“Competition among materials will always spawn innovations”
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Arconic emerged from the Alcoa Group in 2016 and is now one of the key development service providers and manufacturers in the light metal field. In an interview, Achim Hofmann and Felix Sellmann explain the importance of additive manufacturing, why lightweight design pays off in commercial vehicles and what aerospace material is about to make the leap to automotive engineering.
lightweight.design: The introduction of the Audi spaceframe in 1994 was a great moment for aluminium. In reaction to this the steel industry developed steels with very high strengths. Composite materials are now increasingly coming onto the market. Will aluminium fall behind in the lightweight material mix of the future?
Hofmann: A few years ago, genuine competition did actually emerge, which we in the aluminum industry also encouraged — not least through the Audi project. This ongoing competition among materials is set to continue and set beyond doubt to keep spawning innovations again and again. Moreover, we welcome the challenge of developing ever more innovative products. I feel pretty confident that our aluminum materials will play an important role. However, what is equally important is to further develop the other materials handled by our group — titanium, nickel, steel and also new processes such as additive production — as well as continuing to develop joining technologies and embracing new competition as a result. Ultimately, we advocate using the best material in the right place.
Aluminum-lithium alloy has attracted a great deal of attention in aircraft design for some years now. Was the competition among materials also one of the triggers for developing this alloy?
Hofmann: Technically speaking, we should be speaking of aluminum-copper-lithium, but the term aluminum-lithium has established itself. And yes, just a few years ago, we also found ourselves competing with composite materials in aviation. That spurred us on to develop new aluminum materials. Even though aluminum-lithium has been used by our customers for several years now: aluminum-lithium alloys enabled us to breathe new life into aluminum as a material and to put it center stage again. The first large-scale use of aluminum-lithium was in the Airbus A380, and since then it has been used in the construction of almost all modern aircrafts. Here we have managed to meet our customers’ requirements — namely lightweight design and increased performance — while not ignoring the need to keep costs down.
“We had already given up on solving these issues with titanium materials.”
What is the stand-out feature of aluminum-lithium?
Hofmann: We have achieved very low density, higher stiffness, extremely high-strength mechanical properties and excellent corrosion resistance. Doing so has opened up applications which we previously thought beyond the reach of titanium materials. Ultimately, combining these material properties is what was key to making ultra-efficient lightweight design possible. And it’s worth mentioning that the so-called third generation of aluminum-lithium materials has emerged since they were first used in the A380. Over the years lessons have been learned and we have been able to significantly optimize the material properties compared to first and second generations. In addition, aluminum-lithium alloys enable us to produce complex multi-chamber hollow profiles. These are used, for example, in automotive engineering. Although this would normally be out of the question with conventional high-strength aluminum materials, aluminum-lithium has already proved itself in this field. In other words, the design freedom offered by high-strength profiles is greater than it’s ever been.
That said and outstanding properties notwithstanding, it is also a comparatively expensive material.
Hofmann: Naturally, we can’t ignore the question of cost. By investing in what is likely the largest and most technically advanced aluminum-lithium foundry anywhere — in Lafayette, Indiana (USA) — we have gone a long way towards reducing the manufacturing costs of these special alloys. We are thus well-placed, both qualitatively and quantitatively, to meet the requirements of our customers, from aviation as well as other fields, such as automotive engineering. However, what we need to address is not only pure production costs, but also those of the entire product life cycle. So the question is: How can I reduce costs by increasing performance through the use of these materials — over the entire life cycle? As well as the need to save weight, other aspects must also always be taken into account: Is the material reliable? Sustainable? How can it be processed and joined? And what would the alternative be?
Against a background of increasingly varied materials used in aircraft design, what significance will developing new joining technologies have in the coming years?
Hofmann: Very considerable. It makes no sense at all if we develop a great material with excellent properties and are then unable to join it to others. We already include this important aspect in the material development so that we can tailor the material properties for the application at hand. Even within a material group, challenges arise, for example when joining different aluminum alloys. However, the challenge becomes even greater if you find yourself wanting to go beyond your own material group and join different types of material.
Are you also working on new joining technologies at Arconic?
Hofmann: Yes, absolutely. We are one of the world’s largest manufacturers of high-strength connecting elements for the aerospace industry, but we are also active in the automotive and transportation sectors. We work intensively, not only on pure mechanical connections, but also welded and soldered connections for example. We do not see ourselves as a pure material manufacturer, but more as a solution provider. We do not simply launch a material onto the market — instead, we work with our customers to develop a solution and ultimately get the best possible result from our material development. Ultimately, it is academic whether aluminum, titanium or any other alloy is used in the finished product.
What new joining technologies will we need in the years to come?
Hofmann: Mechanical connections will continue to hold sway, as well as welding and soldering. And new manufacturing processes such as additive manufacturing present us with a whole host of fresh new possibilities and challenges. At the moment everyone is talking about additive manufacturing — which is also one of our top priorities. This is evidenced by what we’ve developed in the field of powder development and production. Joining technology is also of interest in this context. How do we bond a material produced by 3-D printing? How can I combine this new printing technology with existing production processes? On the material and process side, additive manufacturing offers us new opportunities and challenges.
In the additive manufacturing field, you cooperate with Airbus.
Hofmann: Yes, I see this Joint Development Agreement as clear evidence of our customers’ interest in working on such issues. 3-D-printed components have great potential in aviation as well as numerous other applications.
What innovations will this cooperation spawn?
