Simulation Of Temperature Field And Research On Weldability During Friction Stir Welding Of6061Aluminum Alloy

Aluminum alloy is a kind of material with such advantages as low density, highplasticity and easy processing. Meanwhile, Al is stored abundantly on Earth. Hence,aluminum alloy ranks the second behind steel as the most widely usedmaterial. However, using the conventional welding methods to weld aluminum alloysmay lead pores, cracks and other welding defects. A new welding method, which iscalled Friction Stir Welding (FSW), was proposed by TWI in1991. The abovewelding defects can be avoided or eliminated effectively by using FSW of aluminumalloys. The friction stir welding of aluminum alloy was studied both experimentallyand theoretically to optimize the welding parameters and broaden the use of FSW.Friction stir welding heat source model was established firstly. The temperaturefield of FSW was simulated by use of COMSOL software. The effects of suchparameters as the tool dimension, plunge force, rotational speed and welding speed ontemperature field were studied. Then, the tool size was selected and the scope ofwelding parameters was shrunk. The simulation results were used to guide thefollowing experiments.During friction stir welding of aluminum alloy6061-T6, self-designed tool andworkbench were used according to the above simulation results and achievements ofother researchers in the field.The effects of welding parameters on the welding jointwere studied. The results show when the rotational speed was600r/min, the weldingspeed was60mm/min and the plunging depth was0.1mm, the tensile strength ofwelding joint was the best. The tensile strength of the weld was226MPa, whichreached72.96%of tensile strength of the base material. The hardness of nugget zone,thermal mechanical affected zone and heat affected zone were measured. The resultsshowed the hardness of nugget zone was the highest and that of thermal mechanicalaffected zone was the lowest. The microstructure was observed by metallurgical testto explain the differences of different welding zones and the welding mechanism ofFSW was studied. The temperatures of four points located at different positions weremeasured. The computed temperatures were in good agreement with thecorresponding measured values, which verified the correctness of the simulation.