SHAPE MEMORY ALLOYS

Once upon a time, in a far-off land, there were spectacles you could crumple up in your hand when you weren't using them. There were metal statues which rose up with the sun and bits of metal which lifted mountains... This is no alchemist's misty dream or surrealist writer's fantasy however. It's the world today. A new class of alloys, used in space technology and for making women's underwear, looks like revolutionising all our knowledge and use of metals.

Shape Memory Alloys (SMA) look just like other metals — rigid, strong and a yellow or silver colour. But they have an extraordinary characteristic. A "heat memory" which enables them to change shape with the temperature. SMAs can usually be bent when cool, but acquire a pre-programmed fixed shape as they get hotter. So you can open a key-ring as easily as if it was plasticine if you put it in the freezer for a few seconds. A quick blast from a hair-dryer would be enough to make car bumpers bounce back into shape after an accident.