The Impact of Electric Racing on Metal Specification Requirements

As the world of motorsport changes with the advent of Electric Racing from Formula E to Endurance Racing and Rally Championships, the requirements for the materials used for Racing Components are changing in ways that surprise many engineers and experts.

Recently, with the advent of the new Gen3 version of the Electric Racing Car by Formula E in 2023, the technical specifications of the vehicle have been released, and interestingly, the weight of the vehicle, including the driver, is 840kg, which is very similar to the weight of a Formula 1 Racing Car. The major difference, however, lies in the type of engine used: one has a screaming V6 engine, and the other has a 350kW Electric Motor and a 51kWh Battery Pack.

Same weight, same requirements, and yet the requirements and the changes made to the vehicle for Electric Racing are quite different from the requirements for the traditional Racing Cars. At Dynamic Metals, we have been supplying aerospace-quality aluminium, titanium, and steel to the Racing Teams for over 25 years. With the advent of Electric Racing Championships from the formation of the FIA Electric Racing Championship in 2014 to the recent announcements made by the FIA regarding the electrification of the Endurance Racing and Rally Championships, we have witnessed the changes made to the requirements for the Racing Components.

What Actually Changes with Electric Racing?

The major changes with the advent of Electric Racing and Electric Powertrains lie in the areas where the weight and the heat are concentrated.

However, thermal loads are merely redistributed and do not go away. Combustion engines have extremely localized thermal loads, with exhaust manifolds at 800-1000°C, turbocharger casings at 950°C+, and combustion chambers at 2000°C+. These extreme temperatures have led to the use of Nickel Superalloys Inconel 718 and Nimonic 80A in exhaust systems and turbocharger casings.

Electric powertrains do away with extreme temperatures, and battery packs, motor, and inverter generate heat during operation. These temperatures are more moderate, with battery packs operating between 20-60°C with good thermal management, rising to 80-100°C under more aggressive use. Electric motor temperatures are at 150-200°C all the time, and the inverter generates a lot of heat in a very compact package.

Weight distribution changes significantly. A Formula E Gen3 battery pack weighs about 280-300kg, which is roughly 35% of the total weight of the car in a single component. For comparison, a Formula 1 power unit (engine, turbocharger, MGU-K, MGU-H, and other ancillaries) weighs about 150kg. This additional weight of 130-150kg needs to be taken care of in other areas to remain competitive.

A new set of structural challenges has to be met. While battery packs are merely that—a battery pack—a battery pack in an electric racing car needs to be a structure that can handle extreme crash loads while keeping the battery cells safe from damage.

Battery Enclosures: The New Critical Structure

The battery pack structure is perhaps the most important use of materials in electric racing cars. They are not merely boxes to contain battery cells and are safety structures that must meet a multitude of conflicting demands.

Strength and crashworthiness are of utmost importance. According to FIA Formula E regulations, battery enclosures must be able to withstand 50g crash forces without battery cell damage. Side crash tests involve 500kg masses moving at 10m/s. It must be able to withstand these forces while protecting battery cell integrity. This is far beyond conventional crash structures, where driver safety is the only concern.

Weight reduction is also of utmost importance. Every kilogram of battery enclosure weight is a kilogram not saved on other parts. With the battery already representing 35% of the vehicle's overall weight, battery enclosure design is optimized to minimize weight while maintaining crashworthiness.

Thermal management integration is also an issue. It must be able to integrate cooling channels, battery cell cooling plates, and battery runaway thermal propagation suppression between battery cells in the event of failure.

Material selection for battery enclosures is usually high-strength aluminium alloys. Our 7075-T6 aluminium alloy, commonly used in aerospace applications, offers high strength-to-weight ratios. It has an ultimate tensile strength of 570 MPa, with excellent energy absorption properties. Its proven record of use in aerospace applications ensures high-confidence performance in high-stakes applications.

6061-T6 aluminium alloy is also used for less-stressed battery enclosure parts where weldability and cost are concerns. While 6061-T6 does not have the same ultimate tensile strength as 7075-T6, 310 MPa is adequate for battery enclosures. It can be used where less stress is applied, and thickness can be used as a variable to compensate.

For high-performance applications, 2014-T6 offers greater ultimate tensile strength than 7075-T6, up to 485 MPa. It has excellent fatigue properties. 2014-T6 has been suggested for battery enclosure mounting points and high-stress attachment points where concentrated forces are applied.

