Ford used heat-treated aluminum alloys in the F-150 cab, hood, tailgate, floor, fenders, doors, front end, pickup box, and numerous other parts. About 95% of the new body is made from aluminum alloys, offering a yield strength of about 45 ksi, while the frame is composed of high-strength steel. Together, the aluminum alloys and the high-strength steel eliminate about 700 pounds from the overall vehicle weight. An F-150 4 x 4 crew cab, for example, drops from about 5,500 pounds to about 4,800.
Similarly, General Motors knocked 99 pounds out of the Chevy Corvette frame by switching to aluminum. To do that, GM invested $52 million in a body shop that manufactures the frame, using a technique that allows aluminum to be spot welded to aluminum. Chevy also employs laser welding and laser vision inspection to complete the structure, which it says is 57% stiffer than predecessors.
The use of such materials can be costly. Some automotive engineers estimate that the materials make up as much as $1,000 of the cost of some new trucks, especially those using large quantities of aluminum. That's why GM has chosen advanced steels over aluminum in many applications, such as the new Chevy Silverado pickup and the Cadillac ELR plug-in car.
"A lot of the people who buy trucks are ordinary Joes," Wilkinson said. "They're not luxury car buyers. So you have to be careful not to price the trucks right out of the price range of those folks."
For design engineers, the cost and performance tradeoffs loom large right now, especially because so many automotive programs are launched four, five, and even six years ahead of their introduction dates. Engineers say they need time to develop steel and aluminum alloys jointly with suppliers. Then they have to learn to manufacture the materials and design them into the vehicles. Moreover, those challenges need to be balanced against the rapid improvements made by material suppliers. "It's been said that 50% of the steels in today's cars didn't even exist 10 years ago," DePompolo said. "That shows you how fast this is all changing."