By Andrew Halonen, Mayflower Consulting LLC.
The automotive industry landscape is shifting once again. For the past decade, the industry has seen heavy interest in electric vehicles (EVs), with automotive OEMs making significant investments to convert their vehicle lineup to EVs. However, OEMs are now taking a step back and reconsidering their electrification strategy.1
The shake-up began in the years following the COVID pandemic, when inflation put a squeeze on consumer spending, which resulted in plummeting EV sales. As of January 2025, the White House issued an executive order aimed at eliminating the existing EV mandates,2 with the intention of promoting “true consumer choice.”
With these changes putting pressure on the EV market, OEMs are refocusing their attention on hybrid powertrains that enable low-emission operation, but with a gasoline engine that doesn’t have a refueling challenge. At the same time, OEMs remain steadfast on maximizing the revenue from the sale of internal combustion engine (ICE) vehicles, considering the fact that the cost to produce an EV is much higher, greatly reducing profitability.3 Regardless of the powertrain—electric, hybrid, or ICE — aluminum extrusions bring value to vehicle architectures in several applications. As experience grows, extrusions will continue to become a primary design element in new vehicle design.
Types of Powertrains
The powertrain refers to the engine that powers the vehicle. For 100 years, the market was dominated by ICE powered vehicles using gasoline or diesel. With powertrain dominance came the robust refueling system, with 145,000 public fuel stations across America.4
Then came the hybrid powertrain, which essentially utilizes two power sources — ICE and electric (including a generator, a battery pack, and an electric motor). The electric motor is able to power the vehicle for approximately 30 miles, then the engine takes over. This is more fuel efficient than an ICE alone, because a lot of fuel is consumed when accelerating and in stop/go traffic. The opportunity cost of hybrid is the complexity in having two systems and the associated cost and weight. However, customers appreciate the flexibility, because the hybrid model is able to use gas or diesel as fuel, enabling hybrids to benefit from the expansive gas station network.
Last, the battery or plug-in electric vehicle comprises a very large battery and electric motor(s) to propel the vehicle. EVs have a limited driving range due to the limitations of the battery. In addition, there are only around 61,000 charging stations across the U.S.,5 which are widely spread apart. Therefore, consumers are reluctant to commit to EVs unless the conditions are right (meaning, the EV range and access to charging).
Automotive Extrusions
Aluminum extrusions have long been a part of the vehicle architecture — some are visible and many others hidden under the skin. The visible extrusions include roof racks, bike and ski racks on the tailgate, and running boards. The invisible extrusions are often structural, delivering benefit to the body structure and providing crash energy absorption, stiffness, and torsional rigidity.
The Aluminum Extruders Council (AEC) published a review of automotive applications, which showed that extrusions are found in every area of the vehicle, from front to rear and from roof to bottom.6 The type of powertrain utilized in a vehicle has a significant effect on vehicle architecture and weight balance — and therefore, the selection of materials for various applications. For example, ICE vehicles have significant mass in the front with the engine and transmission, which poses a challenge in maintaining front/rear weight balance. To offset this upfront weight, OEMs may choose to apply lightweight aluminum in the front suspension, brake caliper, and subframe structures, as well as aluminum extrusions in the bumper beams. On the other hand, EVs require the use of battery boxes, which often use an extruded aluminum framework due to its light weight and high rigidity. Meanwhile, some automotive applications are more ubiquitous and are relevant to every type of vehicle, regardless of the powertrain.
Battery Box
The EV is unique in that the energy storage is not a tank full of liquid fuel, rather it is a complex assembly of cells packaged within a box. The fuel is the chemistry of the battery (like lithium-ion), and the energy density is generally about 100 times lower than gasoline.7 Low energy density creates a challenge, making it difficult to pack enough energy into the vehicle to meet the consumer’s desire for hundreds of miles per charge. The Tesla Model Y has 4,680 cells packed tightly for a total weight of 1,700 lbs (771 kg). On average, the weight of an electric vehicle is 1,600 lbs (725 kg) heavier than a similar model ICE vehicle.
Extrusions bring tremendous value to the battery pack. The extrusions surround the perimeter of the pack and are used to carry structural and torsional loads. The multi-hollow extrusion provides energy absorption in the event of a crash. Temperature management is critical in battery packs and the perimeter extrusions also provide a leak-free path for thermal fluids. Finally, aluminum is a natural heat conductor, pulling heat away from the cells to ensure long life.
Figure 1 presents a typical battery box design, showing how the surrounding structure is made with extrusions. The outermost profile is formed with three hollows for stiffness and energy absorption, along with holes for mounting. Inside the battery box is a closed section that likely carries a structural load, as well as fluid transfer to maintain the ideal battery temperatures.
Batteries are a high-value item. The materials are expensive, and safety is imperative. Thermal events must be prevented at all costs. Crash energy from front or side impact needs to be absorbed or deflected away from the cells. From the side, the battery box surround is the last line of defense.
