Partitioning of Co during crystallisation of Fe–Co–Nb–B(–Cu) amorphous alloys

Partitioning behaviour of alloying elements during the primary crystallisation of both Fe18Co60Nb6B16 and Fe39Co39Nb6B15Cu1 alloys has been studied using three-dimensional atom probe (3DAP). Cu rich clusters were found in the Cu-containing alloy, and they provided nucleation sites for the primary α-Fe(Co) particles. In the Cu clusters, concentration of both Fe and Co was greatly decreased. In both Cu-containing and Cu-free alloys Nb and B were depleted in the α-Fe(Co) particles and enriched in the remaining amorphous phase. However, Co concentration in the α-Fe(Co) was the same as the remaining amorphous phase. Based on the 3DAP analysis, the phase volume fraction has been estimated.