DALLAS — Alcoa is touting a breakthrough in aluminum manufacturing that it says will give the lightweight metal a better chance to replace steel in car doors and fenders.

Alcoa says the process, still in the testing phase, will create metal sheets that are stronger and more easily shaped into auto body parts than current aluminum and are lighter than steel. Company executives say the aluminum-alloy material could show up in cars by 2018.

Alcoa said Thursday that it has conducted successful tests with automakers and has lined up one as a “strategic-development customer” for aluminum being produced at a pilot mill in San Antonio, Texas. Alcoa declined to name the other companies.

Alcoa has been shifting from mining and smelting aluminum to making products that can be shaped into parts for autos and airplanes. It has made inroads in automaking, where the use of aluminum has been growing for years to produce cars that are lighter and get better mileage.

Now Alcoa is taking aim at steel’s $1 billion annual market in doors and fenders. It got a boost when one of its customers, Ford, decided to make the 2015 model of its F-150 pickup with a body that is 97 percent aluminum. That shaved up to 700 pounds from the 5,000-pound truck.

Aluminum has been used extensively on some sporty but relatively low-sales cars such as the Tesla Model S. Some analysts believe that Ford’s decision to clad the popular F-150 in aluminum threatens steel because it shows that lighter materials — and not just smaller vehicles, which some consumers don’t like — can be used to meet tougher fuel-economy standards.

Alcoa CEO Klaus Kleinfeld said in an interview that automakers tell him they want lighter materials without sacrificing safety or steel’s ability to be shaped into car designs.

“We knew there were some hills that aluminum had yet not climbed and that were occupied by steel because of the formability,” Kleinfeld said. “We needed to reinvent a breakthrough production technology.” Kleinfeld added Alcoa has 130 patents on the new technology.