Lighter cars and airplanes could be on the horizon thanks to an advance in the manufacture of steel. Researchers have found a way to strengthen the metal and reduce its density—and without increasing costs.
The advance might translate to an extra 1 mile per gallon (2 liters per kilometer) in gas mileage for a standard car, estimates materials scientist Alan Russell of Iowa State University in Ames, who was not involved with the work. That’s not enough to make drivers jump for joy at the gas pump, but “it’s really quite a substantial achievement,” he says.
Producing strong, lightweight materials is a delicate balancing act. Lighter materials tend to be weaker, and stronger materials tend to be more brittle. Glass, for example, is strong but brittle: You can try to bend or stretch it with your hands and it won’t budge, but drop it on the floor and it shatters.
One method of making steel lighter is to add aluminum, a less dense metal. In steel, aluminum forms an ultrastrong compound with iron. That strength is an asset, but the compound tends to arrange into brittle bands. To disperse the aluminum compound and make the metal less brittle, researchers led by materials scientist Hansoo Kim of Pohang University of Science and Technology in South Korea added nickel, which caused the aluminum compound to permeate the metal in nanometer-sized clusters instead of long bands. The clusters are too small to cause the undesirable brittleness, but the strength and lightness of the aluminum remain, the researchers report online today in Nature. The researchers examined their steel with an electron microscope to confirm that the aluminum clusters had formed. Then they tested the metal by applying tension and found that it was stronger and less brittle than conventional steel.
The new steel is an “interesting and novel development” that stands a good chance of eventually being adopted by industry, says metallurgist P. Chris Pistorius of Carnegie Mellon University in Pittsburgh, Pennsylvania. But it’s not a dramatic leap forward, he says. “This is a very significant increment, but it does build on what we know about how steels work.”
Where the new metal really shines is in its cost. Other lightweight, strong metals such as titanium alloys are too expensive to be used in passenger vehicles. The low price of the metals used to produce the new steel means that the price will be closer to that of standard steel, Russell says, so automakers could use it to lighten their loads without driving up costs. “That’s the kind of thing that makes engineers salivate freely,” Russell says. “They love that kind of improvement.”