Rocker
The rocker (a.k.a., sill) is the structural support beneath the car doors, and it plays critical function in the protection of the passengers, representing the first line of defense from side impact. A key metric is the rocker’s rupture strength, which is described as the ability to absorb impact energy without breaking. Once a material breaks, the energy passes by and must be absorbed by other structures (such as the EV battery pack). One of the tests of a rocker is the side pole test, in which a car is accelerated sideways into a steel-wrapped concrete pole. The impact is brutal, yet the damage shown during testing of the Tesla Model Y8 seems to be minor.8
Ford converted its flagship F-150 pickup truck to an aluminum body in 2015. This F-150 reportedly has about 80 lbs (36 kg) of extrusions, including a multi-hollow rocker (Figure 2). A decade since its launch, the aluminum F-150 is still holding up well — even in “rustbelt” areas, such as the upper peninsula of Michigan. Each winter, snow piles up and streets are covered with salt to melt the ice. These road salts are brutal on cars and trucks, quickly growing rust, but not on the aluminum-body F150s.
Subframe
The subframe is a structural support for heavy components, such as the engine and transmission in an ICE or the motor of an EV. In addition to carrying a significant load, the subframe is subject to impacts from road debris and corrosion from road salts — an area in which aluminum excels, as shown with the all-aluminum Ford F-150 (as described).
Subframes are commonly made from fabricated pieces in steel or aluminum, but can also be made from a single-piece aluminum casting. There have been subframes made entirely of extrusions that are welded together, as in the Chevy Impala, yet a more elegant solution involves combining aluminum castings with extrusions. An example of this is the subframe in the Audi e-Tron SUV, in which the extrusions act as simple connectors to the cast corner nodes (Figure 3), enabling vibration-absorbing connection points to be combined with many integration features in the profiles.
An advantage of using extrusions during subframe development is the rapid time to prototype, which is just a few weeks. By comparison, the development of stamped steel tooling is closer to 36 weeks, slowing down prototyping. On the other hand, the challenge of using an all-extruded design is the need for extensive welding and the associated labor. Meanwhile, a hybrid subframe that combines extrusions with aluminum castings is a good approach that is cost effective and easy to produce.
Bumper Beam
The bumper beam is the structure behind the plastic bumper cover (Figure 4). The role of the beam is to absorb energy on impact, and to direct the energy load path to joining members. The beam spans side to side, and its connection points are called crush cans or crash cans. These cans are carefully engineered to absorb energy through the combination of an alloy carefully designed to prevent cracking and the specific geometry of the can, which features initiators. The initiators look like a dent in the profile and are designed to initiate the accordion-style crumple that absorbs the crash energy. Aluminum extruded bumper beams are found on a wide variety of vehicles, including the Acura RDX, an ICE vehicle with a body structure that is otherwise almost entirely steel.
Voice of the Customer
A previous article reported the results of a Voice of the Customer (VOC) project, which involved a series of interviews with automotive OEMs, Tier 1 suppliers, and consultants.9 The insights from these interviews included automaker concerns that need to be addressed by extruders, including consistent wall thickness, straightness, integration expertise, alloys, and performance. None of these concerns are related to the choice of powertrain, which means that they apply to all powertrains. For example, long extrusions are used on both battery boxes and rockers alike. The reality is that ease of integration applies to all extrusion applications.
About 75% of aluminum in automotive extrusions is recycled. The impetus for recycled product has been motivated financially to maximize profit. Secondary materials are lower cost than primary aluminum. Today, the push to maximize secondary alloys goes beyond money, and that is under the umbrella of sustainability. OEMs are demanding metal products with increased recycled content without compromising performance. This spurs innovation in recycling from cleanliness to separation of like materials. Pieces of 7000 series aluminum are not desirable in the 6000 series scrap bin, yet it must be identified and separated quickly. Casthouses need to accommodate a larger variance in scrap at different cost structures in order to produce the lowest cost, cleanest aluminum alloy. Innovation is critical to commercialize aluminum materials that meet demanding customer needs.
Conclusion
Over the last few years, the automotive market was so focused on EV design that there were even predictions of ICE vehicles going extinct due to increasing EV sales. Then, the tide turned in reaction to inflation and new government policies. Global OEMs backtracked on their all-EV commitments and began to fill their product pipelines with a mix of EV, hybrid, and ICE vehicles.
Aluminum extrusions are delivering on the promise of efficiency in vehicle design. This efficiency is delivered through the product’s low weight, stiffness, rupture strength, energy absorption, and torsional rigidity. These are critical characteristics in vehicle design that are required to support the powertrain, protect occupants, and provide structural integrity throughout the vehicle. Extruders are listening to customers and innovating in alloy design, process, and integration. The future is bright.
References
- “BriefCASE: OEMs’ balancing act – The resurgence of hybrids as BEVs hit brakes,” S&P Global Mobility, November 27, 2024.
- “Executive Order: Unleashing American Energy,” White House, January 20, 2025, p. 10.
- Root, Al, “GM, Ford Could Have Trouble Selling EVs at a Profit. What It Means for Their Stocks,” Barron’s, May 11, 2023.
- “Service Station FAQs,” American Petroleum Institute.
- Bestvater, Samuel and Sono Shah, “Electric Vehicle Charging Infrastructure in the U.S.,” Pew Research Center, May 23, 2024.
- “Automotive Applications Interactive Guide,” Aluminum Extruders Council.
- Schlachter, Fred, “The Back Page: Has the Battery Bubble Burst?” American Physical Society.
- “2020-2023 Tesla Model Y NHTSA Side Pole Crash Test” (video), CarPro1993 – Crash Test Archive, January 11, 2021.
- Halonen, Andrew, “Extrusions for Automotive – From the Voice of the Customer,” Light Metal Age, June 2024.
Editor’s Note: This article first appeared in the April 2025 issue of Light Metal Age. To receive the current issue, please subscribe.