MIT researchers recently pulled on a piece of cracked metal so hard that they expected it to break apart. Instead, something unexpected happened: The crack healed.
“We had to go back and check,” MIT materials science and engineering professor Michael Demkowicz said in a release. “Instead of extending, [the crack] was closing up. First, we figured out that, indeed, nothing was wrong. The next question was: ‘Why is this happening?’”
It turns out that under very precise conditions, certain types of metal, including the nickel used in this case, can heal on their own. Many metals are composed of tiny grains that repeat in regular patterns. If a crack forms in part of a grain, but not all the way across it, applying the right type of tension causes the grain to heal itself.
Researchers think that by studying the strange property, they can learn how to incorporate it into metals used in products like airplanes. Large metal structures can build up tiny cracks over their lifetime, eventually becoming unsafe. A material that heals tiny cracks as they form, and well before they become a more serious issue, would have the potential to last longer.
“That’s a field we’re just opening up,” Demkowicz said in the release. “How do you design a microstructure to self-heal? This is very new. If you can figure out how to prevent those nanocracks, or heal them once they form, or prevent them from propagating, this would be the kind of thing you would use to improve the lifetime or safety of a component.”