Amorphous Steel

Amorphous steel with large cross-sections, long a goal of metallurgists, has been fabricated by scientists at Oak Ridge National Lab. The amorphous steel produced has a hardness and strength more than twice that of the best ultra-high-strength conventional steel. Some amorphous (glassy) iron-based alloys have been employed in making transformer cores, the electrical devices which transform electricity from one voltage to another, and have reduced energy losses thereby by two-thirds. But not until now has glassy steel of the kind used in building structures been made.

Steel, an alloy of mostly iron atoms with varying amounts of carbon and other elements, is ordinarily a crystal, with an internal structure consisting of neat rows of atoms. If produced quickly from a liquid phase, however, a disordered solid can result. The trick is to find conditions---including the chemical content of the alloy, such as the addition of yttrium in this case---that favor the liquid phase and frustrate the onset of crystallization even as the solidification temperature is approached.

The researchers (Zhou Ping Lu, 865-576-7196, luzp@ornl.gov) have produced centimeter-sized pieces of the amorphous steel, and they feel that structural steel in bulk metallic glass form can be produced economically with traditional drop-casting methods, in which metallic glasses are made by pouring the hot liquid into a cold copper mold. (Lu et al., Physical Review Letters, 18 June 2004.

See mention of related work reported by a University of Virginia group (Ponnarnbalam et al., J. Mat. Res, 5 May 2004) and by a Caltech group (Xu et al., Physical Review Letters, 18 June 2004).