The issue with aluminium battery enclosures is designing joints and interfaces. The welding of high-strength aluminium alloys such as 7075 is difficult and often results in reduced mechanical properties in the heat-affected zone. Many teams use mechanical fastening and adhesive bonding of critical joints and accept the weight penalty for improved joint reliability.

Motor and Inverter Housings: Different Thermal Profile

Electric motors and inverters produce heat during continuous use but at much lower temperatures than combustion-based systems. This changes material selection from nickel superalloys to aluminium alloys that are optimized for thermal conductivity and high-temperature mechanical properties.

Motor housings are expected to operate continuously up to 150-200°C and peak up to 220°C during aggressive use profiles. At these temperatures, aluminium materials retain adequate mechanical properties and offer superior thermal conductivity for heat dissipation into cooling systems.

The 6082-T6 aluminium alloy is highly suitable for motor housings because of its adequate mechanical properties (330 MPa tensile strength) and superior thermal conductivity (160-180 W/m·K) and machinability.

For applications requiring higher mechanical properties—possibly for hybrid applications in which motor housings are also structural members—2014-T6 aluminium offers superior mechanical properties and still maintains relatively good thermal conductivity properties. The higher mechanical properties of 2014-T6 allow for thinner sections, which partially compensate for its lower thermal conductivity compared to 6082-T6 aluminium.

Similar demands are placed upon inverter housings, although thermal management is even more significant in this case. Power electronics can produce high concentrations of heat, and this must be dissipated as efficiently as possible to stop thermal fatigue in semiconductor devices. Aluminium alloys with high thermal conductivity properties become very important in this case, and 6061 and 6082 are again prominent.

The moderate temperatures associated with electric powertrains mean that we won't be using the Nickel Superalloys that are so prevalent in the hot sections of combustion engines. The 180°C environment within the motor housing means that we could utilize Aluminium alloys that would be unable to handle the 950°C environment within a Turbocharger component. This is an opportunity, as Aluminium is less expensive and more readily available than Nickel Superalloys, but it is also a challenge, as designers must be careful not to over-specify these alloys, which are so prevalent in the combustion world.

Weight Compensation: Where Titanium Usage Increases

The 130-150kg battery weight penalty over combustion powertrains puts tremendous emphasis on reducing weight elsewhere in the vehicle.

The suspension components are subject to the same forces in an electric racing car as they are in a combustion racing car. The cornering forces, the braking forces, and the kerbing forces don't care that the power is electric instead of fossil-fuel-powered. The Formula E racing car will still pull 5-6G in the corners, and the suspension will still see forces over 12kN in the braking phases. These forces require the same high-strength material regardless of the power source.

Ti-6Al-4V Titanium, the most popular Titanium alloy in the Aerospace Industry, becomes an even more attractive material in the electric racing world, with a density 45% less than Steel and with strength that rivals many high-strength steels. The 40-50% weight savings that Titanium provides over Steel in the suspension components such as the Wishbones, Uprights, and Pushrods could be considered a welcome bonus in the world of combustion racing, but in the world of electric racing, this weight savings becomes a matter of necessity.

We have a large stock of Ti-6Al-4V bar sections of diameters 25mm up to 100mm, suitable for machining wishbones, upright blanks, and mounting brackets. The fatigue resistance of Ti-6Al-4V is very good and suitable for components subject to millions of cycles over a racing season.

Fasteners are yet another area where titanium is gaining ground. Fasteners add up quickly on a race car. Replacing steel fasteners with titanium alloy Ti-6Al-4V saves 50-60% weight per fastener. For a race car with 2000+ fasteners, this equates to 5-8kg of weight savings for relatively simple substitution.

The problem with substituting large amounts of titanium alloy is cost. Ti-6Al-4V is 6-8 times more expensive per kilogram than high-strength steel. However, where weight savings justify cost, and they increasingly do for electric racing cars, titanium is the obvious choice. Where strength is low, aluminium alloys 7075-T6 offer better cost-effectiveness.

What Hasn't Changed: Chassis and Safety Structures

Just as electric powertrains create new demands, traditional racing materials applications remain unchanged and often more demanding.

Crash structures need to absorb the same impact energy, electric or fossil fuel-powered. The monocoque chassis of a Formula E racing car is built from carbon fibre composite. However, mounting points, fittings, and subframe connections require high-strength metallic materials.

Aerodynamic mounting structures are subject to the same forces. Downforce is downforce, and it doesn’t matter if it is generated by a 1000 horsepower V8 engine or a 350 kW electric motor. Wing mounting pylons, floor supports, and diffuser bracing are subject to the same forces and require lightweight, very stiff materials.

