Discovery to inspire more radiation-resistant metals

By Brooks Hays  |  Dec. 16, 2016 at 12:09 PM
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ANN ARBOR, Mich., Dec. 16 (UPI) -- Metals exposed to radiation at high temperatures swell. That's a problem for the nuclear energy and aerospace industries.

Scientists at the University of Michigan may have found a solution. Researchers there found metal alloys boasting three or more equally distributed elements are resistant to radiation-induced swelling.

Radiation undermines metallic structures. When a radiation particle collides with metal, atoms are knocked from the material's crystal structures. The displaced atom is reabsorbed elsewhere. The phenomenon encourages swelling, as well as the formation of cavities. Expelled atoms leave behind empty spaces that can coalesce and create structural vulnerabilities.

Until now, materials scientists have worked to build in microstructures that organize cavities in way that limits their ability to undermine the metal's structural integrity.

Researchers at Michigan and Oak Ridge National Laboratory decided to take a different approach to the problem and began testing metal alloys with less corruptible crystalline structures. Experiments showed crystals formed of equal parts nickel, cobalt and iron were more resilient to radiation particles. Crystals formed of equal parts nickel, cobalt, iron, chromium and manganese were also resistant to radiation.

"These materials have many good properties such as strength and ductility, and now we can add radiation tolerance," Chenyang Lu, a postdoctoral research fellow in nuclear engineering and radiological sciences at Michigan, explained in a news release.

In radiation exposure tests, pure nickel suffered 100 times more radiation damage than the preferred alloys.

Further analysis showed the alloys unique and more varied microstructures worked to contain displaced atoms. Because the atoms don't travel far and the crystals are more intimately arranged, the material is better able to repair itself. Displaced atoms are more likely to find their way back into crystal structures.

"In simplified terms, if there are a lot of atoms of different sizes, you can consider them bumps or potholes," said Lumin Wang, a professor of nuclear engineering and radiological sciences at Michigan. "So this defect won't travel so smoothly. It will bounce around and slow down."

The new research was published in the journal Nature Communications.

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