Metal Information Center

Airbus plans to use alloys of aluminum and lithium

December 22, 2007 – 6:59 am

From the 10th plane on, each of the new A320 series of short-range 150-seaters rolling out of Airbus Industrie’s final assembly facilities at Toulouse, France, could contain several hundred pounds of aluminum-lithium alloys. That also will be the case for other commercial aircraft programs planned by this European consortium.

“I’m absolutely convinced that all the planes built after 1987 will have some aluminum-lithium components,” said Douglas H. Jagger, the consortium’s general manager of technical development for future programs. “And even though they certainly have some reasons for what they say, I think Boeing Co. are shooting the light in stating that they will represent 100 percent of the aircraft by 1990.”

Also, Dr. Colin Baker, the chief expert on aluminum-lithium alloys at British Alcan Aluminium Ltd., thought it “very unlikely” that 90-percent composite or all-composite planes would be hitting the runways before the year 2000.

Baker declined to offer alternative forecasts, but he mentioned a recent statement by British Aerospace Plc, a member of the consortium, which gave composites shares of only 10 and 35 percent, respectively, of the total structural weight of new commercial and military aircraft by 1995.

Jagger stood by a year-old forecast (AMM, Feb. 21) that composites could take up 20 percent of the structural weight of new aircraft by 1990, but that figure may well be revised downward if aluminum-lithium alloys prove as effective as British Alcan and other aluminum producers claim.

Nobody is really certain in Europe as to which material would win the battle between composites and aluminum-lithium alloys as replacements for the heavier conventional families of zinc and copper-based aluminum alloys. But while companies’ public statements are far more cautious and reserved than those of their United States competitors, European officials seem to be taking a lot more interest in aluminum-lithium than a year or so ago, and this is being reflected in the marketplace.

A few months ago, for example, new expectations of overcapacity in the market led Pechiney and Hercules Inc. to suspend indefinitely the establishment of a projected French joint venture in composites. Meanwhile, a Pechiney subsidiary, Ceoedur, is gearing up to supply its first test samples of aluminum-lithium alloys to the aircraft industry in the second half of this year, after British Alcan and Aluminum Co. of America.

Baker said British Alcan is getting ready to supply annually between 2,000 and 4,000 metric tons of aluminum-lithium alloys, evenly divided between the commercial and the military aircraft industry, out of a new pilot plant that will start producing larger castings and slabs in the spring of 1985.

British Alcan, which inherited the aluminum-alloys business from the former High Duty Alloys on the basis of a 13-year-old research contract from the British Ministry of Defense, is beginning to ship 1-ton ingots for sheet and plate and 12-inch extrusions, and it will probably add later this year 16-inch extrusions as well as forgings, rod and wire and the first shape castings in the new material.

However, it has not quite yet reached its goal of making the alloys 10 percent less dense and 10 percent stiffer than conventional aluminum alloys, Dr. Baker admitted, adding that further research work will be required to give the material acceptable damage-tolerance and corrosion-resistance properties.

Because of obligations to the military, the first priority for British Alcan has been to develop a suitable general purpose aluminum-lithium alloy to replace the 2014 family of copper-based aluminum alloys for non-critical applications, and samples of this new type of alloy were delivered to the members of the Airbus consortium between March and October of last year.

Baker said the emphasis at British Alcan is shifting to the development of a suitable high-strength substitute for the 7075 series of zinc-based aluminum alloys, but according to Jagger, its application to upper wing skins and fuselage frames will only occur in about 10 years’ time.

Meanwhile, British Alcan is defining together with British Aerospace, one of the members of the Airbus consortium, the specifications for a new type of fatigue and damage-tolerant aluminum-lithium alloy that should replace the 20243 series of copper-based aluminum alloys, typically in wings’ lower skins, in fuselage skins and possibly in rib spars. Neither Jagger nor Baker could predict when the substitution will start to happen.

Baker claimed that British Alcan’s new alloys possess “satisfactory” degrees of corrosion resistance to salt and to atmospheric conditions, but said his firm may have to develop “a whole new generation of alloys” to achieve sufficient resistance to stress corrosion.

British Alcan has been supplying experimental samples of aluminum-lithium alloys to Boeing since 1981. Boeing “is pushing faster” than the other civil aircraft manufacturers for their adoption, according to Baker. Jagger admitted that members of Airbus’ materials committee are only currently in the process of agreeing on the specifications required for designing aluminum-lithium parts.