Hofmann: For example, we are working on the so-called Ampliforge process. Here, we combine additive manufacturing processes with the classic forging process. This allows us to exploit the advantages of both processes; resulting in components with improved material properties and reduced material input. Unfortunately, however, I am not yet able to comment on other possible applications that we are developing together with Airbus. What I can say is that leveraging additive production opens up whole new opportunities: at Arconic, we are capable of covering a wide range of different materials. As well as aluminum, we also focus on titanium materials, nickel alloys and titanium aluminides — all of which can be combined with 3-D printing processes. We are well-placed as a technological leader in the additive production field, thanks also to our experience in the field of powder production: What we bring to the table is over a century of experience in producing aluminum powders.
“In the field of commercial vehicles, demand for lighter design methods is clearly emerging.”
42 % of sales in 2017 were generated in the aerospace sector. Other key Arconic business fields are automotive, commercial and rail vehicles, which collectively comprise 25 % of sales. Mr. Sellmann, is the soaring electromobility trend already making its presence felt in your business?
Sellmann: We predict that many market participants may want to use lightweight design techniques to compensate for the additional weight of batteries. What this does is spur people to produce applications — battery housings and other lightweight structural elements — that help improve vehicle range or driving dynamics. This is already an area in which we forecast an upswing in demand for aluminum as well as other light metals. However, we don’t want to differentiate electric and conventional vehicles to any great extent: the challenges and opportunities are basically the same.
You have been selling forged aluminum wheels for 70 years under the Alcoa-Wheels name. This means that you have been active in the lightweight design of commercial vehicles for decades, so to speak.
Sellmann: Yes, this is a strong market that continues to grow — not least in the field of electric city buses, which are in demand among various European cities. We are in close contact with urban bus companies. And we have seen a clear tendency emerge in the past few years: Hybrid or all-electric drives are no longer just being experimented with — they are now being implemented. This brings with it higher weight. Demand for lighter designs is clearly emerging. Here, our forged aluminum wheel represents a particularly efficient component — all you need to do is remove the wheel used previously and fit ours. Our product also lets you achieve up to 47 % weight savings compared to steel wheels. Which is also something that can’t be ignored.
How do you assess the willingness of fleet operators to spend more on lightweight design?
Sellmann: Citing the example of our wheels business, I can reaffirm soaring demand in recent years, which was behind our announcement in March that we are expanding our factory in Hungary. One example: In a country like Germany, a vehicle combination with more than four axles may normally transport up to 40 t, including vehicle weight and loading. If a wheel is up to 47 % lighter than a steel wheel, with an average specification on five axles, you can save up to 212 kg using our Alcoa wheels. In turn, the weight saved allows higher loads and so optimized operation ensures the investment swiftly pays for itself.
You mentioned your close network of urban bus companies. Public authorities are increasingly turning to environmentally friendly options and lighter vehicles, and aluminum represents one solution here. However, primary aluminum is extremely energy-intensive to produce. Will this end up hindering the wider use of aluminum?
Sellmann: I can’t really answer that because we do not produce aluminum — or at least no longer produce it. What we actually do at Arconic is to work with our partners to analyze entire product life cycles, from the manufacturing of primary aluminum, to the usage phase and finally recycling. As you know, aluminum can be recycled very efficiently. It allows a closed material cycle, and this gives it an advantage over many other materials.
So what share of an Alcoa rim is actually recycled?
Sellmann: Let’s get the basics straight first. Aluminum can be repeatedly recycled, as evidenced by the fact that 75 % of the aluminum produced to date remains in circulation. Studies show that more than 90 % of aluminum from passenger cars and over 95 % of aluminum from trucks and trailers — including their wheels — is recycled after the vehicles are taken out of service. Where our wheels are concerned, there are differences depending on the design and production location, but as far as European wheels are concerned, we can say around 90 % are made from recycled material.
Hofmann: Recycling is a key point and its scope goes beyond Alcoa wheels. All our metallic products have an advantage here. Let’s take aluminum as an example: the costs of primary aluminum are naturally higher. Even so, we can reduce these costs through our recycling process. For example, we reuse process scrap generated in our plants or at our customers in further processing, or we recycle products that are taken back from the market. The value of the previously discussed aluminum-lithium alloys lies not only in the aluminum content, but also in lithium and copper as alloy components and the high purity of the alloys. So the focus is not just on materials, but also on recyclable materials. While recyclability undeniably gives aluminum a major advantage, it also has to make sense in terms of overall costs.
“It is only a matter of time before these materials are also used in passenger cars and trucks.”
1 kg saved can cost considerably more in aircraft design than in automotive engineering. Are you still able to develop materials with equal appeal for both industries?
Hofmann: Yes, as evidenced again by the example of aluminum-lithium materials. We originally developed these for structural aviation applications. Nowadays they can also be found in the Pure Power engines made by Pratt and Whitney. Incidentally, they are the first ever forged aluminum fan blades. Aluminum-lithium alloys are now making inroads into passenger cars and trucks. These materials already have a presence in the racing field. Although I can’t disclose more at this point, it is only a matter of time before these materials will see service in the car and truck sector for special applications in the near future. In particular, where weight is not the only issue, but also to increase the performance of vehicles powered by internal combustion engines. Our task will involve discussing these relatively new materials and their properties more in greater detail with our customers’ development departments. And by this I mean the scope beyond aviation in particular. In addition to automotive engineering, we also see potential for motorcycles, high-end bicycles and in the energy sector.
So the intention is to use aluminum-lithium in powertrain components?
Hofmann: Correct. Aluminum-lithium has excellent temperature resistance compared to conventional aluminum materials. The material can be used where high rigidity and strength, good fatigue behavior and low density are required. And where high temperatures are the norm. For example, applications in the drive area can be considered, such as turbochargers or even brakes, where they have been used in racing for several years.
Dr. Hofmann, Mr. Sellmann, thank you very much for the interview.
Interview: Thomas Siebel