Alcoa Inc.

Dhurba J Chakrabarti

Jen C Lin

John Newman

Gary H Bray

Diana K Denzer

Cagatay Yanar

Greg Venema

Aluminum alloy products about 4 inches thick or less that possesses the ability to achieve, when solution heat treated, quenched, and artificially aged, and in parts made from the products, an improved combination of strength, fracture toughness and corrosion resistance, the alloy consisting essentially of: about 6.8 to about 8.5 wt. % Zn, about 1.5 to about 2.00 wt. % Mg, about 1.75 to about 2.3 wt. % Cu; about 0.05 to about 0.3 wt. % Zr, less than about 0.1 wt. % Mn, less than about 0.05 wt. % Cr, the balance Al, incidental elements and impurities and a method for making same. The invention alloy is useful in making structural members for commercial airplanes including, but not limited to, upper wing skins and stringers, spar caps, spar webs and ribs of either built-up or integral construction. The invention alloy may be aged by 2 or 3 step practices while exceeding the SCC requirements for applications for which the invention alloy is primarily intended. The flexibility of the invention in this regard is useful for its application in multi-alloy or multi-material systems joined by welding or bonding and subsequently aged.

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Export, PA, United States of America

Dhurba J Chakrabarti