Amorphous metal alloys

The very first synthetic metallic amorphous glasses were reported in the literature by Kramer, in the 1930s, during his studies on the electrical properties of metallic thin films. Au-Si glasses were obtained by vacuum evaporation and condensation of the alloy on a surface cooled by liquid nitrogen.

The amorphous state of matter, in the general sense, had long been known, since it is the structural state of common silica glasses produced by natural cooling of molten oxide mixtures. However, this was the first time that the amorphous state had been obtained by cooling essentially metallic compounds. The properties of these new materials were rapidly identified, and their originality initiated a great deal of fundamental and applied research (see § 1 ).

Because of the particularly attractive properties of certain alloys, production methods have been developed on a pilot scale and then on an industrial scale. These include melt-spinning for concrete reinforcement and permanent magnet alloys, and planar flow for soft magnetic alloys, competing materials with oriented Fe Si, Fe Ni and ferrites. These machines are highly productive, with ribbons running at speeds of up to 20 m/s, and ensure direct strip shaping from the liquid state.

Solid metallic glasses are innovative for their mechanical properties (high strength, up to 4GPa, reasonable toughness from 10 to $100\text{Mpa}\sqrt{m}$ ), but still require improvements in terms of behavior (in particular, the lack of ductility remains prohibitive) and formability, to find applications.

A series of techniques for producing amorphous alloys is described in § 2.4 .