Metallurgy and materials science are, at the risk of being redundant, sciences. There's no magic metal, no magic material. The best a designer can do to design for performance is to select the best material for the application, and "best" is subject to real discussion. But the designers don't have the last say these days. The EPA, the marketeers, and other non-design, non-engineer exterior influences drive materials decisions away from the optimum. So you get plastic gears where aluminum would be more durable, composite oil pans that leak, aluminum truck beds, etc. Good for the consumer? No. Good for the company? No. Compliant with government mandates established by people who couldn't design a gum wrapper? Yeah, you betcha.
