A Comparison Study of Mechanical Properties between Friction StirWelding and TIG Welded Joints of Aluminum Alloy (Al 6061-T6)


In this study two different welding processes have been considered, aconventional tungsten inert gas (TIG) and a relatively new solid state weldingknown as friction stir welding (FSW). TIG welding process has been performed onAl 6061-T6 of thickness 4mm by using filler metal of Al-Mg alloy type (ER5356)according to AWS classification metal with tungsten electrode (EWth-2) and arcvoltage of (12V). Various welding currents of (125, 160, 200, 225) Amp were usedunder argon as shielding gas of flow rate of (15-20 cf / hour) and welding speed of280 mm/min.Friction stir welding is carried out using automatic milling machine with fivedifferent welding or bed speeds of (25-50-80-100-125 mm/min) and five differenttool rotation speeds of (630-800-1000-1250-1600 rpm). Tool steel of type R18consists of a shoulder with diameter of (20 mm) and pin of diameter (5.5 mm). Xrayradiographic inspection, tensile test and microhardness test of FSW and TIGjoints at optimum welding conditions were made.The results indicate that the best tensile strength of FSW joints is 289 MPa andjoint efficiency is 79% which were welded with welding parameters of (1250 rpm,800 rpm and 50 mm/min, 125 mm/min) respectively. While in case of TIG joint thebest tensile strength is 210 MPa and joint efficiency is 57%.It was found that the microhardness hardness values in the TIG welded jointsare lower than that of the FSW joints. The formation of fine equiaxed grains andvery fine strengthening precipitates (Mg₂Si) in the stir or weld region are thereasons for higher tensile strength and hardness of FSW joints compared to TIGjoints.