There are no changes in the requirements for the wheel assemblies. The materials that worked for combustion-based racing will work for electric-based racing as well. We continue to see the need for 2618-T6 aluminium for the fabrication of the forged wheel centres, 7075-T6 for the wheel hub, and Ti-6Al-4V for the uprights.

The brake systems have to contend with even tougher conditions. Regenerative braking does most of the braking at high speeds. Consequently, the friction brakes have to do proportionally more work at lower speeds and higher temperatures. The materials required for electric-based racing remain the same as for combustion-based racing. Aluminium for the callipers, titanium for the mounting hardware, and high-strength steel for the pistons.

Opportunities in Formula E and Beyond

Formula E Gen3 specifications have been in place since 2023. These specifications will dictate electric-based racing for years to come. Understanding the requirements will give us an idea of the materials that will be required in the future.

Power output has been raised to 350kW (470bhp), close to F1. Increased power output will put even higher loads on transmission parts. In electric-based racing, transmission parts will increasingly be made of aerospace-grade materials. 300M high-strength steel for gears that have to withstand high loads, Ti-6Al-4V for lighter parts like the transmission shafts because of the moment of inertia, and 2014 or 7075 aluminium for the transmission housings.

Regeneration capability has been raised to 600kW. That is much higher than the power output. Such high regeneration capability will put unique loads on the transmission parts. Parts will have to contend with both driving and braking loads at high magnitudes.

Weight regulations demand a minimum weight of 840kg, inclusive of the driver, with 280-300kg of that weight needed for the battery pack. This leaves approximately 540kg for everything else in a highly competitive racing vehicle. Clearly, every single gram counts and forces manufacturers to use materials with maximum strength-to-weight ratio.

Other forms of motorsport are moving towards electric powertrains too. For example, the World Endurance Championship has a new hypercar class with hybrid powertrains generating over 500kW of total power. Extreme E is a new series for electric SUVs, racing in rally-style events. Even historic racing events are starting to accept electric conversions. Each of these applications demands slightly different materials, but there are some common themes. Thermal management is required at moderate temperatures, weight is optimized where possible, and there is still a need for high-performance materials for safety-critical applications.

Preparing for Electric Racing Materials Demand

At Dynamic Metals, we are monitoring these trends and ensuring our stock holds materials meeting these new demands. We are not abandoning our combustion-based racing materials. We still supply materials for engines for Formula 1, IndyCar, and endurance racing. However, we are increasing our capabilities for electric powertrain-based materials.

Aluminium alloy stock is increasing and includes:

• ·         7075-T6 plate for battery enclosure fabrication
• ·         6082-T6 bar and extrusions for motor housing
• ·         6061-T6 available in various forms for fabricated assemblies and thermal management
• ·         2014-T6 for applications where fatigue resistance is critical
• Titanium stock is increasing for electric vehicle applications too:
• ·         Ti-6Al-4V bar for suspension component sizes
• ·         Diameter rounds for fasteners
• ·         Plate for bracket and fitting components
• High-strength steel is obviously essential for these applications too:
• ·         300M and 4340 steels for high-stressed transmission parts

Maraging steels for extreme-strength applications

Precipitation hardening stainless steels for applications requiring high strength and corrosion resistance

The trick is flexibility. Electric racing is growing, but combustion racing is not going away anytime soon. Formula 1 is still the pinnacle of automotive technology, IndyCar is still successful, and there are numerous national and regional series running combustion engines. They still need suppliers who can deliver on conventional and new technologies alike.

Material Selection Considerations for Electric Racing

There are several factors affecting material selection for electric racing components, unlike those affecting combustion racing:

Operating temperatures are very different. While combustion engines operate at 800-1000°C, electric racing operates at 150-250°C. This does not mean, however, that materials can be downgraded, since component stresses are often unchanged. It does mean, however, that expensive high-temperature alloys are not required. A 6082-T6 aluminium alloy can be used for the motor housing, where an Inconel 718 alloy was required for the turbocharger housing.

Thermal cycling is very different. Combustion engines have very rapid thermal transients, from cold start-up to operating temperature in seconds, followed by numerous thermal shocks during operation. Electric racing, on the other hand, has very mild, but continuous, thermal cycling at temperatures 150-250°C. Weight sensitivity is greater. With 35% of the vehicle weight being batteries, saving weight on other parts gives greater performance benefits. Some materials, while marginally cost-justified in combustion racing, are now clearly cost-justified in electric racing. Titanium suspension parts, while marginally cost-justified in combustion racing, are now obvious choices.

