Fatigue crack propagation behavior of friction stir welded 5083-H32 and 6061-T651 aluminum alloys

The fatigue crack propagation (FCP) behavior of FSWed 5083-H32 and 6061-T651 specimens were examined with the fatigue crack growing either parallel to the dynamically recrystallized zone (DXZ) at variable Delta K values and an R ratio of 0.1 and 0.8, respectively, or perpendicular or 45 degrees to the DXZ at various constant Delta K values and an R ratio of 0.1. Residual stress was measured on the top surface of FSWed plate either perpendicular or parallel to the welding direction and the residual stress-corrected Delta K, Delta K-corr, is calculated based on the K, the stress intensity factor at residual stress, for the DXZ specimens to quantify the compressive residual stress contribution to the FCP rates. The present study suggests that the FCP behavior of FSWed 5083-H32 and 6061-T651 specimens in the DXZ is mainly determined by the beneficial compressive residual stress reducing effective Delta K and the detrimental grain refinement causing intergranular fatigue failure. The FCP behavior of FSWed 5083-H32 and 6061-T651 specimens is discussed based on residual stress measurement and fractographic observation. (c) 2007 Elsevier B.V. All rights reserved.