NIST discovers that novel crystal form boosts strength of 3D-printed metal

09 Apr 2025

Quasicrystals formed in an icosahedron shape reinforce laser-printed aluminum airplane parts.

Andrew Iams, a materials research engineer at the U.S. National Institute of Standards and Technology (NIST), saw something strange while looking through his electron microscope. He was examining a sliver of a new aluminum alloy at the atomic scale, searching for the key to its strength, when he noticed that the atoms were arranged in an unusual pattern. “That’s when I started to get excited,” said Iams, “because I thought I might be looking at a quasicrystal.”

Not only did he find quasicrystals in the aluminum alloy, but he and his NIST colleagues found that these quasicrystals also make it stronger. They published their findings in the Journal of Alloys and Compounds.

The alloy formed under the extreme conditions of laser-metal 3D printing. NIST says that understanding this aluminum on the atomic scale “will enable a whole new category of 3D-printed parts such as airplane components, heat exchangers and car chassis”. It will also open the door to research on new aluminum alloys that use quasicrystals for strength.

Quasicrystals are like ordinary crystals but with a few key differences. A traditional crystal is any solid made of atoms or molecules in repeating patterns. There are only 230 possible ways for atoms to form repeating crystal patterns. Quasicrystals do not fit into any of them; their unique shape lets them form a pattern that fills the space, but never repeats.

3D printing creates shapes that would be impossible with any other method. For example, in 2015 GE designed complex but lightweight fuel nozzles for airplane engines that could only be made with metal 3D printing. In contrast, the previous version had to be assembled from 20 separate pieces and was 25% heavier. One of the limitations of current metal 3D printing is that it only works with a handful of metals. “High-strength aluminum alloys are almost impossible to print,” said NIST physicist Fan Zhang, a co-author on the paper. “They tend to develop cracks, which make them unusable.”

Why so hard to 3D-print aluminum?

Regular aluminum melts at around 700 degrees C. The lasers in a 3D printer must raise the temperature much higher: above the metal’s boiling point of 2,470 degrees C. This changes a lot of the properties of the metal.

In 2017, a team at HRL Laboratories, based in California, and UC Santa Barbara discovered a high-strength aluminum alloy that could be 3D printed. They found that adding zirconium to the aluminum powder prevented the 3D-printed parts from cracking, resulting in a strong alloy.

The NIST researchers set out to understand this new, commercially available 3D-printed aluminum-zirconium alloy on the atomic scale. “In order to trust this new metal to function in critical components such as military aircraft parts, we need a deep understanding of how the atoms fit together,” said Zhang.

The NIST team wanted to know what made this metal so strong. Part of the answer, it turned out, was quasicrystals. When Iams viewed the crystals from the right angle, he saw that they had fivefold rotational symmetry.

“Fivefold symmetry is very rare. That was the telltale sign that we might have a quasicrystal,” said Iams. To confirm the team had identified a quasicrystal, Iams had to carefully rotate the crystal under the microscope and show that it also had threefold symmetry and twofold symmetry from two different angles.

“Now that we have this finding, I think it will open up a new approach to alloy design,” said Zhang. “We have shown that quasicrystals can make aluminum stronger. Now people might try to create them intentionally in future alloys.”