Structure and magnetic properties of amorphous and nanocrystalline Fe85.4Hf1.4B13.2 alloy

Abstract

Purpose: The forming of magnetic properties of the nanocrystalline Fe-based are different than those in conventional ferromagnetic materials that is: the soft magnetic properties increase with decreasing of grain size of crystalline phase Design/methodology/approach: The nanocrystalline Fe-based alloys could be obtain by many different methods, in this work first amorphous ribbons were obtained by planar-flow casting method and after that amorphous precursor were heat treated. The changes of structure associated to crystallization was investigated by X-ray diffractometry, the analysis of Mössbauer spectra made it possible to determine the average hyperfine field and volume fractions of α Fe crystalline phase. The changes of coercive force (Hc) of tapes were investigated using coerciometer with the terrestrial magnetic field compensation. Findings: The obtained results of investigations shows that crystallization process of amorphous Fe85.4Hf1.4B13.2 allowed to form nanocrystalline structure. This crystallization process has two-stages character and exhibit redistribution of the phases stages. The changes of magnetic properties has been observed with increasing the temperature annealing of investigated alloy. The coercive force is decreasing and minimum Hc is obtained at temperature 523 K. The obtained results showed clearly that for examined alloy is possible to determine the specific thermal treatment conditions (Top) causing an improvement of the magnetic properties. Practical implications: The possibility of optimization of soft magnetic properties is obtaining by the use of controlled crystallization of amorphous alloys. Originality/value: It has been found that the Fe85.4Hf1.4B13.2 alloys consisting of a mostly single bcc structure with nanoscale grains exhibit much better soft magnetic properties than in example well-known nanocrystalline Fe73.5Cu1Nb3Si13.5B9 . The group of Fe – M – B alloys is called NANOPERMTM. From a viewpoint of industrial application they are very attractive materials especially because of the highest BS among the nanocrystalline alloys