Preferential Co partitioning to α-Fe in nanocrystalline CoFeNbB alloys by Mn addition

Influence of Mn addition on the microstructure and hyperfine parameters of amorphous and nanocrystalline Co60(FeMn)18Nb6B16 alloys has been studied. Although Mn addition does not yield significant differences in crystallization kinetics and in the phases formed after each transformation, it seriously affects the partitioning of Co during nanocrystallization. Whereas for Mn free alloy Co is homogeneously distributed throughout the amorphous matrix and the nanocrystals, in Mn containing alloy Co is enriched in the α-FeCo nanocrystals. This fact prevents the exhaustion in Fe of the amorphous matrix and the crystalline volume fraction achieved at the end of nanocrystallization in the case of Mn containing alloy is ∼20% higher than in the Mn free alloy.