Study on nanocrystalline grain size and quantitative change in Fe–Cu–Mo–Si–B soft magnetic alloy

Abstract

In this paper, we studied the grain size and volume fraction change of [Formula: see text]-Fe(Si) nanocrystalline phase as a function of Cu, Mo and Si content in Fe[Formula: see text]Cu[Formula: see text]Mo3Si[Formula: see text]B9, Fe[Formula: see text]Cu1Mo[Formula: see text]Si[Formula: see text]B9, Fe[Formula: see text]Cu1Mo3Si[Formula: see text]B[Formula: see text], and also the annealing temperature and time in Fe[Formula: see text]Cu1Mo3Si[Formula: see text]B9 alloy. Cu is an element promoting ultrafine structure and crystallization progresses, it causes the grain size of the [Formula: see text]-Fe(Si) phase to decrease suddenly, the volume fraction of [Formula: see text]-Fe(Si) phase to increase only by adding 0.5 at.% Cu. Also, Mo causes the grain size of [Formula: see text]-Fe(Si) phase to decrease like Cu, while suppressing the increase of the volume fraction of [Formula: see text]-Fe(Si) phase, Si has no little effect on the grain size of [Formula: see text]-Fe(Si) phase, diffuses into the inner part of [Formula: see text]-Fe(Si) phase upto Si 13.5 at.%, but suddenly increases grain size above Si 13.5 at.%. The microstructure of Fe[Formula: see text]Cu1Mo3Si[Formula: see text]B9 alloy is nearly completed at 520[Formula: see text]C for about 20 min, the grain size is approximately 13.8–14.1 nm, the volume fraction of [Formula: see text]-Fe(Si) phase is within 61–66%, initial permeability at 1 kHz is within 59,800–61,100.