Here are 2 demos that I do when I am talking about structures of metals and alloys:

 

The Atomic Trampoline Kit available from ICE:  Guaranteed wow factor!

http://mrsec.wisc.edu/Edetc/background/amorphous/

Memory Metal: I have a stash of 2" long wires so that I can give one to each student.

http://mrsec.wisc.edu/Edetc/background/memmetal/