Property characterization of 2024Al/7075Al bi-alloy friction stir welded joints

Direct joining of damage tolerant 2XXX alloys with high strength 7XXX alloys offers the promise of fabricating tailor-made structural components. Butt joints in 1" thick plates of 7075-T7351 and 2024-T351 were produced by friction stir joining. Joints were sound and free of voids and root surface disbands. The joints have a joint efficiency (Fty) that is 80% of the parent metal 2024-T351. Properties are consistent as functions of depth and position along the length of the weld. Tensile failures are always ductile; elongations are typically 5%, which is a consequence of the deformation being localized to the lower strength heat-affected zones. The fatigue response (Kt=1.5 and R=0.05) of these weldments was determined in the weld nugget; both heat affected zones, and parent material. The lifetimes were shortest in the heat-affected zones, but were at least 1/3 of the parent metal lifetimes.