Metallic Glass

A metallic glass, also known as an amorphous metal or glassy metal, is a metallic material that lacks a crystalline structure. Bulk metals typically have a highly-ordered crystalline structure, whereas a metallic glass is amorphous in nature, much like a glass. Various methods are used to fix the metal's structure in an amorphous state, and the result is a material which possesses a number of novel properties with promising future applications.

How it's made

All metallic glasses are produced by cooling a metal alloy quickly enough so that crystals do not have time to form. Just how this is achieved has evolved since these materials were first discovered.

Rapid cooling

The first metallic glass was produced in 1960 by W. Klement (Jr.), Willens and Duwez at Caltech. It was a 75/25 gold/silicon alloy that was solidified by cooling it from the liquid state at an extremely high rate of roughly one million Kelvin per second. This rapid cooling process forced the material into an amorphous state by not allowing the metal atoms enough time to order themselves into a crystal lattice. An unfortunate limitation of this process was that metallic glasses could only be formed as extremely thin samples, as heat needed to be removed quickly in order to frustrate crystallization of the material. This rapid cooling technique remained the only viable method for producing metallic glasses for nearly three decades, and with the limitations of the method, few applications could be realized.

Although the method didn't much change, the necessary rate of cooling did see a dramatic decrease over the years. In 1969, a 77.5/16.5/6 palladium/silicon/copper alloy was developed that could be cooled at a much slower rate on the order of several hundred Kelvin per second. Various other alloy formulations allowed continued progress toward still lower minimum cooling rates.

Shear and fatigue

http://www.sciencedaily.com/releases/2009/03/090324091211.htm http://blogs.physicstoday.org/update/2009/03/confining-cracks-in-metallic-g.html http://www.msnbc.msn.com/id/29738048/

References

http://en.wikipedia.org/wiki/Amorphous_metal