A high-strength steel is being developed at Missouri University of Science and Technology (R&T) that could help auto manufacturers in their quest to meet future fuel efficiency requirements.

“We are currently refining the steel design to achieve ‘Gen 3′ mechanical property goals while also maintaining manufacturability,” says center director Ronald J. O’Malley.

Under the U.S. Department of Transportation’s Corporate Average Fuel Economy (CAFE) regulations, auto manufacturers must improve the fuel efficiency of their vehicles each year through 2020. Regulators have set a tentative goal of increasing fuel efficiency to 54.5 miles per gallon for cars and light trucks by the 2025 model year.

So-called first-generation steel is most commonly used in today’s cars and trucks. A second-generation product has been developed, and it is stronger Physical characteristic of martensite in a steel sample. Source: Wikipediaand more lightweight than the first-generation material. However, O’Malley says it is too costly to produce and more difficult to manufacture. The third-generation steel could be lighter, easier to make and strong enough to address automakers’ safety concerns.

The S&T researchers are using a method known as TRIP—or transformation-induced plasticity—to obtain the performance required to meet both safety and CAFE goals. It involves transforming an unstable crystal structure known as austenite, which normally exists at high temperatures, into martensite, a harder substance that develops as the steel deforms.

“The S&T alloy design employs a two-stage or ‘dual TRIP’ mechanism that leads to extreme work hardening and energy absorption, so it’s very good for automotive crash-worthiness,” says O’Malley.

The Missouri S&T team has used an atomic modeling method known as density functional theory to identify alloying elements to create the dual TRIP character of these new steels.

The challenge, however, lies with the large-scale production of these new steels. With the help of industrial partners, the researchers are examining all aspects of the steel manufacturing, from melt practice to final formability by the automotive producer, O’Malley says. A committee of representatives from four steel manufacturers—Nucor, U.S. Steel, AK Steel and ArcelorMittal—oversees the project.

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