When MIT's Technology Review magazine recently named their Top 100 Young Innovators for 2002, a GM Staff Research Scientist and Group Manager in the Materials and Processes Lab made the list. Paul Krajewski joins 99 other innovators under the age of 35 whose work in business and technology profoundly impacts today's world. In Krajewski's case, he is lightening the load for automobiles by developing new aluminum alloys and forming methods. To date he's earned six patents, with more pending.

"My work reflects a theme that's been ongoing since I joined GM - the need to improve formability of aluminum," says Krajewski. Using aluminum helps reduce overall vehicle weight, because the metal is 40 percent lighter than steel. Less weight translates into greater fuel efficiency for the GM fleet.

But manufacturing vehicles with complex aluminum parts poses many problems. "If you take a sheet of aluminum and place it in a die designed for steel, in many cases the sheet will split during stamping. The inherent plasticity or formability of aluminum is not as good as steel," Krajewski explains. "So I've been involved in two projects: one to develop heat treatments for aluminum, the other to develop methods for forming at elevated temperatures."

The Heat Is On
Retrogression heat treatments for aluminum involve applying temperature in a controlled manner to change the metallurgical structure and enhance forming. The idea for these heat treatments originally came from the aluminum ladder industry.

"To make an aluminum ladder, manufacturers drill holes in the side rails and then heat the ends of the rungs before inserting them into the holes," says Krajewski. "They then compress each one, so that all along the rails are holes with crumpled metal that fits around the rung ends. That wouldn't be possible without applying heat - the aluminum would break."

Krajewski's challenge from his supervisor, Ed Ryntz, was to apply this heat treatment technology to the auto industry. He spent several years in the laboratory, working to learn whether these retrogression heat treatments would work on alloys of interest to the auto industry, what effect they would have, and where they could best be applied. Finally, Krajewski learned how to tailor the heat treatments to automotive-specific alloys.

Armed with this knowledge, he worked with Ryntz to market the technology within GM, talking with groups that might benefit from trying a new technique. Eventually the former Truck Group and Metal Fabrication Division realized that heat treatments had the potential to solve several problems they were facing. One of these problems occurred during hemming, an operation that involves folding the flange of an outer vehicle panel over an inner panel. Hemming aluminum panels usually causes it to break at the edge of the bend.

"We focused on a heat treatment for the Suburban's aluminum liftgate, working with the groups from the early preproduction stages right up to production," says Krajewski. "To ensure that the panel wouldn't crack during hemming, we developed a small fixture that provided a heat treatment around the panel just before it was folded. Later, when the same problem arose during production, we designed another fixture that could be used in the assembly process."

The project gave Krajewski a chance to participate in research and development from start to finish: "We conducted the lab research, then developed a process that was used in production. Now, every time I see a Suburban on the road, I know that work I did impacted part of that vehicle." (See Figure 1.)

Figure 1. Paul Krajewski, named one of Technology Review's Top 100 Young Innovators for 2002, shows off a Suburban liftgate manufactured using a heat treatment process and fixture he developed.

An Unlikely Combination
Krajewski has also been involved in warm forming - conventional stamping of aluminum at elevated temperatures. For that, however, he may be best known for developing an improbable new lubricant using milk of magnesia.

"One of the challenges when you try to stamp or form things at elevated temperatures is that many lubricants don't hold up," says Krajewski. "Typical oils and greases burn away, because they can't tolerate the high temperatures." Lubricants designed for high temperatures typically come with a high cost as well.

Krajewski recalled that a friend in graduate school, Brian Worth, had used milk of magnesia as a release for elevated-temperature tensile testing. After running a series of experiments, Krajewski showed that adding inexpensive milk of magnesia to a more expensive lubricant, such as boron nitride, produced a fluid that exhibits the best properties of both.

Ultimately, the breakthrough technologies Krajewski develops will allow aluminum to be used on a broader range of GM vehicles, not just on the pricey sports cars. "We can now build aluminum vehicles with more 'creases and curves' to excite the eyes of the customer and keep them happy at the gas pump too," he says.

By Diane Kightlinger