Alumobility is a global ecosystem that was founded in 2021 to foster collaboration between leading aluminum manufacturers, downstream technology partners, and OEMs, with the aim of supporting the adoption of aluminum in the automotive industry. The three primary members are Constellium, Novelis, and Speira, which work with technology partners on various project studies to develop systems that can make lighter, safer, and more sustainable vehicles.
“What we are trying to do is create a team of people with wide industry knowledge, including our technical partners, like Magna, Atlas Copco, and Fisher,” said Mark White (Figure 1), technical director, Alumobility. “We pool all of this knowledge and resources together into these projects to demonstrate to OEMs that there is a better way of building more sustainable bodies and vehicles for the future. We’re trying to create implementation-ready solutions, so that if an OEM decides to switch from steel to aluminum, we can provide them with all the key enablers to make that happen.”
Automotive Projects
In the three years since its founding, Alumobility has completed six major aluminum conversion projects—all of which showed significant weight saving, while meeting or exceeding automakers’ performance criteria. The first study involved converting a mass-produced C-segment SUV passenger door from steel to aluminum, which showed a 45% weight savings.
This project was followed up with an investigation of a B-pillar, which is one of the most complex components in the vehicle structure due to its importance for both vehicle integrity and safety, and it has traditionally been very heavy. The project successfully demonstrated that shifting from a current steel solution to high-strength 6000 series alloys in the B-pillar could provide a 35% weight savings, while achieving structural and safety requirements. “B-pillars are quite challenging, because there’s a bit of an urban myth that you can’t have an aluminum B-pillar, that it can only be in high strength steel,” noted White. “We wanted to dispel that myth.”
Applying the knowledge garnered from the B-pillar project, Alumobility used the Audi e-tron electric SUV as a reference for a study demonstrating that an aluminum automotive top hat (the upper structure of the body-in-white) can save significant weight compared to steel. The result was a 42% weight savings.
This was followed by the company’s Last Mile Delivery Vehicles (LMDV) project, which focused on the rise of e-commerce. LMDVs are small, lightweight trucks that deliver packages to businesses or residential homes. The study developed an aluminum-intensive LMDV that showed a general weight reduction of up to 22% compared to the steel version, with the aluminum body-in-white alone providing a weight savings of 47%. “We wanted to show there was a better way by electrifying the LMDV,” said White. “By making the vehicle lighter in terms of primary weight savings using aluminum, we could actually reduce the battery size and provide the same driving range.”
For its fifth project, Alumobility was approached by Hyundai Motor Company to conduct a theoretical conversion of the Genesis GV70 electric SUV steel-intensive body to a full-aluminum body. The Genesis GV70 electric vehicle has a mixed-material body structure weighing 385 kg. For the study, the companies converted 285 kg of steel to 171 kg of aluminum, showing a 40% weight savings for the converted parts (Figure 2). In addition, the project focused on optimizing the design to consolidate parts and reduce the type and number of joints required. As a result, the team was able to reduce the part count by 15%, bringing the number of components down from 453 parts in the steel-intensive version to only 386 in the aluminum version (Figure 3). It also minimized the amount of spot welded joints to only 4,575 (a 25% reduction from the steel reference), with SPR joints reduced to only 1,935.
Most recently, Alumobility partnered with Porsche to complete a theoretical case study focused on converting the existing steel-intensive, mixed-material body top hat structure of the Porsche Taycan all-electric sports car to an all-aluminum top hat. This aluminum design conversion showed an approximate 40% weight savings against the steel reference parts, while also maintaining attributes for safety, body stiffness, and performance. The project further demonstrated that aluminum-intensive vehicles offer manufacturing efficiency opportunities by reducing the number of parts, joint types, and total joint count. In addition, it was determined that the use of recycled aluminum would lower lifetime emissions compared to the steel reference.
Aluminum Conversion Method
When considering which vehicle to focus on for their conversion studies, Alumobility aims to address the kinds of projects that will be most relevant to OEMs. In many cases this involves projects where lightweighting can have the most impact in terms of efficiency and driving range, which includes but is not limited to SUVs and electric vehicles. SUVs are the biggest selling segment, and their large size provides ample opportunity for reducing weight. Electric vehicles tend to be heavy due to their large battery packs and reducing weight helps to improve driving range.
Once a vehicle model has been selected, Alumobility begins by setting some targets. Generally, this involves at least a 40% weight savings across the body and major chassis components, while providing the same performance as the steel version. This 40% target is key, as it provides enough of a primary weight reduction to allow for secondary weight savings in other areas of the vehicle (for example, a smaller battery pack). Additional goals might include consolidating parts, reducing gauge-grade complexity, and/or joint reduction (such as on the Hyundai project, which had a target of reducing the required amount of joints by 20%).
The actual conversion process is divided into three main stages. Alumobility begins with the straight conversion process, in which they take the steel reference parts and use a set of value equations to make a direct conversion. For a basic structural part, a conversion factor of 1.45 is used, which means that if the steel part is 1 mm thick, then the aluminum part will be 1.45 mm thick. This typically provides an automatic weight savings of over 50%. Different components require different conversion rates, such as with stiffness- or strength-dominated parts, particularly if they use advanced high strength steel or ultra-high strength steel. In this case, the conversion factor might be in the range of 1.7–2.
“The big challenge for aluminum is to replace the ultra-high strength steel parts, such as B-pillars, A-pillars, and some of the structural members,” said White. “We relish those challenges, because we can take those parts and present aluminum solutions that meet or beat the performance of steel. For example, with components for roof crush protection, we believe that aluminum has an advantage, because aluminum absorbs more energy per kilogram than steel. Given the right grade and gauge, aluminum should be able to better absorb the impact during a crash, and these types of projects help to prove that. I don’t think it’s any coincidence that we’re seeing more and more crash structures in production cars, like the Ford Explorer or the BMW X5, where the whole front end of the car is being replaced in aluminum.”
