As the government pushes the automobile industry to develop greater fuel-efficiency in marches toward the 54 mpg CAFE mandate, competition increases among high-strength steel, carbon and aluminum to overcome the obstacles of physics.

The New York Times says more efficient engines and electric powertrains can’t carry the whole load, so carmakers and the federal government are pouring resources into “lightweighting” auto platforms to meet the Corporate Average Fuel Economy, or CAFE, standards.

Right now, advances in aluminum are at the forefront. GM recently annpunced that it has invented an industry-first aluminum welding technology that it expects to enable more use of the lightweight aluminum on future vehicles.

GM’s new resistance spot welding process uses a patented multi-ring domed electrode that does what smooth electrodes are unreliable at doing – welding aluminum to aluminum. By using this process GM expects to eliminate nearly two pounds of rivets from aluminum body parts such as hoods, liftgates and doors.

GM already uses this patented process on the hood of the Cadillac CTS-V and the liftgate of the hybrid versions of Chevrolet Tahoe and GMC Yukon. GM plans to use this technology more extensively starting this year.

The ability to weld aluminum body structures and closures in such a robust fashion will give GM a unique manufacturing advantage,” said Jon Lauckner, GM chief technology officer and vice president of Global R&D.

“This new technology solves the long-standing problem of spot welding aluminum, which is how all manufacturers have welded steel parts together for decades,” Lauckner said. “It is an important step forward that will grow in importance as we increase the use of aluminum in our cars, trucks and crossovers over the next several years.”

Spot welding uses two opposing electrode pincers to compress and fuse pieces of metal together, using an electrical current to create intense heat to form a weld. The process is inexpensive, fast and reliable, but until now, not robust for use on aluminum in today’s manufacturing environment. GM’s new welding technique works on sheet, extruded and cast aluminum because GM’s proprietary multi-ring domed electrode head disrupts the oxide on aluminum’s surface to enable a stronger weld.

Ford, meanwhile is using carbon fiber in certain niche applications, like an inner-engine hatch cover for the Ford GT supercar and a hood for the Shelby GT500KR. Earlier this year, the company announced that it was collaborating with Dow Automotive Systems to develop lower-cost carbon fiber composites for mass production. It estimated that 750-pound weight reductions were possible, according to a NY Times report.

Steel is making gains too... The American Iron and Steel Institute's Ron Krupitzer says "“The steel available for car companies now is up to five times stronger than the steel used 10 years ago. A part that weighed 100 pounds is being replaced by one that’s 75 pounds, with no price increase.”