Aluminum alloys with eco-friendly materials and excellent recovery rat ar widely used in the various industries as structural panels consisting of a double structure with outer panels and inner panels. The outer panels are especially required to allow high strength and denting resistance. Inner panels must have good formability and drawability.
Recently, Friction Stir welding (FSW) drew attention because it has lower distortion and defect formation. Many reserchers have investigated for friction stir welding of aluminum alloys.
The focus of this investigation is to evaluate the effect of plunge dpeth and joining parameter on welding shape and mechanical property''s relationship. The dissimilar Al alloys, KS5J32 and AA6K31, were joined by friction stir lap welding technique each welding speed and plunge depth. KS5J32 alloy was placed on the top of AA6K31 alloy. The tool rotation speeds were 1000, 1250 and 1500rpm, and the welding speed were 100, 300, 500, 700mm/min, respectively. Other parameter is plunge depth changed 0, 0.2, 0.45mm respectively. The welding tool was rotated in the clockwise direction and tool angle is 3°.
The result showed that three shapes of nugget, such as onion ring, irregular vortex type and interface type, were observed with various revolutionary pitch and plunge depth. Void defect was observed lower heat input condition at 0.45mm plunge depth. Fractured positions were classified into two types: interface fracture and AA6K31 fracture depending on the revolutionary pitch and plunge depth. Interface fraction was occurred 0mm plunge depth and the strength was 67% of base metal. AA6K31 fracture position classified into four types: B.M, HAZ, TMAZ and Void fracture. B.M fracture''s has the highest strength at 0.2mm plunge depth another fracture types. The relationships were weld shape and fracture starting location due to plunge depth and revolutionary pitch. Plunge depth was decreased with increasing peak load except interface fracture conditions. Lower than 0.15 revolutionary pitch values have same peak load and fractured thickness. The important factor of friction stir lap welding was lower plunge depth as prevented defect formation and interface fracture. Also void defect does not have condtion is a proper welding condition.