J. Wang/NIST
Andrew Iams 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 extremely unusual pattern. "That's when I started to get excited," said Iams, a materials research engineer, "because I thought I might be looking at a quasicrystal."
Not only did he find quasicrystals in this aluminum alloy, but he and his colleagues at the National Institute of Standards and Technology (NIST) 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 metal 3D printing, a new way to make metal parts. 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.
What Are Quasicrystals?
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. Table salt is a common crystal, for example. Salt's atoms connect to make cubes, and those microscopic cubes connect to form bigger cubes that are large enough to see with the naked eye.
There are only 230 possible ways for atoms to form repeating crystal patterns. Quasicrystals don't fit into any of them. Their unique shape lets them form a pattern that fills the space, but never repeats.
Dan Shechtman, a materials scientist at Technion-Israel Institute of Technology, discovered quasicrystals while on sabbatical at NIST in the 1980s. Many scientists at the time thought his research was flawed because the new crystal shapes he found weren't possible under the normal rules for crystals. But through careful research, Shechtman proved beyond a doubt that this new type of crystal existed, revolutionizing the science of crystallography and winning the chemistry Nobel Prize in 2011.
Working in the same building as Shechtman decades later, Andrew Iams found his own quasicrystals in 3D-printed aluminum.
How Does Metal 3D Printing Work?
There are a few different ways to 3D-print metals, but the most common is called "powder bed fusion." It works like this: Metal powder is spread evenly in a thin layer. Then a powerful laser moves over the powder, melting it together. After the first layer is finished, a new layer of powder is spread on top and the process repeats. One layer at a time, the laser melts the powder into a solid shape.
">
