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Latest Trends for Aluminium Demand in Automotive Industry

| Author / Editor: Goran Djukanovic / Daniel Richter

Although Aluminium in automobiles has been used for several years its proportion in new vehicles increases steadily. Nevertheless, the use of aluminium adoption in automobiles and demand varies from country to country for various reasons.

Lightening of vehicles must be done without compromise regarding safetey before all, quality, and performace.
( Source: Pixabay / CC0 )

During the last several years aluminium use in automobiles and light trucks marks the highest growth from all other aluminium applications, in any segment of use. Aluminium remains “the fastest growing automotive material over competing materials and is entering its most unprecedented growth phase since we’ve been tracking the shifting mix of automotive materials,” the latest survey of automakers by Ducker Worldwide (U.S. leading consultancy) showed.

The WardsAuto and DuPont Automotive survey also confirms aluminium is the first preferred material of choice among engineers and designers to help meet the expected fuel economy and emissions standards by 2025.

Additional prospects for even higher aluminium demand comes from electric vehicles revolution, entering the market sooner and faster than anyone could expect. In the electric vehicle (EV) market, the biggest factor that drives consumer preference, aside of high but falling costs, is driving range. To achieve a high range for a given battery size and weight, weight reduction of EV is needed. And again, the preferred material in EV lightening is aluminium.

The e-Golf has 129 kg of aluminium and the Leaf uses 171 kg while Tesla’s luxury Model S contains 661 kg of the metal, according to A2mac1 Automotive Benchmarking.

Sales of electric and hybrid vehicles are due to surge to 30 % of the global auto market by 2030, according to metal consultants CRU, up from 4 % of the 86 million vehicles sold last year.

CRU also predicts demand for aluminium from electric and hybrid vehicles is to increase ten times to nearly 10 million tonnes by 2030.


Lightening of vehicles spurred demand for aluminium

All future automobiles will need to satisfy stringent emission standards and the best way to do it with exciting technologies is to reduce their weight. Various aluminium alloys, all kinds and generations of advanced high strength steels, then magnesium, composite materials (carbon fiber) and various plastic materials are the main to be used in automobiles to achieve that goal. Parallel with new types of alloys new techniques of material shaping/designing are established and used.

Lightening of vehicles must be done without compromise regarding safetey before all, quality, and performace. It is neccesary to be efficient, funcional lightening – meeting fuel emission guidlines. And preferably not too much costly.

The combination of strength with ductility is the key performance parameter for automotive applications.

Although aluminium in automobiles has been used for more than two decades, mostly in engine and power train castings and wheels, meaning cast parts and extrusions, the new aluminium sheet alloys and new production and assembling (welding) techniques will enable significant increase of aluminium sheet use in most selling automobiles and not only in luxury models.

According to Ducker Worldwide, between 2015 and 2020 the average vehicle in North America is expected to lose 100 pounds (45 kg) thanks to lightweighting. Aluminium will account for 57 % of that loss. Advanced high strength steels will account for 40 %.

Aluminium and AHSS content as percent of vehicle curb weight to rise

The main battle for a position in future cars is lead between aluminium and steel. The latest outcome is that aluminium is advancing and increasing its content in cars while steel, with its advanced high strength steel (AHSS) variations is defending its still dominant position.

Aluminium content in cars is increasing with fastest pace and highest quantity per car in North America.

The first step in vehicle lightening can be done by use of advanced high strength steels, but there are limits to that. For big weight savings is needed lighter material, while aluminium is an optimal solution. So aluminium will be used in big cars (SUVs), while AHSS will most likely keep its dominance in small cars.

Economic development of a region (country) is fundamental driver for aluminium demand in automotive industry, but and other lighter materials, including AHSS, replacing mild /conventional steel. The geographic position will also have influence on favouring of aluminium or steel use. While aluminium will gain in quantity over steel in new car models made in Europe and North America, shifting to aluminium in Asian markets will be more slowly due to the costly process of change and less strict fuel emissions standards. However, the highest production growth of automobiles will occur in Asia with China the biggest producer in the world.

Weight reduction potential

Some key components, where increase of aluminium use will be the highest are:

Closures (the highest by weight – doors, hub, back trunk), then shock towers, other body and closures, while by percentage the highest increase in use will be at subframe and crossmember, bumpers, body extrusions and other body castings. Decrease of aluminium content will occur in motor – block and head.

With the exception of a few critical areas, such as: roofrail, longitudinal front and upper, aimed to improve critical points and safety of passenger cabin, it is now possible to make an entire body-in-white from aluminium, resulting in significant weight reduction and performance increases.

Since its lower density, aluminium components in cars are thicker compared to the AHSS components for the same purpose and for most of components the ratio is 1.5 : 1 (Al alloy vs. AHSS).

