By Mark Waghorn
Metals can heal themselves – just like Arnold Schwarzenegger’s cyborg assassin in “The Terminator“, according to new research.
It opens the door to self-fixing engines, bridges, airplanes, and even rockets – for manned missions to Mars.
In experiments, stunned scientists saw microscopic cracks vanish – offering hope of machines that mend on the spot.
Lead author Dr. Brad Boyce, of Sandia National Laboratories in Albuquerque, New Mexico, said: “This was absolutely stunning to watch first-hand.
“What we have confirmed is metals have their own intrinsic, natural ability to heal themselves – at least in the case of fatigue damage at the nanoscale.”
This is one-way machines wear out and eventually break — Repeated stress or motion causes tiny cracks to form.
Over time, they grow and spread until – snap! The whole device breaks.
It is a particular worry in spacecraft design. A round trip to the Red Planet will take at least 21 months.
The fissure the US team saw disappear was a minute but consequential fracture – measured in nanometers.
“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,” said Dr. Boyce.
“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 US,” continued Boyce.
Self-healing materials have mostly involved plastics – until now. The notion of a self-healing metal has largely been the domain of science fiction.
“Cracks in metals were only ever expected to get bigger – not smaller,” said Dr. Boyce; “Even some of the basic equations we use to describe crack growth preclude the possibility of such healing processes.”
The serendipitous discovery is based upon a decade-old theory that under certain conditions metal should be able to weld shut cracks formed by wear and tear.
“We certainly weren’t looking for it,” said Dr. Boyce.
The researchers meant to evaluate how cracks formed and spread through a nanoscale piece of platinum using a specialized electron microscope technique.
Surprisingly, about 40 minutes in, the damage reversed course. One end of the crack fused back together as if it was retracing its steps, leaving no trace of the former injury. Over time, the crack regrew along a different direction.
A lot remains unknown about the process, including whether it will become a practical tool in a manufacturing setting.
“The extent to which these findings are generalizable will likely become a subject of extensive research,” said Dr. Boyce.
“We show this happening in nanocrystalline metals in a vacuum, but we don’t know if this can also be induced in conventional metals in air,” he continued.
The study in Nature has been described as a “leap forward” at the frontier of materials science.
Co-author Professor Michael Demkowicz, of Texas A&M, who came up with the original idea, said: “It suggests under the right circumstances materials can do things we never expected.”
Produced in association with SWNS Talker
Edited by Judy Marie Sansom and Jason Reed