Shape Memory Alloy
Date: Around 1993
What is a shape memory alloy and how does it work?
These are materials that can be deformed somewhat, (for example,
folded, bent, twisted, etc,) and then when they are heated up a little, they
return to almost their original shape. I believe that the principle is that
there are impurities, called dislocations, that are locations where atoms are
out of place. Some of these are extended through out large regions of the
material. When you bend the material these are deformed but not destroyed.
When you heat the material up these dislocations tend to move to their
original shape and carry the surrounding material with them. This restores
the shape. If the material is melted or heated to much the dislocations are
changed or completely destroyed and this property is gone.
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Update: June 2012