A Moment of Science

Metal Memory

Are you familiar with shape memory alloy? There's no actual memory involved, at least not in computer or human terms.

paper_clips

Photo: Mykl Roventine

Say that a paperclip had shape memory properties. At its current, relatively cool temperature, you could bend it, right?

Are you familiar with shape memory alloy?

A shape memory alloy is a metal alloy, or something made of two or more different kinds of metal, that you can bend and distort but then return to its original shape by heating it to a certain temperature.

There’s no actual memory involved, at least not in computer or human terms. It all has to do with crystal structure. Say that a paperclip had shape memory properties. At its current, relatively cool temperature, you could bend it, right?

That’s because its crystal structure is such that it’s soft enough to bend, twist, or whatever. Heat a shape memory alloy above a certain point, though, and its crystal structure changes.

It becomes more rigid and in the process reverts to its original shape, meaning the shape it first assumed when created at the higher temperature.

So, what are shape memory alloys good for?

Well, a bunch of stuff. Like in treating coronary disease, for example. Doctors insert distorted shape memory stents into arteries. When the body’s heat warms the stent it expands to its original shape and opens up the artery to allow increased blood flow.

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