SWEPT FSSW IN ALUMINUM ALLOYS THROUGH SEALANTS AND SURFACE TREATMENTS

An investigation of the effects that faying surface treatments have on the mechanical properties and the corrosion resistance of friction stir spot welded joints between AA7075-T73 to AA2024-T3 sheet materials has been conducted. The test panels consisted of 0.040 '' thick bare AA2024-T3 panels with 0.040 '' thick AA7075-T73 flat stiffeners. The dissimilar alloy sheets were treated with Alodine 600, and a sealant was placed on the faying surface of the welded components. The sealants chosen for this experiment were PRC-DeSoto PR-1432 GP and PRC-DeSoto PS 870 GRV. Coupons without sealants were also evaluated to establish a baseline for a statistical comparison. Four weld tools were used for these experiments, each having a different flow direction relative to the shoulder: 1) neutral, 2) additive, 3) subtractive, and 4) mixed. Mechanical properties of selected coupons were evaluated using a guided 4-spot configuration and were tested to the ultimate lap shear strength and in fatigue. Corrosion tested coupons were welded with a single spot configuration.