Friction stir welding of AA5052: the effects of SiC nano-particles addition

In the present work, the AA5052 aluminum sheets were joined by friction stir welding (FSW) technique. In order to refine the microstructure of stir zone (SZ) and to prevent the grain growth of heat-affected zone (HAZ), the SiC nano-particles were added to the weld nugget. To obtain the optimum condition for FSW, three rotational speeds (800, 1000, and 1250 rpm) and three traveling speeds (30, 50, and 80 mm/min) were applied. Microstructural evolutions were characterized using optical and scanning electron microscopes. Besides, the mechanical properties (tensile strength, hardness, and wear test) of weldment were also studied. The results showed that adding the SiC nano-particles led to the significant grain refining of the welds. However, the improper SiC powder distribution during one pass of FSW resulted in the premature fracture of workpiece. The specimens joined at the rotational speed of 1000 rpm and welding speeds of 50 and 80 mm/min exhibited the highest ultimate tensile strength.