Investigation On Friction Stir Welding Process Of 7B04 High Strength Aluminum Alloy Lap Joints

The friction stir welding process of 7B04 high strength aluminum alloy lap joint for2 mm thickness plate was studied in this paper. The influence of surface oxidation film, needle length, welding process parameters on weld surface forming, interface shape and tensile properties was discussed. The welding process parameters were optimized.The results indicate that the oxidation film has a little effect on tensile properties of the aluminum alloy lap joints. The tensile force of welded joint increases firstly and then decreases with the needle length increasing when the welding process parameters are constant.The extension size of retreating side to advancing side increases and the upward migration size of the advancing side decreases with the welding speed increasing. The tensile force of welded joint increases firstly and then decreases with the welding speed changing between 50 to 300 mm/min when the rotating speed and the plunge depth of the shoulder are constant.The tensile force of welded joint increases firstly and then decreases with the rotating speed changing from 400 to 1000 r/min when the welding speed and the plunge depth of the shoulder are constant. The advancing side of the interface produces hole when the rotating speed is very low and the interface of advancing side has a little upward migration trend when the rotating speed is very high. The migration size of the retreating side decreases and the interface of the advancing side has no upward migration with the plunge depth of the shoulder increasing. The tensile force of welded joint increases gradually with the plunge depth of the shoulder changing from 0.1 to 0.4 mm when the rotating speed and the welding speed are constant. The tensile force of welded joint becomes the highest and the interface is better when the needle length is 2.8mm, the welding speed is 200 mm/min, the rotating speed is 600r/min and the plunge depth of the shoulder is 0.3 mm. The welding process parameters are optimized using the response surface method. The peak value of the tensile force of weldedjoint is 8649 N when the welding speed is 177mm/min, the rotating speed is 682r/min, the plunge depth of the shoulder is 0.3mm.