Abstract: This paper investigates the effect of different cooling conditions and varied tool rotations upon the weld quality of aluminium samples carried out by friction stir welding (FSW) process. In this work, aluminum alloy A356 samples were friction stir welded under air cooling, water cooling, lubrication oil cooling and nitrogen gas cooling at two different tool rotation speeds of 900 rpm and 1100 rpm. The study carried out is through experimental investigations. The effect of these processing parameters on mechanical properties and micro structural properties of welded joint are studied. Cooling the samples by liquid nitrogen or by lubrication oil was found to decrease the heat input during processing which limits the grain growth during the process. The decrease in heat input resulted in reducing the microscopic voids in the material leading to an increase in micro hardness and improvement of tensile properties. It was found that good machining properties can be achieved at the relatively higher rotational speed when no cooling condition is applied i.e. FSW is done in air. However, the best results out of all the samples were produced by liquid nitrogen cooling under tool rotational speed of 1100 rpm as it showed higher tensile.
Keywords: Friction stir welding, microstructure, cooling conditions, rotational speeds.