For the first time, scientists have discovered that metal heals itself after cracking – an observation that could pave the way for creating structures and robots capable of repairing themselves.
But for those who worry about the upswing Terminator robots are realistic Don’t: The newly discovered mechanism only works on a handful of minerals and on incredibly small scales — at least, for now.
“Of course, there are plenty of industries in which product engineers would like to translate these findings into intentional engineering approaches to create automatically self-healing metals in our structural applications,” said the lead author. Brad BoyceA materials scientist at Sandia National Laboratories in Albuquerque, New Mexico, told Live Science. “Self-healing metals can be useful in a wide range of applications from aircraft wings to automobile suspension systems.”
Related: The real-life “Terminator 2” robot can melt to escape from prison, then harden on command
Scientists had previously assumed that metals were unable to repair themselves, but a new discovery, made inadvertently by scientists studying nanometer-sized pieces of platinum and copper, overturns that conclusion.
Metals are damaged by stress or repetitive motion, creating growing networks of microscopic cracks that can lead to catastrophic failures of jet engines, bridges and other vital structures.
But not all materials break under repeated stress: some modern polymers even Ancient Roman concrete Has been shown to repair microcracks over time.
In 2013, a team of researchers used computer models to show that minerals might also be able to perform the healing trick, but they weren’t able to study minerals at the exact scales necessary so they couldn’t get any real evidence.
In the new study, published July 19 in the journal natureUsing a device called a transmission electron microscope, the scientists investigated how the nano-sized pieces of metal respond to repeated stress. The device applied very little force — the equivalent of stepping on a mosquito’s leg — in the form of 200 tiny metal tugs every second.
in two metals, copper And PlatinumCracks appeared and grew all over the material. But after 40 minutes, the metals fused together again, leaving no trace of cracks.
According to Boyce, the explanation for this miraculous self-repair lies in a process called “cold welding”.
“In short, at the nanoscale, the local conditions around the tip of the crack cause the two sides of the crack to push against each other,” Boyce said. “Upon contact, the two sides fuse together in a process metallurgists refer to as ‘cold welding.’ This process does not seem to happen all the time, but only in cases where local conditions result in wing contact.”
The feasibility of the researchers’ new observations remains unknown. First, to observe cold welding processes, the scientists isolated the metals inside a vacuum so that there was no atmosphere atoms interfered with the equipment. This means that they do not yet know whether or not the process only works in a vacuum.
Similarly, the range of potential metals that can self-repair is also unknown. Scientists have only observed cold welding in platinum and copper, but whether commonly used structural metals such as steel also perform this feat is not yet clear.
There is also the issue of sizing. The minerals used were small and highly ordered in their structures; It is also not known if macrominerals can be coaxed into healing.
However, the scientists are cautiously optimistic that their discovery could lead to fundamental changes in the way we build and engineer metal structures for durability, and could have applications in spaceflight, where atmospheric particles are not a problem.
“In fact, we think this process may already occur to some extent even in ordinary metals and alloys that we use in our daily lives — at least for subsurface cracks that are not exposed to oxygen, and perhaps even for surface cracks,” Boyce said. “To get the most out of it, though, we can start thinking in sections of materials and designing microstructures.”
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