Grain size effect on magnetic properties of Fe–28Cr–15Co permanent magnets as a function of Mo content

Abstract

The Fe–28Cr–15Co–(1–4)Mo magnetic alloys were studied using X-ray diffraction, optical microscopy, transmission electron microscopy and magnetometery techniques. Permanent magnets were produced by employing thermo-magnetic aging process. The Fe–28Cr–15Co–3.5Mo alloys produced the optimum magnetic properties as coercive force = 840 Oe (66.83 kA/m), remanence = 11 kG (1.1 T), saturation magnetization = 12.5 kG (1.25 T) and energy product = 5.4 MGOe (43 kJ/m3). Molybdenum content above 3.5 wt% produced cracking and brittleness in the alloys due to the formation of unwanted σ phase. The results indicates that molybdenum content from 1 to 3.5 wt% extends the ferromagnetic α grain structure at annealed state and affects the particle size, amount and shape anisotropy of the strongly magnetic α1 phase that in turn improves the magnetic properties of the ternary Fe–28Cr–15Co alloys. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)