Influence of Ge on crystallization kinetics, microstructure and high-temperature magnetic properties of Si-rich nanocrystalline FeAlSiBCuNbGe alloy

The influences of Ge addition on crystallization kinetics, microstructure and high-temperature magnetic property of nanocrystalline FeAlSiBCuNbGe alloy have been investigated. The results showed that doping a small amount of Ge into Fe72.7Al0.8Si17.5B5Cu1Nb3 alloy can lower the activation energy and therefore decrease the glass forming ability. The primary crystalline temperature Tx1 and secondary crystallization temperature Tx2 were slightly decreased. But the addition of Ge enhances the Curie temperature of amorphous phase, which significantly improved high-temperature magnetic softness. Average grain sizes were increased and thickness of intergranular amorphous layer was decreased due to the addition of Ge to alloys. The optimum annealing temperature for Fe72.7Al0.8Si17.5B5Cu1Nb2.6Ge0.4 alloy was obtained at 843 K. The reason for the enhancement in high-temperature magnetic softness was systematically analyzed in terms of the evolution of microstructure.