The use of aluminum in automobiles is by no means ground-breaking news. Sixteen years ago Honda pioneered the first all-aluminum unibodied mass-produced vehicle with the NSX. Since then we've seen automakers turn to aluminum to reduce the weight of drivetrain components, body parts, suspension parts and the chassis while Audi has quite possibly been aluminum's loudest proponent among the major manufacturers.
If you'd like to delve a little deeper into the use of aluminum in cars, here's a short, fun New York Times article discussing the matter. The first issue they tackle is the fact that while aluminum is about one-third the weight of steel, it's also about one-third as stiff. You might extrapolate that this being true, the amount of aluminum used in a vehicle would have to be about three times that of steel, so no weight savings would be realized, but you'd be wrong. The key is that the thickness of any given material used is determined not directly by material strength, but by its resistance to buckling when formed into specific shapes. Because of aluminum's specific properties, it can often be reduced to about 1.5 times the thickness of a corresponding steel structure at only about half the weight. For instance, the Audi A8 aluminum space frame tilts the scales at just 548 lbs which is 46 percent lighter than it would have been if manufactured from steel.
The article also mentions that recent developments in aluminum casting techniques can produce parts that are nearly as strong as if they were forged. Unfortunately, the depth of the article prohibits the author from getting into deeper levels of detail, however, it remains an interesting, light read if you've got the time.
[Source: New York Times]