COOLING IT

In any case, metallic glasses cannot yet be produced in any shape or size, for it is not easy to achieve a cooling rate of a million degrees per second. Among the research labs now competing for leadership, the front runner seems to be Allied Chemical, whose researchers inject hot, liquid metal between two counter-rotating drums that are continuously cooled. This produces thread-like ribbons of metallic glass at stupendous rates - more than a mile a minute!

It is these fibers that combine high strength with plasticity, exceeding metals and glasses in both aspects. They are cheap to produce, because apart from their high production rate, they are produced in a form obviating the need for expensive and energy-consuming processes such as casting, rolling and drawing.

One cannot make gas turbines or other automobile engines from these new miracle materials, but an obvious application of the strong, plastic, cheap fibers is reinforcement filaments for automobile tires. The only limitation is that their recrystallization temperature must never be exceeded in the manufacturing process, or they would turn back to brittle metals.

The reason why glassy metals can, as yet, be produced only as thin, thread-like ribbons is that a ribbon has a large surface-to-volume ratio, enabling the heat to be dissipated extremely rapidly. If the hot metal were cast into a form, no matter how cold, the heat in the inner bulk of the volume could not be carried away quickly enough to prevent recrystallization, and the metal would become brittle as in ordinary quenching.