Manufacturing Volume Considerations

With Formula E being a spec series, there are fewer manufacturers producing similar materials. This allows for economies of scale in material and component manufacturing that were not available in Formula 1’s unlimited technical regulations.

With regards to certification requirements, it is possible that battery pack structures will eventually need material certifications beyond traditional racing requirements. This could potentially be on a similar level as aerospace traceability and testing requirements. AS9100 certification, which we already possess for aerospace customers, could become desirable for electric racing suppliers.

The Future: Hydrogen and Next-Generation Electric

Hydrogen and next-generation battery technologies will also drive additional materials requirements for racing applications.

Hydrogen fuel cell racing will introduce corrosion requirements that are not relevant in traditional combustion or electric racing applications. For example, hydrogen embrittlement is a concern for high-strength steels and will be a material consideration for fuel cell systems. Austenitic stainless steels and aluminium materials are more compatible with hydrogen than high-strength materials commonly used in racing applications.

Solid-state battery technology will also be a consideration when it is developed enough for racing applications. Solid-state batteries could potentially offer higher energy density and lower thermal management requirements than existing Lithium-Ion battery technology. This could result in a potential 20-30% weight reduction in battery packs, reducing the weight savings requirements on other materials and components.

Higher voltage systems are also being considered for racing applications. The Formula E Gen3 is already running at 900V, and 1000V+ systems are also being discussed. Higher voltage systems will reduce current requirements for similar power requirements and could result in lighter cable and bus bar requirements. However, higher voltage systems also drive increased insulation requirements and potential arc flash hazards.

The common thread here is that as technology in the powertrain space changes, so do the materials. The basic requirements remain the same – strength, weight, thermal management, and durability – but the relative importance of each changes with the next step in technology.

Supporting Both Traditional and Electric Racing

At Dynamic Metals, we take a pragmatic approach to electric racing, providing materials that support the applications that our customers are developing, regardless of whether the applications are electric or traditional.

Our range of aerospace-grade aluminium alloys, including 2014, 6061, 6082, 7075, and 2099, will support both traditional racing applications, such as suspension, wheel assemblies, and aero, and emerging electric racing applications, such as battery enclosures, motor casings, and inverter components. The material is the same, the applications are different.

Our range of titanium alloys, such as Ti-6Al-4V, will continue to be important to the racing industry, regardless of the powertrain, because of their strength-to-weight properties. The weight issues associated with electric racing create greater demand for titanium than traditional racing.

Our range of high-temperature nickel alloys, such as Inconel 718, Waspaloy, Nimonic 80A, and others, will continue to be important to traditional racing, but will see less demand from the emerging electric racing market, apart from those racing teams that are developing both electric and traditional racing powertrains, and we support both.

What we see as the major advantage to the racing team is that they don’t need to find different suppliers to support their traditional racing program and their electric racing program because we can support both, with the same high standards of AS9100 quality assurance, material traceability, and technical support.

Practical Guidance for Teams Developing Electric Racing Components

For engineering teams developing electric racing components, there are a number of material considerations that need to be considered:

Don't over-specify materials based on experience from the combustion age. The aluminium alloy required for a motor housing at 180°C is probably not the same as that required for an exhaust manifold at 900°C. Don't be tempted to default to known materials when simpler and cheaper alternatives will be adequate. Finally, don't under-specify safety-critical items like battery enclosures on the assumption that electric cars are inherently safer.

Don't forget that total cost of ownership is important, not just material cost. For instance, a material that is more expensive but easier to machine could end up reducing total component cost compared to a cheaper material requiring specialized and costly tooling and slow machining speeds. Ti-6Al-4V is significantly more expensive per kilogram than high-strength steel, but weight savings alone could justify the material cost even before considering machining and assembly benefits.

Don't assume that material properties are as specified in handbooks and catalogues. These are often based on generic test results and may not reflect the properties of the material you receive. Demand certified test results for critical applications. We offer full mill certification with traceable heat numbers on all of our aerospace materials.

Don't plan lead times on materials until you are familiar with suppliers' availability and delivery times. Some materials commonly used in electric racing, such as aluminium alloy and titanium bar in specific sizes and temper grades, could have longer lead times than expected. It is therefore important to contact suppliers at the earliest design phase of your project.

