Influence of the addition of Mn and Cu on the nanocrystallization process of HITPERM Fe–Co–Nb–B alloys

Devitrification of Fe39−xMnxCo39Nb6B16−yCuy (x=0, 2, 4; y=0, 1) alloys takes place in two main stages: primary crystallization gives rise to ultrafine α-FeCo crystals embedded in an amorphous matrix and a recrystallization process occurs in the second stage to give a (FeCo)23B6-type phase as the main product. Cu alloying decreases the crystallization onset and affects the kinetics of nanocrystallization and the resulting microstructure. Mn addition decreases the Curie temperature of the amorphous phase but only slightly increases its thermal stability. The exclusion of Mn atoms from the α-FeCo crystals is suggested.