APPLICATIONS OF AMORPHOUS WIRE

In-water-quenched amorphous magnetic metal wire has been available for a decade. In this time, the unique properties of the wire have created many new uses, especially in the field of electronic devices and sensors. Because of the near-ideal mechanical properties of amorphous metal, the wire can be die drawn to various wire diameters which can be much smaller than is possible with polycrystalline magnetic materials. Diameters of any value from the as-cast value of about 135 mum down to 10 mum are available. Also the wire can be used in applications where mechanical strength as well as unique magnetic characteristics are needed. Since magnetic metals are typically magnetostrictive, changing the chemical composition of the amorphous wire can be used to change the magnetostriction which, in combination with residual or applied stress, provides yet another opportunity to tailor the magnetic character to the device needs. Flux reversal lies at the heart of all electronic devices since the ultimate output is always a voltage to interact with the other electronic elements. Wire can have a longitudinal flux change or a circumferential flux change or a combination of two. The most curious, although not necessarily the most useful, is the re-entrant longitudinal reversal found in magnetostrictive as-cast and die-drawn tension-annealed wire. Re-entrant reversal takes the same time and hence generates the same voltage, essentially independent of the drive field amplitude or frequency within the range of electromechanical devices. It is useful for tachometers where the frequency changes or security sensors where the drive field changes over a wide range. Since the reversal mechanism involves a magnetic domain wall propagating along the wire, distance sensors are also possible. By twisting the magnetostrictive wire, the longitudinal flux can be coupled to the circumferential flux which links the wire itself. This Matteucci effect allows the sensor to be driven or the output voltage observed between each end of the wire, providing a great convenience and flexibility for some types of devices. The ability to drive the reversal using a current through the wire is also popular with non-magnetostrictive wires. Here, the sharp and predictable demagnetizing effects resulting from the wire geometry make the wire attractive for electronic device applications such as the data tablet, miniature chokes and transformers.