Creep or tensile stress induced anisotropy in FINEMET-type ribbons?

Abstract

Continuous stress annealing can be performed on FINEMET-type (Fe 73.5 Cu 1 Nb 3 Si 15.5 B 7 ) ribbons. Here we report experiments conducted in a cheap open tubular furnace as a function of pulling velocity ( v ). We achieved up to v =120 m/min that is almost 100 times higher than previously reported for this kind of equipments. In this report we show for the first time how the properties are depending on the pulling velocity. While the achieved relative permeability µ r remained constant without changing any other parameter than v , the elongation of the ribbon and the contraction of the ribbon width were monotonically changing as v was increased. The results support that the creep is not determined exclusively by the applied stress, but it is determined by the details of the amorphous–nanocrystalline transformation, which is influenced by the pulling velocity. The bigger the pulling velocity is, the higher the onset temperature of the amorphous–nanocrystalline transformation is, and the wider the associated exothermic peak is, resulting in increased elongation of the ribbon due to a short time formation of undercooled liquid state. • We report detailed investigations as a function of pulling velocity in a dynamical stress annealing process. • The inverse effective permeability is linearly depending on the applied stress, in accordance with Herzer’s back-stress theory. • The creep is not uniquely determined by the stress, but depends also on the pulling velocity. • The permeability is independent from the elongation of the ribbon. • The induced anisotropy does not depend on the creep.