Microstructure, Texture Evolution and Mechanical Characteristics of Ultrafine-Grained Structure in Friction Stir Processed Aluminum Alloys

In the present study, multiple consecutive passes of cooling-assisted overlapping friction stir processing (FSP) were carried out to produce a bulk ultrafine-grained (UFG) structure in aluminum alloys. This technique involved the use of cooling media during the FSP, which, combined with the intense plastic straining inherent to the process, significantly refined the material’s grain size to sub-micron dimensions, approximately 900 nm (i.e., UFG structure). The microtexture and mechanical characteristics of the processed sample were investigated. The results showed that specific texture components, particularly the Copper and A texture components, had a notable impact on the resulting texture of the processed alloy. The FSP resulted in the reduction of microhardness and tensile strength due to thermal softening and precipitate dissolution. Furthermore, the formation of the UFG structure enhances the elongation of the processed material. The elongation increased by approximately 120%, indicating a significant improvement in the alloy’s ductility due to the UFG structure achieved through the cooling-assisted overlapping FSP.