Once this initial conversion is complete, Alumobility performs a hygiene check to make sure the weight and performance goals are met. Then, they begin the second stage, which involves combining and/or simplifying parts, reducing the number of joints, and designing the car to be optimized for the aluminum concept. This also includes a check of the feasibility of the design (in terms of joining and manufacturing) and the quality of the components.
“We think this is a key enabler for OEMs to switch from steel to aluminum,” noted White. “By using aluminum, we can actually make the vehicle body simpler and more straightforward to assemble and manufacture. A great example is the Hyundai GV70, which is a mixed-material car. It already used some aluminum, which required special joining technologies to join the aluminum to steel, such as a sealer to prevent any bi-metal corrosion. We think that by applying a less is more strategy, we can lower CAPEX and OPEX costs compared to either a mixed-material body or even a conventional steel body that uses advanced and ultra-high strength steels, which in themselves require special joining and stamping technologies.”
The final stage is to recheck the performance attributes of the aluminum design using the latest simulation techniques. The team looks at the steel reference baseline and then makes sure that the aluminum conversion meets or improves upon the performance for aspects such as stiffness, strength, front crash, side crash, etc. White explained, “To put this in context, with the GV70, we showed aluminum could increase torsional stiffness by 29% and bending stiffness by 6%, which is a considerable improvement over the steel baseline. So, we not only made the car as safe as the steel baseline, but have actually made it stiffer from a performance point of view.”
Although Alumobility was founded by aluminum sheet companies, it’s important to point out that the company focuses on choosing the right manufacturing process for the right application. Castings are often the best option for applications such as front shocks in suspensions, while extrusion profiles are often the best for bumper beam assemblies because of their long profile and crush box capabilities. “None of our studies are 100% sheet,” said White. “They all have a mix of stamped sheet, roll forming, casting, and extrusion. We don’t believe in being prescriptive. We want to use different forming processes, alloys, and joining techniques to show there are multiple ways of doing things, so that we can provide OEMs with a choice. If you look across our projects, they all use a recipe that is bespoke to the OEM in terms of their types of vehicles and volume requirements. This is the best way to demonstrate that aluminum is the material of choice for future sustainable transport.”
Shifting Away from Mixed Materials
The automotive industry was dominated by steel vehicles up until the ‘90s. Then, certain manufacturers, such as Jaguar and later Audi, began to introduce examples of all-aluminum models. According to White, these vehicles were a signpost to a future in which all cars could be made out of aluminum. The steel industry responded by developing more and more advanced and ultra-high strength steels, shifting from four steel grades a couple of decades ago to over 65 grades now. “If anything, it was quite substitutional and cannibalistic, because they just kept replacing one steel grade with another steel grade,” said White. “Then, the steel industry ran out of steam a little bit, and OEMs began looking at combining the benefits of lightweight aluminum with the ultra-high strength steels for strength.”
As a result, a major trend from 2010 to the early 2020s has been a focus on utilizing mixed- or multi-material construction, with automakers selecting the “right material for the right part.” Vehicles using this method may utilize a combination of steels, aluminum, magnesium, composites, and other materials. According to White, this had an unintended consequence. “They drove a lot of complexity into the manufacturing environment,” said White. “At the time, the manufacturing guys really didn’t know what was coming at them, but once they built a few mixed material cars, they realized the problem, finding that they had gone from two or three joining technologies originally to over twelve in some mixed-material cars. All of these joints have to be isolated, and in the press or body shop, they have to be careful to avoid cross-metallic contamination.”
This problem of complexity is causing many automakers to shift back to single-material designs. If they want to save weight, the OEM might put aluminum closures (such as doors, hoods, liftgates, etc.) on a steel car. Or, in some cases, they might shift to a full aluminum top hat or even all-aluminum body-in-white, such as the Ford F-150 or Lucid Air.
“You don’t hear many people saying the right material in the right place anymore,” explained White. “People better understand the penalties of mixed material now. Most people are of the view that it’s better to either make it steel or aluminum, and try to keep the interfaces between the two materials down to the absolute minimum, rather than mixing and matching.”
Moving Forward
After three years, Alumobility has continued to learn and grow from its previous projects. According to White, the company is currently working with another OEM on a seventh project that is expected to be completed in 2025. “The new project really encompasses everything we’ve learned from the previous projects and all of the knowledge and skills that we’ve built,” he said. “This is going to be our biggest project to date, and it’s going to show the real power of aluminum.”
White believes this is important to addressing the issue of vehicles continuing to increase in weight, despite the lightweighting technologies available. Heavier batteries and more technologies (such as entertainment systems or automated driving) increase the weight of the car, which results in compounding. For example, heavier cars need bigger brakes to bring the vehicle to a stop. Heavier cars also bring more energy into a crash, which means that the crash structure needs to be upgraded.
“Our cars have been getting heavier and heavier,” said White. “Imagine if we could reverse that weight cycle by mass decompounding. If we take enough mass out of the body and chassis using aluminum, we can actually reduce the size of the motors, battery pack, brakes, and other components. We could transform that negative weight spiral into what I call a virtuous spiral. That’s really where I’d like to get to with the next project and beyond—to show that we can make cars lighter, more sustainable, and more attractive to both the OEM and the customer.”
Editor’s Note: This article first appeared in the June 2024 issue of Light Metal Age. To receive the current issue, please subscribe.