Forming Ability, Thermal Expansion and Electrical Resistance Minimum of Fe-Metal Binary Amorphous Alloys

A systematic study of the forming ability of Fe-metal sputtered binary amorphous alloys has been carried out. Some magnetic properties, thermal expansion, and electrical resistivity of sputtered and melt-quenched amorphous alloys have been investigated. The lower limit of forming ability depens not only on the size difference but also on the valence difference between Fe and the solute element. Where the valence difference is smaller than 3, the forming ability is predominantly restricted by the size difference. By increasing the valence difference, the effect of size difference becomes less important, and the lower limit of Fe-IIIB alloy systems hardly depends on the size difference. The lower limit is also changed by the cooling temperature of the substrate. For example, the limit is lowered by several percent when the substrate is cooled by liquid nitrogen. The thermal expansion curves exhibit a remarkable anomaly due to the Invar effect which is common in Fe-based amorphous alloys. Peculiarly, the dilute alloys containing about 10% of the solute element show a remarkable shrinkage even above the Curie temperature. The electrical resistivity minimum occurs not at the Curie temperature but above it, which is closely correlated with a magnetic behavior. Fe-Y amorphous alloys having spin glass behavior also show a similar thermal expansion anomaly and electrical resistivity minimum. It is believed that the inhomogeneous magnetic state in Fe-metal amorphous alloys is responsible for the peculiar behavior mentioned above.