Effect of tool rotation speed on microstructure and tensile properties of FSW joints of 2024-T351 and 7075-T651 reinforced with SiC nano particle: The role of FSW single pass

Investigation on Friction Stir Weldability Characteristics of AA7075‐T651 and AA6061‐T6 Based Nanocomposites

“…e constituents of the two base metals are fragmented, and the fusion line is observed between the base metal at the left and the nugget zone at the right. Dispersion of h-BN agglomerates is noticeable along the fusion line at 500X magnification [19].…”

Nanoparticles reinforced joints produced using friction stir welding: a review

“…Also, Dragatogiannis et al [110] have observed that with the increase in both tool rotational speed (750-1500 rpm) and FSW passes up to three in the same direction during FSW of dissimilar AA5083-H111/ AA6082-T6/TiC it results in better distribution and mechanical mixing of TiC nanoparticles in the Al-matrix, while 750 rpm of tool rotational speed leads to poor mixing, especially in the flow arm that results in TiC nanoparticles agglomeration with clusters formation in the bottom of the NZ during the downward flow of the material induced by the tool shoulder. Bahrami et al [140] believed that higher tool rotational speed leads to more uniform SiC nanoparticles distribution in the NZ while lower rotational speed leads to the agglomeration of SiC (higher tool rotational speed) had a significant effect on the distributions of RPs in the NZ as shown in figure 25.Whereas, Kumar et al [52] observed SiC nanoparticles agglomeration in the top of the NZ at 450 rpm due to the less material flow from AS to RS at lower tool rotational speed during dissimilar FSW of AA2024-T351/AA7075-T651/SiC, while better material flow with homogenous SiC nanoparticles distribution along the grain boundaries in the NZ was observed at 1012 rpm due to higher heat input produced at higher tool rotational speed. They also stated that further increment in tool rotational speed from 1100-1800rpm results in stretching of SiC nanoparticles at 1270 rpm near the top surface of NZ along with RS which is attributed to the higher frictional force induced by the tool shoulder, as a result, material stuck to the tool shoulder and rotate about it that leads to defect in the NZ as shown in figure 26.…”

“…But due to the stirring action of the rotating FSW tool, it leads to the breaking of clustered RPs in the NZ and results in distribution homogenously. Many authors reported that the uniform distribution of RPs in the NZ during FSW is merely dependent upon the processing parameters (Kumar et al [52], tool pin geometry (Karakizis et al [119], number of FSW passes, and the pre and post-weld heat treatments (Moradi et al [111]) (figure 20) and tables 1 and 2 illustrate the effect of reinforcement particle and process parameters on various responses.…”

“…The intense stirring action induced by the rotating FSW tool and the SPD that occurred during the process leads to the change in the shape and size of the RPs in the microstructure of the reinforced FSW butt joints. Mirjavadi et al [47] observed that smaller-size reinforcement particles especially nanoparticles in the NZ had more pinning effect than the large-sized particles which helps in the refinement of microstructure during FSW of AA5083/TiO 2 , while Kumar et al [52] during FSW of AA7075/B 4 C observed that the presence of nano-sized B 4 C particles impedes the migration of dislocation in the base matrix that results in the reduction in the size of the B 4 C nanoparticles in the NZ due to the tool force and the stir action induced during the FSW process. While Chen et al [156] do not find any significant difference in the size/shape of the B4C nanoparticles in the NZ with no fragmentation and rounding off the B4C particles via the stir action of the FSW tool during the FSW of AA6063/B 4 C.…”

“…Kumar et al [52] observed the decrease in NZ microhardness in as-welded conditions during FSW of AA7075/B 4 C which is due to the softening that occurred in the NZ, as a result, the dissolution and dispersion of strengthening precipitates would occur, while Chen et al [156] observed that during FSW of AA6063/B 4 C the microhardness in the NZ was improved during artificial aging or PWHT-T6 similar to that BM due to the addition of the B4C particles those are agglomerated at the grain boundaries and the formation of new precipitates from the elements those are dissolved during the process that leads to the uniform precipitates distribution in the NZ and increase in microhardness, whereas the significant drop in the NZ microhardness was observed during PWHT-RRA due to the dissolution of GP zones during retrogression and growth and segregation of η' during reaging.…”