In the 1991 film “Terminator 2: Judgment Day,” a malevolent time-traveling, shape-shifting robot called the T-1000, made of liquid metal, exhibits a unique quality. If hit by explosions or bullets, your metal will heal on its own.
A self-healing mineral is still just science fiction, right? Apparently no.
Scientists on Wednesday described how pieces of platinum and pure copper spontaneously heal metal stress cracks during nanoscale experiments designed to study how these cracks form and propagate in metal under stress. They expressed optimism that this ability could be turned into minerals to create self-healing machines and structures in the relatively near future.
Metal stress occurs when metal – including parts in machinery, vehicles and structures – sustains microscopic cracks after exposure to stress or repetitive motion, damage that tends to worsen over time. Metal fatigue can cause catastrophic failures in areas that include aviation – jet engines, for example – and infrastructure – bridges and other structures.
In experiments conducted at the US government’s Sandia National Laboratories in New Mexico, researchers used a technique of screwing the ends of small pieces of metal together about 200 times per second. The crack formed and initially spread. But about 40 minutes into the experiment, the metal melted again.
The researchers called this cure “cold soldering.”
“Cold welding is a metallurgical process that occurs when two relatively smooth, clean surfaces of a metal are brought together to fix atomic bonds,” said Brad Boyce, a materials scientist at Sandia National Laboratories who helped lead the study published in the journal Nature. .
Boyce added: “Unlike the self-healing robots in ‘Terminator’, this process is not visible at the human level. It happens at the nanoscale and we have yet to control this process.”
The metal pieces were 40 nanometers thick and a few micrometers wide. While curing has only been observed in experiments on platinum and copper, Boyce said the simulation indicated that self-healing can occur in other metals and that it is “quite plausible” that alloys such as steel exhibit this quality.
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