MIT has played home to a number of off-the-wall discoveries, and once more a recent discovery of the self-healing properties of metal has thrown the researchers there for a loop. Initially thought as a mistake, MIT researchers unexpectedly found out that putting a cracked piece of metal under tension — that is, exerting a force that would be expected to pull it apart — has the reverse effect, causing the crack to close and its edges to fuse together.
It happened due to grain boundaries interaction with cracks in the crystalline microstructure of a metal — in this case nickel, which is the basis for “superalloys” used in extreme environments, such as in deep-sea oil wells. The surprising finding could lead to self-healing materials that repair incipient damage before it has a chance to spread. The results were published in the journal Physical Review Letters in a paper by graduate student Guoqiang Xu and professor of materials science and engineering Michael Demkowicz.
Their experiment wasn’t just saying that metal can sometimes heal itself to some small extent. Instead, their findings suggested that there is a mechanism through which metal can actually heal its cracks under any applied stress, slow the progression of this type of failure, Demkowicz says. Such failures can be “life-limiting situations for a lot of materials,” Demkowicz says, including materials used in aircraft, oil wells, and other critical industrial applications. Metal fatigue, for example — which can result from an accumulation of nanoscale cracks over time — “is probably the most common failure mode” for structural metals in general, he says.
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Source: MIT, dvice.com, engineering.com
Camilla G.//SMC Editor
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