METALLIC GLASSES :

A metallic glasses is a solid resulting from non-crystallization during cooling from liquid state. The properties of the metallic glasses are a combination of both metals and alloys. 

Preparation:

    The metallic glasses are prepared by several methods employing special techniques, which involve rapid solidification of the melt. Melt spinning is one such technique used to prepare metallic glasses.

The molten alloy flow through the outlet of the quartz tube and it is cooled at a ultrafast rate with the help of a rotating cooled copper cylinder. On impact with the rotating drum, the melt is frozen with in a few milliseconds producing a long ribbon of metallic glasses.

Properties:

1.    Metallic glasses are non-crystalline, they are ferromagnetic. The lack of long range ordering results zero bulk magnetic crystal anisotropy on an average. Due to that, they posses low magnetic losses, high permeability and saturation magnetization with low coercivity. Thus they resemble the very soft magnetic alloys.

2.    Metallic glasses posses high strength and tensile strength, it is around 3.6 GPa. Thus, metallic glasses are superior than common steels. This is based on their structure since the random ordering does not have any lattice defects like dislocation and grain boundaries.

3.    Metallic glasses have higher workability. Thus they can be cold worked upto half their thickness without cracking.

4.    Metallic glasses have high electrical resistance with nearly zero temperature coefficient of resistance. Only at very low temperature there is a sharp variation in resistance.

5.    Metallic glasses are not affected by irradiation, high corrosion resistance.

Applications:

1.    Metallic glasses are suitable for applications in electronic circuits because of their insensitivity to temperature variation.

2.    They are widely used as resistance elements in electric circuits due to their high electrical resistivity.

3.    Metallic glasses posses high Vicker’s hardness and corrosion resistance, they have found applications as materials for magnetic tape recording heads.

4.    The use of metallic glasses in motors can reduce core loss by as much as 90% as compared with conventional crystalline magnets.

5.    Possible applications of metallic glasses include sensitive and quick response magnetic sensors or transducers. Security systems and power transformer cores.

Metallic glasses as transformer core material:   

    The ferromagnetic properties of metallic glasses have received a great deal of attention, probably because of the possibility that these materials can be used as transformer cores. Because some metallic glasses have excellent magnetic properties, there is a great incentive for developing advanced techniques for producing large sheets of these materials to be used as transformer cores.

    These large sheets of metallic glasses are widely used in power distribution transformers which convert high voltage electricity in power lines to 240 V for domestic use. Power transformers made of metallic glass are smaller in size and efficient in their performance as compared to the conventional transformers which are very large in size.