IN FOCUS: Lightweight aluminium weighs in to support A350 effort

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Airbus's bid to ensure its in-development A350 reaches full-rate production without the supply chain hiccups that have dogged arch-rival Boeing's 787 programme got a boost on 25 March with the formal opening of an industrial-scale foundry specially designed to produce the custom-mixed high-performance aluminium-lithium alloys that underpin the aircraft's structure.

Constellium, the Paris-headquartered aluminium group, cut the ribbon at its Issoire "Airware" foundry with one furnace capable of turning out 14t of alloy in two, 4m slabs twice daily. With a second furnace due for installation in June, the plant will by about year-end be able to turn out up to 48t of alloy daily. For each A350, Airbus and is suppliers will buy 80t of the Airware material.

An undisclosed amount is also to be supplied to Bombardier which is using it on the CSeries, and to SpaceX, for its Falcon rockets.

Only about 16t of that total actually flies; the rest is machined away in production to make the aircraft's wing ribs, seat rails and other components.

Material for the flight-test aircraft being assembled by Airbus was supplied from a small foundry at Constellium's research centre in Voreppe, France, where the Airware production process was developed. As Airbus senior vice-president for supply chain and procurement Eric Zanin told local politicians and Constellium suppliers and customers gathered at Issoire: "As of today Issoire is our number one aluminium-lithium supplier."

By a combination of metallurgy and the highly secret production process employed at Issoire, Airware promises to reduce the weight of metallic components and structures by up to a quarter compared while extending maintenance intervals to up to 12 years. And, says Constellium's aerospace and transportation business president Christophe Villemin, Airware can, unlike composites, be fed through the existing metallic-components supply chain and assembly lines, making it advantageous for ramp-up to large-scale production.

Constellium, claims Villemin, has mastered a technical problem that has otherwise daunted the aluminium industry - recycling of highly alloyed material. By being able safely and cost-effectively to extract lithium, and also silver and copper, from waste material, Constellium can reclaim those metals and produce new batches of Airware. Critically, he adds, this process means the alloy can economically, at the foundry, be custom-tailored to requirements.

And, he stresses, the material has moved beyond the laboratory to be available today on a mass production scale.

Constellium is not revealing customer names other than Airbus, Bombardier and SpaceX. Villemin says, however, that one of the key thrusts in development now is in wing skins, and the next big customers are likely to be for all-new programmes.

However, he adds that existing programmes can easily introduce Airware to save weight. A straight substitution of Airware for a traditional aluminium would cut weight by about 5%, but more savings can be had by redesigning components to exploit Airware's superior mechanical properties and corrosion resistance.

Whereas a decade ago metallurgists sought to add as much lithium as possible to aluminium alloys to reduce mass, Villemin says Constellium realised there was potential to produce a better overall end result by minimising the use of this very reactive metal. The result, he says, was a "surprising" improvement in corrosion resistance, as well as outstanding durability, from a project born about four years ago of the realisation that as an aluminium supplier Constellium - the former Alcan - had to make a leap forward to compete with rising demand for composites.

Airware's non-reactivity also means it performs extremely well alongside composites in the "hybrid materials environment" which Villemin sees as, increasingly, dominating aerospace design.