The influence of Cu addition on the crystallization and magnetic properties of FeCoNbB alloys

Abstract

The influence of Cu addition on the crystallization process, the nanocrystalline microstructure and the magnetic properties has been studied in the Fe 78−x Co x Nb 6 B 16−y Cu y (x = 18, 39, 60; y = 0, 1) alloy series. Cu addition clearly refines the nanocrystalline microstructure for the alloys with the lowest Co content, but the effect is reduced as the Co content increases. Refinement of the microstructure stabilizes the nanocrystalline microstructure by shifting the second crystallization process to higher temperatures. Cu addition mainly affects the magnetic properties for the lowest Co containing alloys. A fitting procedure of coercivity versus crystalline volume fraction is performed for these alloys in the frame of the random anisotropy model extended to twophase systems and assuming constant magnetoelastic anisotropy.

Correlation between microstructure and temperature dependence of magnetic properties in Fe60Co18(Nb,Zr)6B15Cu1 alloy series

“…% Cu addition in Hitperm alloys containing Nb with 18 at. % Co. 13 If no Cu is added to this alloy, nanocrystallization shows the formation of very irregular nanocrystals ͑ϳ25 nm in size͒ whose shape can be interpreted as agglomerates of smaller and more regular units ͑ϳ5 nm in size͒. This microstructure is very similar to that found in Hitperm alloys containing Zr with Fe/ Co= 0.5, where Cu clustering phenomenon is absent.…”

Crystallization kinetics and soft magnetic properties in metalloid-free (Fe, Co)90Zr10 amorphous and nanocrystalline alloys

“…Crystal size, D, is almost independent of Tann but partial substitution of Co for Fe yields a reduction of D from ~30 nm to ~20 nm, whereas similar crystalline volume fractions, XC, are obtained for equivalent Tann (equal difference between Tann and peak temperature). This indicates that nucleation is enhanced and grain growth is more constrained in the Co containing alloy with respect to the Co-free one, in agreement with the observed reduction in crystal size after partial Co substitution for Fe in B-containing NC alloys [11,12]. This is ascribed to the non-preferential partitioning of Co into the crystalline phase [13,14], which implies a higher relative Fe enrichment of the crystallites in Co containing samples with respect to Cofree ones, limiting their growth due to a fast depletion in Fe of the vicinity of a growing bcc Fe(Co) crystal [15].…”

Detection of the onset of nanocrystallization by calorimetric and magnetic measurements

“…6 Consequently, the mean grain sizes are very different: D ϳ 5 nm for Cu-HT and ϳ20 nm for HT. 7 In the case of the FM alloy, the Cu-clustering phenomenon is also present, and the mean grain size of the ␣-Fe, Si phase at the end of nanocrystallization is ϳ15 nm. 2 Although the Cu-clustering phenomenon occurs in both the FM and Cu-HT alloys, a larger grain size is obtained in the case of FM.…”