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October 14, 2010

brake rotors out of aluminum

high strength, high temperature aluminum will enable brake rotors to be built
from aluminum.
http://www.mtu.edu/news/stories/2010/october/story31850.html

Aluminum brake rotors will save about 50 pounds in all cars and reduce
fuel consumption
by 0.8%.

If you could make rotors out of aluminum, says Paul Sanders, the
average car would lose about 50 pounds. “That’s a big number on a
car,” says Sanders, an assistant professor of materials science and
engineering at Michigan Technological University. “Every 10 percent
saved in weight on a vehicle equals roughly 4 percent in fuel economy.
You could save 0.8 percent in fuel. It doesn’t sound like much, but it
can be huge for the fleet.”

Manufacturers haven’t made the switch because aluminum starts losing
strength at relatively low temperatures, 250 degrees Celsius (about
480 degrees Fahrenheit). “If you had aluminum brakes, driving down
Pike’s Peak would do you in,” Sanders says. “We wanted to design
aluminum alloys which maintain their strength up to 400 degrees.”A

To do that, Sanders and his team of graduate students and
undergraduates are using different elements in making the aluminum
alloy. Traditionally, silicon, copper and magnesium are added to
aluminum to improve its properties. Sanders is replacing them with
minute quantities of an exotic blend of zirconium and rare earths,
including scandium.

So far, his strategy is working: the hardness of the new alloy peaks
at the magic 400 degrees. Now, the team is preparing to run tensile
tests on the metal in cooperation with students from Northwestern
University, where Sanders earned his PhD. “We suspect that it will be
good in both areas—strong and stretchy,” said Sanders. “Typically,
materials are good in one but not the other.”

A high-strength, high-temp aluminum might also replace iron and steel
parts in turbochargers, which can get up to 500 degrees and hotter.
And it could supplant the standard aluminum alloy used in most
pistons. As engines get more efficient, they generate so much heat
that pistons made with conventional aluminum have to be sprayed with
oil to prevent overheating and strength loss . “We could replace that
entire mechanism, and we would like to collaborate with Tech’s
mechanical engineering department to incorporate these new alloys in
new engine designs ,” Sanders said.

The team is also experimenting with a variety of rare earths to
replace the scandium, which has one disadvantage: it costs about
$3,500 a kilogram.



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