The peculiarities of the nanocrystallization process and copper addition effects for an amorphous Fe 75.5Si 13.5B 9Cu 2 alloy

Abstract

The crystallization process and copper addition effects of an amorphous Fe 75.5Si 13.5B 9Cu 2 alloy were investigated by DSC, DIL, XRD and TEM. The experimental results show that copper addition decreases the activation energy of primary crystallization as well as the structure relaxation temperature, and thus causes Fe–Si–B metallic glasses less stable. During annealing process of Fe 75.5Si 13.5B 9Cu 2 alloy, it is found that metastable Fe 3B phase precipitates which is confirmed by both XRD results directly and thermal expansion coefficient curves at the heating rates of higher than 10 K/min indirectly. Moreover, equiaxed nanometer-sized grains of Fe–Si are promoted without forming coarse dentritic morphology due to copper addition of 2 at.%. By annealing isothermally at 773 K for 60 min, homogeneous Fe–Si nanograins (about 25 nm) with more than 65% volume fraction are obtained in favor of good soft magnetic properties.