results achieved from FSW of severely deformed samples were compared with the results achieved from FSW of annealed ones.

► Severely deformed aluminum sheets are successfully joined by friction stir welding.
► For CGPed specimens, significant reduction in hardness of stir zone occurs.
► Microstructures of joints contain equiaxed and elongated grains.
► Increasing of rotation speed reduces the strengths of 1 and 2 passes CGPed samples.