Steel, cast iron, aluminum, magnesium, copper, zinc, glass, and polymers are the most commonly used materials.  

The European manufacturers have favored aluminum alloy 6016 for external panels, while 6111 is more common is the US.  Inner panels and sheet for unexposed applications are 5051, 5182, and 6181 in Europe, and 6111, 2008, and 5182 in the US.

You can obtain more information on usage and grades by using the following links:

http://www.steel.org/autosteel/technical_info/index.htm

http://www.cs.virginia.edu/icaa7/trends.pdf

http://www.advancedmanufacturing.com/July01/automotive.htm

Thank you for your reply.

In addition to the aluminium grades used, I don't suppose you happen to know the grade of magnesium used by Daimler Crysler in their Maybach engines do you?

A long shot perhaps.......

JD.

AZ91D has been the magnesium alloy used almost exclusively for valve cover applications.  It is the most common alloy, with the best die castability and highest strength, although it is limited in high temperature applications (creep, bolt load retention, etc.).  You can obtain more information on this alloy, magnesium die casting applications, and a newly developed alloy called AJ52x using the following links:

http://www.hydromagnesium.com/HITS/OSL02201.NSF/Files/PDF%20brochures/$file/Property%20datasheet.pdf

http://www.hydromagnesium.com/HITS/OSL02201.NSF/Files/brochures_pdf03/$file/Mg_Die_Casting_sec.pdf

http://www.magnesium-industry.com/Library/Highlights/Paper%20of%20the%20Month/papers/Temp%20Behaviour%20AJ52x,%20Heat%20resistant%20magnesium%20alloy%20for%20powertrain%20application.pdf