Phil Martens of Novelis: “Aluminum has emerged with production models as a viable structural and body-in-white material that can reduce the weight of a product.” And as regulations for fuel efficiency and emissions become more demanding, the material becomes more of a consideration, Martens suggests.
The Jaguar XJ is an aluminum-intensive vehicle. Design director Ian Callum says that he has a close working relationship with the Jaguar body engineering staff so that designers can push the forms and the people in manufacturing can actually produce them.
The Jaguar XJ is bonded and riveted, not welded. An interesting aspect of the architecture is that this is a unibody structure, similar to that used for steel-based cars.
The Audi A8 was developed so that it is a light vehicle for its size, and consequently makes extensive use of aluminum.
With his extensive engineering background in the auto industry—he was group vice president of Product Creation at the Ford Motor Company, president and CEO of Plastech Engineered Products, and senior vice president, Light Vehicle Systems, ArvinMeritor, and president and CEO designate of Arvin Innovation—Phillip Martens is ideally positioned to assess the application, the potential, and the challenges to the implementation of aluminum in automotive. And as he is president and COO of Novelis Inc., an $11-billion global company in aluminum rolled products, his opinion while, perhaps biased, is certainly an informed one.
While one might think that the decision to use a particular material for body, structural or powertrain applications would be largely driven by straight-up engineer-ing and financial considerations, Martens points out that there is another huge driving factor: Government regulations. And he's talking about government regulations that are in place or scheduled to kick in not only in the U.S., but around the world. These are external factors that loom large as vehicle manufacturers try to sort out the appropriate strategies.
For example, he points out that the European Union set CO2 emissions standards in the early 1990s. A result of this was that European vehicle manufacturers had to change their emissions strategies, which led to changes of various types, such as the greater deployment of diesel powertrains, downsizing the fleet, and the use of aluminum for body-in-white applications.
Speaking of what's happened in Europe, Martens says, "Aluminum has emerged with production models as a viable structural and body-in-white material that is a manufacturable solution that can light-weight a product." But he acknowledges that it became a choice predicated on external factors, factors that he thinks are going to be faced by North American vehicle manufacturers. For example, trying to meet the CAFE regulations that call for car average fuel efficiency of 37.8 mpg and light truck fuel efficiency of 28.8 mpg for a combined 34.1 mpg by 2016 is going to require some changes in approach, which very well may include the deployment of greater amounts of aluminum. "As regulatory requirements increase, other options become more relevant," he says.
He admits, however, "I think it is a case-by-case situation," not a foreordained solution. "Aluminum is always on the table as a choice, but it has to pass muster," he says, then ticks off a number of requirements—from cost to manufacturability to performance to customer acceptability—that must be met. But he points out that experiences by other global vehicle manufacturers—and he cites, for example, that Novelis is a supplier to Jaguar's aluminum-based bodies-in-white, including the new XJ—provide evidence of the viability of aluminum. Speaking of Jaguar, he says, "They can style it, make it economically viable in the market, and achieve significant fuel economy improvements and emissions reductions with aluminum."
The Jaguar Approach
Speaking of the design of the new XJ and its appropriateness luxury category vis-à-vis the heightened global concern for things like a carbon footprint, Ian Callum, Design Director, says, "The secret is not the size of the car"—the overall length of the short-wheel-base XJ is 201.7 in.; it is 206.6 in. for the long-wheel-base version—"but the mass of the car." The short-wheel-base model weighs from 3,870 lb to 4,172 lb, depending on powertrain; the long-wheel-base versions range in curb weight from 3,909 to 4,223 lb. "This car is extremely appropriate because it is made of aluminum. It is the lightest car in its class, by far." In other words, it has the size of a full-size luxury car with the mass of an executive car. The XJ weighs on the order of 300 lb. less than a comparable steel vehicle.
"Jaguar has probably become the most-advanced aluminum auto body maker in the world," Callum claims. "We've made a step-change with this car." And while he acknowledges that his competitors at Audi certainly know their stuff when it comes to building aluminum cars, he suggests that whereas their approach is "skeletal"—the ASF, or Audi Space Frame, has an aluminum structure upon which body panels are affixed—the XJ is a unibody vehicle, much more analogous to a steel-bodied car.
Yet Callum isn't blasé about what they're accomplishing for a number of reasons. For one: "It is hard work." For another: "Aluminum is expensive."
