Friction-stir welding of AA6061-T6: The effects of Al2O3 nano-particles addition

Abstract

In the present work, attempts were made to fabricate Al-based nanocomposites by Friction Stir Welding (FSW) process. Al2O3 nanoparticles were added into the aluminum matrix for refining the microstructure of the nugget zone (NZ) and to restrict the growth of granularly in the heat-affected zone (HAZ). The effects of Al2O3 nanoparticles addition on the grains structure evolution and various mechanical behavior of friction stir welded aluminum matrix was studied and elaborated in detail. The findings revealed that the addition of Al2O3 nanoparticles resulted in remarkable refining of grains in the nugget zone due to pinning effect produced by nano-sized Al2O3 particles which prevent the grain growth followed by recrystallization during FSW, leading to a remarkable reduction in grain size. A significant increment in tensile strength, micro-hardness and wear properties compared to sample without nanoparticles under the same operating conditions is attributed to nano-sized Al2O3 particles addition in the nugget zone. Also, the samples joined with rotating and transverse velocities of 2000 rpm and 70/80 mm/min showed higher tensile properties. However, the employment of single FSW pass resulted in an unusual Al2O3 nanoparticles distribution and void initiation at the interface between Al-matrix and Al2O3 nanoparticles in the heat-affected zone resulted in the sudden premature fracture of the specimen during tensile loading.