Scientists find that metals have a natural ability to heal themselves

The development could see self-healing engines, bridges, and airplanes reverse damage caused by wear and tear.
Loukia Papadopoulos
Studying metal cracks at the nanoscale.jpg
Studying metal cracks at the nanoscale.

Craig Fritz, Sandia National Laboratories 

For the first time ever, researchers have observed metals that successfully heal themselves without any human intervention. The development could see self-healing engines, bridges, and airplanes reverse damage caused by wear and tear, making them safer and longer-lasting.

This is according to a press release from Sandia National Laboratories and Texas A&M University published Wednesday.

“This was absolutely stunning to watch first-hand,” said Sandia materials scientist Brad Boyce.

“What we have confirmed is that metals have their own intrinsic, natural ability to heal themselves, at least in the case of fatigue damage at the nanoscale,” Boyce said.

“From solder joints in our electronic devices to our vehicle’s engines to the bridges that we drive over, these structures often fail unpredictably due to cyclic loading that leads to crack initiation and eventual fracture,” Boyce said.

“When they do fail, we have to contend with replacement costs, lost time and, in some cases, even injuries or loss of life. The economic impact of these failures is measured in hundreds of billions of dollars every year for the U.S.”

Up to now, the notion of a self-healing metal has largely remained elusive.

“Cracks in metals were only ever expected to get bigger, not smaller. Even some of the basic equations we use to describe crack growth preclude the possibility of such healing processes,” Boyce said.

The proven theory

The new discovery began in 2013 when Michael Demkowicz — then an assistant professor at the Massachusetts Institute of Technology’s Department of materials science and engineering, now a full professor at Texas A&M — published a new theory that under certain conditions metal should be able to weld shut cracks formed by wear and tear.

The discovery that his theory was true was quite a surprise.

“We certainly weren’t looking for it,” Boyce said.

Khalid Hattar, now an associate professor at the University of Tennessee, Knoxville, and Chris Barr, who now works for the Department of Energy’s Office of Nuclear Energy, were only trying to evaluate how cracks formed and spread when, surprisingly, about 40 minutes into the experiment, the damage reversed course. One end of the crack fused back together seamlessly. 

Hattar called it an “unprecedented insight.”

The researchers shared the development with Demkowicz, who recreated the experiment on a computer model, substantiating that the phenomenon witnessed at Sandia was the same one he had theorized years earlier.

However, research on the self-healing metal process remains in its infancy. 

“The extent to which these findings are generalizable will likely become a subject of extensive research,” Boyce said. “We show this happening in nanocrystalline metals in vacuum. But we don’t know if this can also be induced in conventional metals in air.”

“My hope is that this finding will encourage materials researchers to consider that, under the right circumstances, materials can do things we never expected,” Demkowicz said in the statement.

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