Metallic glasses

A piece of ordinary glass is a silicate material that did not crystallize when cooled from its liquid state to ambient temperature. Other substances, especially those whose molecules tend to polymerize, can also be cooled to ambient temperatures without crystallization. With metals, however, this could not be done until rather recently, and doing it continuously to make materials of interest to engineering is a very recent development. Metal alloys that can be quenched without crystallization form metallic glasses—solids with unusual, and in some cases outstanding, physical properties. Because their atoms are bound together by long-range metallic bonding, these glasses are malleable and good electrical conductors (comparable to stainless steels), unlike covalently bonded silicate glasses.