Structural parts
With a few exceptions, structural parts are constructed of steel. With the problems of joining technology and electrical insulation (corrosion ratings) solved, aluminum and stainless parts are being used increasingly for their light weight and strength.
However, the weight advantages of total aluminum structures have been marginalized by new, high-strength steels. Therefore, the high cost of material and the extensive processing involved are only justified in luxury cars (such as the Audi AM and Jaguar XJ).
Hang-on parts and outer skin
Unlike structural parts, the design and weight of outer materials are important considerations. Easily-formable steels and aluminum (and plastics) are being used widely for outer skins of vehicles.
Both improved process reliability, via Schuler technology, plus the development of formable high-strength and easily-formed materials are expected to lead to stronger automotive outer skins.