Effects of heat input in friction stir welding on microstructure and mechanical properties of AA3003-H18 plates

The non-heat-treatable AA3003-H18 plates were joined by friction stir welding (FSW) to achieve a proper joint by optimizing the welding parameters. For this purpose, the effects of heat input on microstructure and mechanical properties of the welded samples were investigated by changing the ratios of rotational speed (800-1200 r/min) to travel speed (40-100 mm/min) (omega/nu). It was revealed that the grain growth rate was strongly increased with the increase of the heat input by rotational speed at constant travel speed, while the grain growth rate was slightly increased with the increase of the heat input by travel speed at constant rotational speed. Subsequently, hardness reduction was observed in the stir zone at higher rotational speed compared with that at lower one. An interesting observation was that various welding parameters do not have noticeable effect on the tensile strength of the FSW joints. Also, it has been observed that the fracture location of tensile test specimens was placed in the heat-affected zone (HAZ) on the advancing side at lower travel speed, while at higher travel speed, it was placed at the HAZ/thermomechanical affected zone (TMAZ) interface on the retreating side.