Characterization of Microstructural Refinement and Hardness Profile Resulting from Friction Stir Processing of 6061-T6 Aluminum Alloy Extrusions

Abstract

In this study, the change in microstructure and microhardness adjacent to the tool during the friction stir processing (FSP) of 6061-T6 extrusions was investigated. Results showed that the as-received extrusions contained Fe-rich constituent particles with two distinct size distributions: coarse particles in bands and finer particles in the matrix. After FSP, Fe-containing particles exhibited single-size distribution and the coarse particles appeared to be completely eliminated through refinement. Microhardness tests showed the presence of four distinct zones and that hardness increased progressively from the dynamically recrystallized closest to the tool, outward through two distinct zones to the base material. The similarities and differences between the results of this study and others in the literature are discussed in detail.

Effect of Forced Air Cooling on the Microstructures, Tensile Strength, and Hardness Distribution of Dissimilar Friction Stir Welded AA5A06-AA6061 Joints

“…Near the NZ and TMAZ, the hardness was partially improved due to the refinement of the grains as a result of the stirring action. For the AA6061 side, a dramatic drop in hardness was observed in the HAZ due to the coarsening of the grains and the dissolution of the precipitates [35]. The HAZ of AA 6061 became the weakest area in the FSW joint.…”

Characterization of Tool Degradation during Friction Stir Processing of 6061-T6 Aluminum Alloy Extrusions

“…A micrometer was used to measure the pin tool diameter, placed in contact with the tool shoulder after cutting each section, in the same spot in every measurement procedure. Additional details about the experiments and resultant microstructures in the aluminum alloys are provided elsewhere [16,17].…”