Guest commentary: Materials science advances can move carmakers beyond steel

The combination of new safety standards and tougher emissions standards has left auto manufacturers between a rock and a hard place.

NHTSA sets corporate average fuel economy standards, which regulate fuel efficiency. In July, the nation's top safety agency proposed a change that, if finalized, would require a fleetwide industry average of around 58 mpg for passenger cars and light trucks by 2032, an increase of 2 percent a year for cars and 4 percent a year for light trucks.

These standards have intensified the industry's focus on lightweighting as the quickest way to improve fuel efficiency.

At the same time, NHTSA's crash test requirements are getting stricter. Smaller, lighter, more efficient cars don't offer as much protection in crashes, especially to rear seat passengers. Traditionally, improving crash test results means adding more steel — but more steel equals a heavier vehicle.

The way out of this quandary is through materials engineering. Materials engineering is increasingly becoming an area of interest for automakers, as many applications of advanced materials that were once niche — such as parts for small-volume cars and racing vehicles — are now being scaled up and used on high-volume vehicles.

The quest for lighter-weight vehicles has led to an increased use of aluminum in automobile manufacturing.

In 2020, aluminum was the fastest-growing automotive material, a trend that's expected to continue. A turning point in the transition was when Ford made the bold move to use an aluminum body for its F-150 pickup in 2015. Truck bodies had always been made of steel, for many reasons: Consumers weren't keen on pickups made of the same materials as soda cans, plus aluminum was more difficult to repair because auto shops are set up to work with steel parts. So when Ford made the switch, there was an outcry and some name-calling — but the F-150 remains one of the bestselling vehicles in the U.S. Other manufacturers have followed.

Advances in materials science have enabled the use of large-scale aluminum castings to create what traditionally would be many separate parts welded together. The result is a single, much lighter cast aluminum part that frees up weight for high-strength steel on crash-critical components. This process is relatively new and largely pushed by Tesla, though several automakers are looking at how to adopt large-scale castings like this.

Magnesium is another example of materials innovation entering the mainstream auto market. Historically, magnesium was reserved for niche parts, such as wheels on race cars. But advances have led to its use in certain Jeep tailgates.

Jeep owners tend to carry huge spare tires, which have to be bolted onto the tailgate without warping it. At the same time, the tailgate can't be so heavy that a driver is unable to open it. Magnesium provides a material stiff enough to support the weight of a heavy tire but lightweight enough to function as a tailgate.

Though the switch to aluminum for many parts is well underway, advanced high-strength steels, or Gen3 steels, also have untapped potential for auto manufacturers. Gen3 steels were preceded by dual-phase steels, which involve two phases of steel combined to create an alloy that is strong and formable. But dual-phase steels are difficult to form into deep drawn geometries.

The promise of Gen3 steel is that it offers the benefits of high-strength steel with the formability of a milder steel.

Gen3 steel allows a part to be made entirely of the same material, whereas dual-phase steel had to be manufactured as multiple pieces that were then welded together. Similar to large-scale aluminum casting, something that would have been 20 or 30 separate stampings joined together can now be formed as one part using Gen3 steel.

It's faster, cheaper and stronger. It improves the entire process of car manufacturing and provides lightweighting opportunities while adding to safety.

Getting the desired properties out of steel requires very complex chemistry along with complex post-casting processing and heat treatment. The digitization of materials science makes that process achievable.

Whereas previously, designing a material with the desired properties involved a great deal of trial-and-error, digital tools can now predict material performance, helping engineers greatly narrow the field before experimentation. These tools can also help to predict variation in properties as production scales, and identify potential weaknesses in the production process.

In industries such as aerospace, manufacturers that leverage novel materials obtain a competitive advantage and unlock new heights of performance.

Automakers facing simultaneous pressure from efficiency standards and safety requirements have little choice but to do the same.