An amorphous metal is a solid metallic alloy material that exhibits an unusual atomic-scale structure compared to all other metals.
Most metals are crystalline in their solid state. Their atoms are arranged in a highly-ordered state. Amorphous metals, on the other hand, have a disordered arrangement of atoms and are non-crystalline with a glass-like structure.
The first successful production of an amorphous metal (also known as metallic glass) occurred at Caltech in 1960. This unique glass-forming alloy was cooled extremely rapidly to avoid crystallization. The first applications of the alloy were limited to wire, foil and metal ribbons because thicker materials couldn’t be cooled rapidly enough to achieve the desired non-non-crystalline structure
By the 1990s, new amorphous alloys were being developed at a much lower cooling rate by using methods of simple casting into metallic molds. This procedure opened the door to a wide variety of industrial uses for amorphous metals.
How are Amorphous Metals produced?
Amorphous metals are produced by several differing procedures, all of which are complex and require specialized equipment and trained personnel.
Early experimenters at Cal Tech learned they could produce an ultra-thin ribbon of amorphous metal by splattering molten metal onto a spinning ultra-cold disk. The motion caused the alloy to cool too fast to form a crystalline structure. The result was a metal that was locked into a glassy state.
Today, the solid-state reaction route is the most widely used method for the preparation of amorphous metals commercially followed by ion irradiation and mechanical alloying methods.
Uses of Amorphous Metal
Amorphous metals are technically glasses, but they are much tougher and less brittle than regular oxide glasses and ceramics. And unlike common regular glass, which is used for electrical insulators on power lines, amorphous metals display a high degree of electrical conductivity
The important commercial application of amorphous metals is mainly due to its special magnetic properties and high electrical conductive nature. The low-magnetization loss is also useful in high-efficiency transformers.
Two commercial products, Liquidmetal and Vitreloy, use amorphous metal alloys to manufacture various items like watches and cell phone covers. The alloys they use combine a number of desirable features like high tensile strength and excellent resistance to harmful corrosion that surpass regular metals.
Another positive quality is its high coefficient of restitution (COR). This measure of the “restitution” of a collision between two objects and how much kinetic energy remains for the objects to rebound makes the material ideal in the manufacturing of thin-faced golf club heads.
The ability to cast and mold amorphous Liquidmetals plus its high resistance to wear has resulted in it replacing plastic materials in some instances. Apple is testing the viability of using amorphous metals to see if they are able to retain a scratch-free surface longer than competing materials made in complex shapes.
Heavy industry also uses various amorphous metals as protective coatings for industrial machinery, on petroleum drill pipes and for boiler tubes in electrical plants.
In some cases, the metals can replace titanium in certain applications for medical instruments, military vehicles and the aerospace industry. Amorphous metal rods are also being used to replace depleted uranium rods in kinetic energy devices.
In one of the first applications in space, Liquidmetal plastics were used on the Genesis space probe as solar wind ion collectors.