Effect of heat treatment on dynamic magnetic properties and microstructures of Fe73.5Cu1Nb3Si13.5B9 nanocrystalline alloy

In this work, as-quenched Fe73.5Cu1Nb3Si13.5B9 amorphous strips were treated by conventional one-step and two-step annealing processes, respectively. And the magnetic properties (core loss and dynamic coercivity), crystallization kinetics and microstructures of annealed samples were investigated. Results show that two-step annealing process can effectively improve magnetic properties and optimize microstructures. More uniform grain size distribution was achieved by two-step annealing process compared with one-step annealing process, owing to promoting nanocrystallite nucleation and inhibiting further grain growth by two-step annealing process. And some nanocrystallites tend to be adjacent to grain boundary rather than be surrounded by remaining amorphous in all surfaces of nanocrystallines. Nevertheless, too much low-angle grain boundaries in nanocrystalline ribbons would lead to deteriorate magnetic properties. What interesting is that the relation, between dynamic coercivity and external field, associated with nanocrystallization temperature, could be a practical method to characterize the change mechanism of magnetization, and needs to be confirmed by further theoretical and experimental investigation.