Conclusion

Electric racing is changing the materials demand in motorsport, not by reducing the demand for traditional materials but by adding new demands to those already established. The battery enclosure demands high-strength aluminium alloys for crashworthiness and weight optimisation, while the motor and inverter casings demand aluminium alloys for high thermal conductivity. The demand for weight compensation is also reflected in the increased demand for titanium in suspension and fasteners, while chassis, brakes, and aerodynamic components demand the same high-performance materials as those in combustion racing.

For materials suppliers, the opportunity is serving traditional and emerging applications. For those developing Gen 4 Formula E cars and beyond, they need suppliers who understand traditional requirements for racing structures, as well as new demands for electric powertrains.

At Dynamic Metals, we have been supplying motorsport teams with materials since 1997, serving traditional combustion-based racing structures and emerging electric-based structures. We offer a variety of aluminium alloys for electric racing structures, such as battery cases and motor casings (2014, 6061, 6082, 7075), titanium for electric racing structures (Ti-6Al-4V), and traditional high-strength steels and nickel superalloys for combustion-based racing structures.

Regardless of whether you are designing a traditional combustion-based engine for racing or an electric-based engine for racing, we can supply you with aerospace materials and provide you with all of the necessary information and support for these applications.

Frequently Asked Questions

Q: Does electric racing eliminate the need for high-temperature alloys like Inconel and Nimonic?

A: For pure electric vehicles, yes, as the operating temperatures for the motor and batteries (150-250°C) do not require the exotic nickel superalloys used for the combustion exhaust systems (800-1000°C). However, many racing teams have both combustion and electric vehicle projects, and the hybrid vehicle requires high-temperature components anyway. We will continue to supply our nickel superalloys for the combustion racing community and also be adding aluminium and titanium to our inventory for the electric vehicles. Electric vehicle racing will create a new demand for materials, not replace the existing one.

Q: What aluminium alloys would you recommend for battery pack enclosures?

A: For battery pack enclosures where maximum crash resistance is required, high-strength aluminium alloys such as 7075-T6 with an ultimate tensile strength of 570 MPa would be the preferred choice. For battery pack enclosures where crash resistance is not as critical, 6061-T6 with a lower ultimate tensile strength of 310 MPa would be adequate, as it also offers excellent weldability. Other aluminium alloys, such as 2014-T6 with an ultimate tensile strength of 485 MPa, have also been used for high-stress areas such as the battery pack mounting points and attachment areas. The choice will depend on the specific case and the loads involved. For crash resistance, 7075 would be the better choice, while for weldability, 6061 would be the better choice.

Q: How does the emergence of electric vehicle racing impact the use of titanium versus combustion vehicle racing?

A: Electric vehicle racing will probably increase the demand for titanium due to the weight savings required for these vehicles. The weight of the battery pack, which ranges from 280-300 kg, puts pressure on the designer to save weight wherever possible. Titanium offers a weight savings of 40-50% over steel, which makes it more attractive for these applications. For combustion vehicle racing, titanium is used as an option for weight savings; for the electric vehicle racing community, it will be necessary to use titanium just to meet the weight requirements while still meeting the necessary strength requirements.

Q: Are there any new corrosion and/or environmental concerns with the materials used for the electric vehicle racing community?

A: Compatibility of battery electrolytes will be a concern for materials near battery cells, as in the event of seal failure, the leaked battery fluid should not excessively corrode the materials used in the structure. Most aluminium and stainless-steel alloys have good corrosion resistance. In the future, hydrogen fuel cell racing will bring new corrosion and hydrogen embrittlement concerns that will require careful selection of materials to be used in the structure. In the current electric racing using lithium-ion batteries, there are no major new environmental exposure concerns that have not already been addressed in traditional racing.

Q: How are material lead times different for electric racing versus conventional racing?

A: Material lead times are similar, as both types require aerospace materials with full certification. However, since electric racing is a relatively new industry, there is less standardization of component design, which might require more non-standard sizes of materials than conventional racing. We keep commonly required sizes of aluminium alloys (6061, 6082, 7075) and titanium alloy (Ti-6Al-4V) in stock, which minimizes lead time for both types of applications. Less common sizes or alloy tempers have 8-12 week lead times, irrespective of the application.

Q: Can you assist us with material selection for the electric racing components we are designing?

A: Yes, certainly. Our materials engineering team frequently works with racing teams on material selection for new applications. We can assist you in selecting the best material for your new application. Material selection depends on the operating conditions, including thermal and mechanical stresses, as well as environmental conditions. Once we are familiar with your component requirements, we can suggest the best alloy for your new application. It is best to involve us early in your design phase, as material selection can have significant effects on design, including manufacturing processes, joint design, and heat treatment.