Advances in aluminium alloy products for structural applications in transportation

Abstract
This paper describes the needs of the aviation and automotive markets for structural materials and presents examples of developments of aluminum alloy products to fill these needs. Designers of aircraft desire materials which will allow them to design lightweight, cost-effective structures which have the performance characteristics of durability and damage tolerance. Their needs are being met by new and emerging materials varying from Al-Li alloys for thick structure, high-strength plate and extrusions for wings, and new monolithic and aluminum-fiber laminates for fuselages. Increase in fuel economy because of lighter weight structure is the driving force for aluminum alloys in the automotive market, and cost is extremely important. Mechanical properties for automotive use also depend on the application, and corrosion resistance must be adequate. For "hang-on" components such as fenders and hoods, formability is typically the limiting mechanical property. Strength must be adequate to resist denting at a thickness which offers cost-effective weight savings over steel. Because formability often decreases with increasing yield strength, alloys which are highly formable in the T4 temper and which age harden during the paint bake operation were developed. Alloys such as 6009 and 6010 are now being challenged by 2008, 6111 and 6016. Body structure components must be made from materials which absorb energy and fail gracefully during a crash. Such components for an automotive space frame are being die cast from an Al-Si-Mg alloy. These ductile die castings are joined to thin 6XXX extrusions which must combine formability, strength, ductility and the ability to deform plastically on impact. Bumpers must combine strength and adequate formability; in the event that current alloys are inadequate for future needs, a new 7XXX alloy offers an improved combination of properties.