Alcoa offers alloys to cut 787 weight

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Supplier also focuses on next-generation narrowbodies

Alcoa is offering Boeing new aluminium-lithium alloys to help with the 787's weight problem. Developed within the last 18 months to two years, the lightweight alloys could replace the conventional aluminium, and perhaps some of the titanium, the company believes.

Alcoa is already supplying its proprietary 7085 aluminium alloy for the largely composite 787, and aluminium-lithium could replace this in areas such as the wing spars and engine pylons, says Mark Wallis, president, North American rolled products. The new alloys are the first developed for plate, rather than sheet, products designed to be machined to produce lighter, simpler monolithic parts.

The company is also working to replace titanium with aluminium-lithium on the 787, because of concerns over the rising cost and tightening availability of the strategic metal, which is used more extensively in the 787 than in any previous Boeing. Of the 787's structure weight, 15% is titanium, 20% aluminium and 50% composite.

"The issue with titanium is the significant increase in price, and 787 demand will stress the supply," says Helmut Wiesel, Alcoa group president, global rolled products. "We are working on a number of alloys, some to replace titanium and also others to compete with composites."

Despite the largely composite airframe, the value of Alcoa's content on the 787 is close to that on the 767 because of extensive use of its fasteners and engine aerofoils. Even if a switch to aluminium-lithium does not increase Alcoa's share of the structure weight, it will boost its value, Wallis says, because of the significantly higher price of the new proprietary alloys.

Fighting back against perceptions that aluminium is losing ground to composites, Alcoa says it is already developing products for the next-generation single-aisle aircraft that it expects to replace the Airbus A320 and Boeing 737 beginning around 2013-15. Arguing the emphasis for these volume-produced aircraft will be on low cost, the company believes the composite technology developed for the widebody 787 and Airbus A350 XWB will not automatically read across to the new narrowbodies.

Wallis says Alcoa is working on hybrid metallic/composite materials that would compete with carbonfibre.


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