Influence of applied tensile stress on magnetic properties of surface-crystallized Fe-based amorphous ribbons

Fe-based amorphous alloys containing Al or Ti as impurities become surface-crystallized during casting, with a resultant increase in their soft magnetic properties. This phenomenon is known to be caused by compressive stress induced by surface crystallization, but there have been few systematic investigations of this compressive stress. In the present study, the compressive stress was found to range from 1 to 15 MPa, and is proportional to the ratio of the surface crystalline layer thickness to the ribbon thickness. The relationship between the compressive stress and core losses has been examined. This result shows that the increase of the core losses is mainly caused by the compressive stress induced by the surface crystalline layer.