A metallic element modified by the addition of one or more other elements or by the addition of nanotech devices.
Dumb Alloy: A metal that has been hardened or otherwise modified by the addition of other metals or nonmetallic impurities (carbon is a popular nonmetallic element but others can be used as well). Because the added atoms are the wrong size for the metal lattice, they tend to position themselves at flaws and weak points, where they pin the defects in place.
Smart Alloy: instead of raw atoms, simple reactive nano-devices are used. These are able to respond to and interact with the metal as conditions allow, thus producing a far harder alloy.