About the first, he says that he and Mark White, Jaguar's chief technical specialist for body engineering, spend a considerable amount of time working closely together. Callum's designers are pushing what they want in terms of the style and dynamic excitement that are characteristic of contemporary Jags; White's engineers are pushing the boundaries of what can be achieved in terms of forming aluminum.
For example, the doors of the XJ have a one-piece design compared with the three pieces used for the previous-generation XJ, which was introduced in 2003. The new XJ also utilizes high-strength aluminum alloys in areas like the roof pillars and door openings to enhance overall body stiffness.
"There are radiuses in this car that I would like to be a little bit sharper," Callum says. And he points out that the draws you can make in aluminum are not as extensive as those that can be achieved in steel. He cites the steel "monoside" of the XF, "a big draw across the haunch. I doubt that we could do that today in aluminum. It would probably take two pieces with a joint, which would be expensive." Form-wise, they're unable to get everything with aluminum. "But you accept it for what it is." He adds, "I like the texture the aluminum creates, its own visual values." And he says, speaking of the XF, "At some point we will do an aluminum one."
(It should be noted that Jaguar has not-inconsiderable experience in building aluminum cars, as it made its first in 1948, the XK120 roadster.)
As for the second, the expense of aluminum, Callum points out that 50% of the aluminum body is recycled material. Consequently, this reduces the amount of energy required as compared with new aluminum—only about 5%—which reduces the carbon footprint. And it is less expensive. What's more, he says that they're planning to expand the amount of recycled material to 75%, then 90%. Which certainly is beneficial as regards the material cost and the environmental impact.
Callum also comments that the manufacturing operations in the Castle Bromwich plant are different than those found in most assembly plants in that the XJ body is robotically bonded and riveted, not welded. Compared with the previous XJ, the number of rivets used is down by 11%. This not only means reduced vehicle mass, but it also has a positive effect on electricity use. What's more, as rivet guns don't need cooling water like spot welding guns do, there is reduced use of water, as well.
But what about alternate materials? Callum notes that they are using a one-piece magnesium casting in front of the engine (the engines have recycled aluminum blocks and heads), the aperture. Plastics and composites? Callum says that they've looked at polymers for such things as hoods and decklids, "but for us, aluminum is easier and light. It is hard to get lighter than aluminum." As for composites, he says, "I'm sure we will use composite materials," but adds, "The piece cost of carbon fiber is exceedingly expensive."
Lighter Is Better for EVs
One of the biggest barriers to the wide-scale launch of electric vehicles (EVs) is the comparatively high cost of the batteries. So it might seem odd that one would use aluminum for vehicle structures as the material is more expensive than steel, right?
Well, clearly the people at The Aluminum Association (aluminumtransportation.org) figured that that might be the case, so they contracted with the engineering firm Ricardo (ricardo.com) to run a study on the use of aluminum for EVs (plug-in battery powered and plug-in hybrid). The results indicate serious money can be saved in vehicle cost through the use of light-weighting the vehicle structure with aluminum.
“What this new report shows is that by upgrading from traditional steel to an advanced aluminum body structure, the vehicle’s stored energy requirements can be cut by about 10 percent, which could save up to $3,000 per vehicle since less power and energy is required to move the lighter vehicle.” So said Michael Bull—director of Automotive Technology for Novelis—on behalf of The Aluminum Association.
The study looked at 16 vehicles or variants, both small cars and small SUVs, full EVs as well as plug-in hybrid EVs, 40- and 80-mile ranges, aluminum and steel structures.
The issue is the most efficient use of the energy stored in the battery. Reducing the mass of the vehicle means there is less to move. And there was a correlation found: reduce vehicle mass by 20% and go 20% further. One of the vehicles in the study showed a range extension from 80 to 97 miles through the use of the aluminum structure that permitted mass reduction.
Aluminum Sandwich & the A8
Novelis has developed a new process that allows the creation of aluminum alloy sheet materials that has more than one alloy: essentially, it creates a “sandwich.” Called Fusion, multiple alloy layers are simultaneously cast, then the resulting ingot is rolled into sheet. This allows material characteristics to be tailored to the application—strength, corrosion-resistance, etc.
Novelis has been named the lead aluminum sheet supplier for the fourth-generation Audi A8. Applications on the vehicle include the hood, decklid, doors, and roof. In addition to which, the floor tunnel will be produced with Fusion AS250 sheet instead of a dual-phase steel.