The combination of strength with ductility is the key performance parameter desired for automotive applications. However, the relationship between the material properties and the strength, stiffness and weight of a component is very complex and can be strongly influenced by geometry of the part, meaning that there is no absolute rule. Moreover, there are limits to what can be achieved – traditionally, higher strengths come at the expense of ductility. There are ways around this – hot stamping, or additional heat treatment cycles – but the technology required can have significant effects on both cost and production cycle time.

Aluminium extruders are developing new types of 6000-series aluminium alloys for automotive applications that require higher strength, such as bumper systems, crash boxes, and side sills. Started in 2017, new alloys could serve as an alternative to high-strength 7000-series aluminium alloys but easier to extrude and at lower cost. New alloys can achieve similar tensile yield strengths to 7000 alloys.

Al alloy 7075 – T6 is used, for instance, at the 2014 C7 Corvette Stingray from General Motors at the front crush-zone,the extrusion that is made from a high-yield, high-strength 7000-series aluminium alloy. It folds up like an accordion during a collision to absorb the impact energy, claim GM engineers.

Reduction in mass of 10% reduces fuel consumption for 6.5 %

100 kg mass reduction achieved on a car reduces 8 grams of CO2 per km at the exhaust pipe.


Risk from 3rd generation of AHSS

Long awaited the 3rd generation of AHSS, known also under popular name NanoSteel, named by the company with the same name that made breakthrough in its development, has entered the market in 2017. It has microstructure on the scale of nanometres - smaller compared to the existing steels.

Nano Steel provides the high strength required by automotive engineers (over 1000 MPa) in combination with significant ductility (up to 50 % elongation) – “the strongest available steels with the formability of mild steel”. This can provide what NanoSteel has identified as something every single OEM is looking for – geometric freedom, or the ability to create ultra complex shapes from sheet. A material from which complex shapes cannot easily be made, such as body parts, is limited in its application. Even the newest grades of steel now in use have to make large sacrifices in formability in order to deliver strength for automotive part design.

In short, the higher a material’s formability, the more an OEM can optimise a part’s geometry, and thus the thinner the sheet needed.

The new grades combine excellent strength and formability and could lead to weight savings of between 10 and 20 % in vehicle parts, compared to existing dual phase (DP) grades, according to ArcelorMittal.

However, despite obvious advantages of the 3rd generation of AHSS, when it is about weight saving and formability, it can compete successfully with the previous generations of AHSS but not with aluminium, in most of cases. Especially when it is applied at bigger vehicles. Aluminium will still be at 10-15 % in advance in lightweighting in most shapes and designs. Moreover, it is still in research & development phase while latest aluminium alloys are already in use.

Conclusions

The speed of aluminium adoption in automobiles and demand will vary among countries due to economic development and global differences in CO2 regulations. It is most important for aluminium use in future a good reputation of its use in existing models, before all Ford F 150 as the best selling vehicle in USA, but and other brands, as aluminium intensive Jaguar Land Rover models. So far, results are excellent - every model of aluminium car and truck crash tested has earned a 5-star safety rating. Consumers are satisfied, not just in terms of fuel economy, but in overall performance, durability and safety.

AHSS can not successfully compete with aluminium alloys in automotive industry for weight reduction purposes, especially in bigger vehicles (SUV’s, trucks etc).For the case 3rd Gen AHSS slows penetration of aluminium use in automobiles in future (aluminium sheet before all) auto producers will use the latest types of Al Alloys (series 5xxxx and 6xxx) with improved properties or even the highest grade aluminium alloys used in aerospace industry (series 7000-s) who can compete in properties (specific tensile strength and ductility) with AHSS. It would be more convenient for auto producers, despite higher costs, than to return to steel from aluminium.

Finally, with excellent safety grades of aluminium intensive cars, it is irrelevant than whether steel industry would offer steels with even higher tensile strengths from existing AHSS-s.

Light trucks and SUVs will contain the highest aluminium content. Larger and more expensive vehicles, and electric vehicles, will have higher than average content of aluminium, while smaller, lower-end vehicles will more rely on AHSS.

The fact that AHSS can not compete with aluminium in lightweighting vehicle is not a guarantee by itself that it will completely lose the battle to aluminium, especially in lighter vehicles.

The conclusion is in a long term projection of materials used in motor vehicles (by 2030 and beyond), the future cars will use a multi-material mix, combining steel, aluminium, carbon fibre, magnesium, plastics,mild steel, iron and other materials to achieve the weight, cost and performance targets, with no material dominance as it was the case with mild steel in the past.

The content of aluminium and steel (AHSS,3rd Gen AHSS & UHSS) will be dominant, each between 20 - 30 % content per a vehicle in average, while the remaining smaller percentage will include composite materials, magnesium, plastics and other, with each material fitting best for its purpose and characteristics. Finally, aluminium will be dominant material in big vehicles (SUV-s, trucks, pick-up-s), while AHSS will maintain dominance in smaller cars.

SPEECHES OF THE AUTHORGoran Djukanovic will be speaking at "33rd International Aluminium Conference" in Berlin and "ALUMINIUM 2018" in Düsseldorf. Both speeches will focus on aluminium in electric vehicles.

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