Study of crystallization phases and magnetic properties of Fe72.5Cr1Nb3Cu1Si13.5B9 nanocrystalline alloy prepared by rapid quenching method

Abstract

Phase constitution and soft magnetic properties of nanocrystalline alloy of composition Fe 72.5 Cr 1 Nb 3 Cu 1 Si 13.5 B 9 prepared by single roller rapid quenching technique was investigated in this paper. The amorphous nature and the nanocrystal formation of the alloy was determined by X-ray diffraction (XRD) besides the crystallization kinetics was studied by Differential Thermal Analysis (DTA). The annealing temperature was maintained within the range 450 o C to 800 o C for 30minutes. DTA study reveals the existence of two exothermic peaks one for primary crystallization of á Fe(Si) −phase and other for secondary crystallization of Fe 2 B phase. The temperature difference between two crystallization peaks is found to exist ~170 o C. This large temperature gap is an indication of the enhancement of stability of á Fe(Si − phase against detrimental Fe 2 B phase. In the optimized annealing condition, the grain size has been obtained in the range of 10-15 nm. The saturation magnetization (M s ) has been observed 128 Am 2 /kg. In as-prepared condition Curie temperature (T c ) was found 316 o C, close compared to the T c of original FINEMET. Thus, a slight substitution (1 atomic %) of iron (Fe) by chromium (Cr) in original FINEMET enhances the thermo-magnetic stability of the alloy.