Fabrication of AA6061-T6/Al<sub>2</sub>O<sub>3</sub> Reinforced Nanocomposite Using Friction Stir Welding

Abstract

In the present work, attempts were made to join AA6061-T6 sheets by Friction Stir Welding (FSW) process. Al 2 O 3 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). In order to illustrate the influence of Al 2 O 3 nanoparticles on mechanical properties, namely ultimate tensile strength, micro-hardness distribution, and wear resistance of the welded joints, FSW was conducted with and without nanoparticles at a constant rotating velocity of 2000 rpm and transverse velocity of 70 mm/min. For characterization of microstructures, optical and scanning electron microscopes were employed. The findings revealed that Al 2 O 3 nanoparticles addition along the joint line resulted in remarkable refining of grains structure in the weld nugget zone. This was due to the pinning effect produced by nano-sized Al 2 O 3 particles which prevent the grain growth followed by recrystallization during FSW, leading to a remarkable reduction in grain size. Also, the sample with nanoparticles joined at rotating and transverse velocities of 2000 rpm and 70 mm/min showed higher tensile properties than the sample without nanoparticles. However, the employment of single FSW pass resulted in an unusual Al 2 O 3 nanoparticles distribution and void initiation at the interface between Al-matrix and Al 2 O 3 nanoparticles in the heat-affected zone resulted in the early fracture of welded joints during tensile loading. Moreover, Al 2 O 3 nanoparticles addition results in the reduction of frictional coefficient and increment in wear resistance due to fine small grains size and large distribution of hardness in NZ of friction stir welded specimens.