Feature originally published in the September/October 2023 edition of 3D ADEPT Mag. Interviews, roles and projects remain in that historical context.
Metal Additive Manufacturing applications are filled with examples that involve the use of titanium, Inconel and recently, pure copper. As we are exploring the next phase of growth of this segment, we need to consider aluminum and aluminum alloys as the range of materials AM users can capitalize on. The only thing is that the benefits one can get by processing aluminum alloys with AM are underrated, even overlooked and the weird part of it, is that I understand why.
Aluminum and its alloys have long served aerospace, automotive and packaging applications. Depending on the grade, their properties include low weight, mechanical strength, malleability, electrical conductivity and corrosion resistance; recyclability is another advantage. Casting, sheet forming and machining remain important conventional manufacturing routes.
“There are excellent options for making high-performance aluminum parts. For example, aluminum alloys can be machined much more readily than other metals (titanium, stainless steels…). We can cast aluminum into complex shapes, we can form sheets into beverage cans or automotive body panels. Many assembling processes exist (welding, brazing, mechanical assembly, adhesive bonding… And of course, aluminum is infinitely recyclable. This is why aluminum is the material of choice in many packaging and transportation applications, particularly when light weight and/or recycling are the drivers,” Alireza ARBAB, Head of Additive Manufacturing at Constellium told 3D ADEPT Media.
Costs need to be compared for a defined grade, feedstock form and process. Market conditions, material preparation, quantities and qualification requirements matter: aluminum is not invariably less expensive than every other metal mentioned here.
These favorable properties and these cost considerations have raised the interest of AM users and AM solutions providers that have started exploring how they could combine these advantages with the ones of AM, providing this way another manufacturing option to vertical industries adopting AM.
The article below aims to understand the opportunities and challenges of aluminum AM. To do so, it will highlight:
- First, aluminum or aluminum alloys?
- The different AM technologies that can process aluminum: key focus on LPBF and a manufacturing process specifically designed for aluminum components
- The AM applications that will drive the use of aluminum alloys across the metal AM segment
- And the considerations that one should take into account to explore a sustainability route.
Pure aluminum or aluminum alloys?
Why use alloys rather than pure aluminum? The answer depends on the application. Pure aluminum offers good conductivity, but its limited mechanical strength may be unsuitable for a structural part. Alloying and treatment allow properties to be tailored to the intended use.
The feature cited Elementum 3D and m4p (metals 4 printing) among suppliers exploring these materials, without establishing an exhaustive list. Elementum 3D’s A1000-AM data sheet describes pure aluminum powder. This differs from its reinforced aluminum-matrix composite A1000-RAM10; the two grades should not be conflated.
“Aluminum is almost always alloyed and heat-treated or work-hardened to increase strength. The alloy depends on the application. Casting and PBF both require melting and flow, as such they commonly have high levels of silicon and the resulting parts are prone to porosity. This reduces the strength of the parts. Alloy’s Sheet Forging process does not require melting or flow, and as a result a wider array of aluminum alloys is possible and porosity is not an issue. Our first alloy is 6061 – fully dense,” Alison Forsyth, CEO of Alloy Enterprises explains.
Moreover, it can be alloyed with many other elements to overcome its low strength. According to Arbab, aluminum can be combined with elements such as Magnesium, Zinc, Copper, Silicon, Manganese, to name a few. The key is to be able to design the right aluminium alloys for different markets and production processes.
Additive manufacturing technologies for aluminum
Powder bed fusion is an important route for aluminum. Directed energy deposition (DED), including wire-arc and electron-beam approaches, and binder jetting are other routes studied or offered according to the material and process. WAAM and EBAM are therefore not separate families from DED. Compatibility needs to be checked for each grade and system.
Compared to other metals, the high reflectivity towards the typical fibre laser wavelength, the high thermal conductivity and tendency to crack during solidification are items that make it difficult to process aluminum with a laser beam process. That’s why conventional casting alloys such as AlSi10Mg and AlSi12 have been mainly used for LPBF. They are relatively easy to process compared to high-strength Al alloys.
Among the aforementioned processes, Laser Beam Powder Bed Fusion (LPBF) and Directed Energy Deposition (DED) can use a laser beam – the latter of which can use powder or wire as a feedstock.
Laser powder bed fusion
Constellium’s Head of AM told 3D ADEPT Media that “the many alloys developed for existing applications are not optimized for production using AM technologies, in particular Laser Powder Bed Fusion (LPBF).” For the expert, a look at the big picture is necessary to understand the full process – from powder management to the final parts, including printing, post-processing and quality control – and the areas that may require specific points of interest.
“Our Aheadd® CP1 alloy [a material specifically designed for AM] uses the advantage of the extremely rapid solidification rate of LPBF allowing Constellium to use specific alloy design rules to create a much better solution. As an example, CP1 contains 1% of iron as a key alloying element. In most aluminum alloys, iron alloy is limited as impurity”, he points out.
