Abstract:
Magnetic materials play a fundamental role in designing electrical and electronic machines, equipments and devices and basically it is the material and secondly the design, which controls the performance and efficiency of a device. Therefore, magnetic material development, which is closely associated with the technology being followed for its manufacturing shall lead to an improvement in the performance of electrical/electronic equipments/devices.
Iron-phosphorous alloys are soft magnetic materials and magnetic properties and toughness both improve with increase of phosphorous content for these alloys as for as phosphorous remains in solid solution form in a-iron, which is about 1.2%.Phosphorous alloying addition improves the resistivity of the iron and decreases the coercivity effectively and thus decreases hysteresis loss of the alloy. It also improves alloys formability. But it is necessary that entire phosphorous remains in solid solution with iron. This is not possible in wrought metallurgy owing to its sensitivity to segregation during solidification. Introduction of phosphorous in iron is therefore only possible with Powder Metallurgical processing.
Phosphorous is an undesirable impurity in wrought steels. It is responsible for cold and hot shortness in wrought steels. This is due to Phosphorous segregation along grain boundaries. In melting and casting route the last liquid to solidify is rich in Phosphorous. However, in conventional powder metallurgy phosphorous iron is to admixed high purity atomized iron powder with ferrophosphorous.Pherrophosphorous powder normally has some degree of carbon, nitrogen, and oxygen besides other contaminants. The presence of these elements is deleterious to structure sensitive magnetic properties.
