Printable aluminum alloy sets strength records

As a postdoctoral researcher, Mohadeseh Taheri-Mousavi was part of a class where students were challenged to design a printable aluminum alloy that would be stronger than any created to date. The class used computer simulations to outline a variety of combinations and to predict the resulting alloys’ strength. While the class was unable to produce a stronger alloy than current formulations, Taheri-Mousavi’s interest was piqued as a result of this exercise. She had an idea to combine these simulations with machine learning to efficiently explore the design space and since then she has continued to improve and apply these hybrid techniques to design higher performance alloys. 

Now an assistant professor of materials science and engineering at Carnegie Mellon University, Taheri-Mousavi has carried on work with collaborators from her postdoctoral experience at Massachusetts Institute of Technology (MIT), and they have developed a new formula for a printable aluminum alloy that is five times stronger than its conventionally manufactured counterpart. In a recently published study in Advanced Materials, she used her hybrid framework to efficiently explore the design space and design an aluminum alloy with enhanced strength and thermal stability.

“Machine learning tools can point you to where you need to focus, and tell you for example, which elements are controlling the formation of a microstructural feature,” said Taheri-Mousavi. “It lets you explore the design space more efficiently.”

Although the enhancement was not discovered after trying one million simulations without utilizing machine learning techniques, through her new approach, Taheri-Mousavi was able to identify a unique composition for the high strength printable aluminum alloy with thermal stability after evaluating only 40 possible combinations. Using this method, she was able to quickly narrow down to a formula for an aluminum alloy with higher volume fraction of extremely small (nanometer scale) precipitates, and therefore higher strength, than what previous studies have been able to identify. 

The prediction showed that only manufacturing methods with rapid solidification can realize this alloy in practice, so rather than using traditional metal casting to produce the new alloy, they used laser bed powder fusion (LBPF), a technique that creates complex parts by depositing powder layer by layer in a desired pattern before the layers are fused together by a high-power laser beam. The inherently rapid cooling and solidification that occurs in this process enabled the extremely small-precipitates, imparting high-strength in the alloy.

If we can use a lighter, high-strength material, this would save a considerable amount of energy for the transportation industry.

Mohadeseh Taheri-Mousavi, Assistant Professor, Materials Science and Engineering

“Because 3D printing can produce complex geometries, save material, and enable unique designs, we see this printable alloy as something that could also be used in advanced vacuum pumps, high-end automobiles, and cooling devices for data centers,” noted John Hart, professor and head of the Department of Mechanical Engineering at MIT, who also contributed to this research.  

After sending the powder, a mix of aluminum and five other elements, to collaborators at Paderborn University in Germany who printed small samples of the alloy, researchers at MIT ran tests to measure the alloy’s strength and analyze the samples’ microstructure. The results confirmed their predictions that the alloy was five times stronger than a casted counterpart and 50 percent stronger than alloys designed using conventional simulations without machine learning. 

“Usually alloys are redesigned to achieve properties of cast alloys, but here the rapid solidification during 3D printing makes alloys stronger, which is exciting.” Taheri-Mousavi says.

The new printable aluminum alloy has potential to be made into stronger, more lightweight and temperature-resistant products, such as fan blades in jet engines, which are typically cast from titanium, which is heavier and more expensive than aluminum.

“If we can use a lighter, high-strength material, this would save a considerable amount of energy for the transportation industry,” says Mohadeseh Taheri-Mousavi. “My dream is that one day, passengers looking out their airplane window will see fan blades of engines made from our aluminum alloys” 

The researchers are applying the hybrid framework to further enhance the alloy and optimize its other properties.