Multiprobe analyses on nucleation and evolution of nanocrystallization process in a high saturation magnetization soft magnetic Fe–Si–B–P–Cu–C alloy

Abstract

This study aimed to explore the impact of annealing temperature on the nucleation and subsequent growth of nanocrystalline α-Fe grains in a high saturation magnetization soft magnetic Fe_84.8Si_0.5B_9.4P_3.5Cu_0.8C_1.0 alloy. Thus, we conducted multiprobe analyses of the isothermal crystallization process within 633–733 K. Transmission electron microscopy and atom probe tomography observations of the samples isothermally annealed at 733 and 633 K revealed distinct differences in their microstructures. In case of the higher isothermal temperature, larger Cu clusters were observed, whereas the α-Fe grains were finer. In contrast, in case of the lower isothermal temperature, the Cu clusters were smaller, and the α-Fe grains were coarser. Time-resolved synchrotron radiation X-ray diffraction measurements confirmed the sporadic nucleation mechanism, highlighting the significant effect of isothermal temperature on the formation of α-Fe grains. To achieve an optimal microstructure for lower coercivity, the Cu clustering and α-Fe nanocrystallization must be controlled by annealing at higher temperatures for shorter durations.

Graphical Abstract