On another note, in addition to high reflectivity and low laser absorption that may result in defects, the properties of certain aluminum alloys may also result in defects like porosity, cracks, poor surface finish, shrinkage, oxidation and residual stress.
Furthermore, each 3D printer comes with a set of unique parameters. This means that an issue observed in machine X may not necessarily be the same as the issue observed in machine Y.
A 2020 study by Leirmo and Baturynska groups potential defect-reduction approaches into composition changes, laser-power adjustment, scan strategy and powder predrying. Their suitability depends on the alloy and equipment; they are not universal settings.
Alloy Enterprises’ Sheet Forging process
Alison Forsyth opened our eyes to a new way to fabricate aluminum parts and materials using high-speed manufacturing. For Forsyth, aluminum is different from other metals because it “forms a robust oxide layer in milliseconds. This makes it difficult to bond or print, particularly in processes with a high surface area-to-volume ratio which maximizes the amount of oxide. Alloy’s Sheet Forging process has been designed to overcome this challenge.”
Speaking of their Sheet Forging process, she explained that “Alloy Enterprises is transforming how aluminum components are made. Alloy manufactures fully dense aluminum components, enabling customers to scale from prototype to production. Unlike powder-based additive manufacturing processes, Alloy’s Sheet Forging process is high-throughput and produces components with superior material properties. The process starts with digitally slicing the 3D component into discrete layers. The layers are then laser-cut from Alloy’s custom feedstock and an inhibiting agent is selectively applied to create in-situ supports. The full stack of registered sheets is then diffusion-bonded together. Finally, the parts are removed from the block and heat-treated. Alloy’s process provides the flexibility of wrought material properties and the geometric complexity of additive manufacturing to produce lightweight components with optimal strength, durability, and thermal conductivity.”
The preceding description sets out advantages claimed by Alloy Enterprises. This feature provides no independent throughput comparison with LPBF, so a general speed advantage cannot be inferred.
Applications for aluminum alloys
Among the vertical industries mentioned above, one industry that may see the increasing use of aluminum alloys is the EV industry. The more EVs will be developed, the more OEMs in this sector will need strong, lightweight materials such as aluminum.
According to Alloy Enterprises’s CEO, aluminum will be part of the electrification journey of everything that moves, and flexible on-demand cost-competitive fabrication will be essential to this transition. Speaking of their Sheet Forging process especially, she explains: “Automotive, EV, heavy and industrial equipment can all be served by Alloy’s Sheet Forging process. Additionally, some aluminum alloys have high thermal conductivity relative to its weight. Cooling and thermal management applications, as we pack more batteries or electronics into vehicles, machines, and computers, will continue to drive adoption of Alloy’s Sheet Forging process.”
For Arbab, there are already many exciting LPBF applications that can be achieved with aluminum alloys. They include, for instance, satellite components, defense, heat-exchangers, and high-end automotive parts.
“As costs come down and designers become more aware of the new possibilities brought by specific alloys such as Aheadd® CP1. We already receive many requests for application studies in areas such as on-demand spare parts, semi-conductor industry applications…The current business is just the tip of the iceberg,” he adds.
Sustainability: feedstock, reuse and the full life cycle
The interviews also considered environmental impacts arising from feedstock production, alongside powder reuse.
Forsyth stated that the Sheet Forging feedstock was designed to reduce carbon emissions by a factor of 15 compared with powder. This is a supplier claim about feedstock, without a detailed comparative assessment provided here; it is not the full life-cycle footprint of a part. She also stated that scrap could be reused while avoiding some recycling operations. The conditions and energy requirements of reuse still belong in an environmental comparison.
Reusing powder in a machine is different from recycling metal by remelting. Material condition and part properties must be controlled; unlimited reuse cannot be assumed. At the time of the interview, Arbab described Constellium’s work on powder-production yield, quality and recycling with a pilot atomization line at IRT M2P in northern France.
That being said, understanding the full lifecycle of a material is probably the first step to take for companies that are looking to produce more sustainable products and this should be the main topic of another article.
This feature was first published in the September/October 2023 edition of 3D ADEPT Mag. Featured image: Alloy Enterprises.
Review note: publication context, technical terminology and comparison limits clarified; supplier results remain attributed.
THE 3D ADEPT WEEKLY NEWSLETTER
The industry moves fast. Stay ahead.
Every week, the latest additive manufacturing news, in-depth features and real-world applications, straight to your inbox. Plus, be the first to know when a new issue of 3D ADEPT Mag is out.
Free · One email a week · Unsubscribe anytime
Clicking loads our email provider’s sign-up form, including its analytics and Google’s anti-bot protection. You’re only subscribed if you complete the sign-up. Read our privacy policy.