Lighten Up: Aluminum Advances
There are two poster children for the use of aluminum in automotive applications that have appeared during the past few years. First off, there’s the 2015 Ford F-150, the truck with “high-strength, military-grade alloy” in its body, material that contributes to a mass reduction of up to 700 pounds for the vehicle overall, which translates into features including the ability to tow up to 1,100 more pounds and haul 530 more pounds because the powertrain doesn’t have to move as much vehicle mass. The F-150 application of aluminum has worked out fairly well for Ford, apparently, as the company not only decided to use the material for the 2017 Super Duty—and know that this is the first-ever redesign of that truck—but aluminum is also being used for the body of the forthcoming 2018 Expedition.
Before looking at the second vehicle, a word about that 2017 Super Duty, as it makes an important point that we’ll get to later. In addition to the aluminum for the body applications, the truck’s boxed frame is made with more than 95 percent high-strength steel. (Yes, the frames of the F-150 and the Expedition are also made with steel.)
The second poster child is the 2016 Cadillac CT6 sedan. For that car, 64 percent of the body structure is aluminum, including all of the body panels. To assemble that car they’re using aluminum spot, laser and arc welding, as well as an abundance of adhesives. There are high-pressure aluminum die castings. There is a high-strength aluminum impact bar in the rear of the vehicle.
In all, there are thirteen different materials used for the construction. The utilization of different materials allows the car to be, they’ve calculated, 198 pounds lighter than a steel-intensive vehicle would be. Mass reduction was of particular interest to the CT6 engineering team not only because they wanted superior ride and handling (lighter is certainly better than ponderous), but because they knew that there was a plug-in hybrid coming (it is introduced as a 2017 model), and when you are using electricity to move a vehicle, you want to make sure that the mass is optimized. (Arguably, the Tesla Model S could be considered a poster child for aluminum vehicles, but people can’t get over the electric powertrain so its structure and skin are typically overlooked.)
John Thomas, director, Global Marketing–Automotive, Arconic (arconic.com), is certainly pleased with those vehicles because his company supplies aluminum for them. And it also supplies a multitude of other OEMs with material, and has been, in many cases, for a number of years, particularly as sheet for closure panels. “Closures,” he says, “are a natural fit for aluminum. OEMs have been making aluminum hoods for decades.”
Which goes to the point of experience in terms of processing the material in the factory. It is nothing new. That said, Thomas points out that they’ve developed a technology, “Micromill,” that allows the creation of next-gen aluminum alloys that are as much as 40 percent more formable than what has traditionally been the case, thereby expanding the opportunity for use of aluminum in more expressively shaped closure panels. Thomas acknowledges that “formability is key” when it comes to OEMs, and adds that “styling is huge.” As are, of course, lightweighting and safety.
To the point of formability, he points out that while traditionally it has been thought that if a deep draw is required, such as for a door inner, steel was the way to go, that is no longer the case. Consequently, it is possible to create doors where both skin and structure are aluminum.
While it seems that B-pillars have become the realm of hot-stamped steel, Thomas points out that they’ve developed aluminum alloys that can be used for the application—and notes that the B-pillars in the F-150 are made with aluminum.
Another development that Arconic has made to facilitate the use of aluminum is a pretreatment, Arconic 951. Thomas explains that this coating allows joints that are, say, adhesively bonded and riveted to have greater bond durability—as much as nine times greater—than aluminum coated with materials like titanium-zirconium.
Yet proponent of aluminum as he is, Thomas recognizes that there is a likelihood for more mixed-materials in vehicles than just one, especially in cases where the vehicles are more mainstream than, say, a Jaguar XF. “There are more choices in material at the buffet table than there ever has been.” He adds, “It’s not an all-or-nothing proposition.”
“We have people designing for aluminum rather than just replacing steel with aluminum,” Thomas says.
“Could it change the slope of application of aluminum in the future? Sure. But what’s not changing is the slope for content, for pounds per vehicle”—and he notes that in addition to sheet, there are also things like aluminum extrusions and castings—“will continue to go up.”
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