Evolution of the microstructure and magnetic properties of as-cast and melt spun Fe2NiAl alloy during aging

Fe2NiAl-based alloy with the nominal composition Fe51.1Ni23.5Al23.7Si1.7 was prepared by casting and melt-spinning. Comparison of the phase composition, microstructure and magnetic properties of water-quenched bulk samples and melt spun ribbons after isothermal aging in the 500-900 degrees C range were carried out TEM investigations of the decomposition of the solid solution into beta- and beta(2) phases during cooling or quenching and subsequent aging have revealed different types of decomposition products. The optimal periodic modulated structure with coercive force H-c similar to 700 Oe was observed after cooling of as cast alloy at a critical rate. In this structure the paramagnetic beta(2) phase forms a continuous network that isolates elongated single domain ferromagnetic beta particles. The water quenched bulk samples and melt spun ribbons were characterized by zone structure with zones about 10 nm and 4 nm in size. The isothermal aging of quenched samples resulted in the formation of modulated microstructure dissimilar to those of the optimal state. The coarsening of ferromagnetic beta particles as well as deterioration of the magnetic insulation of beta particles occur in bulk samples after aging at T-ag > 700 degrees C that decreases H-c <= 350 Oe. The dependence delta(M)(H) was measured and negative values of delta(M)(H) in the H=0-2000 Oe range indicate that magnetostatic interactions between the beta particles are dominant. The melt spun ribbons were characterized by the presence of antiphase domain boundaries (APD) and discontinuous precipitation (DP) products at grain boundaries (GB). The cellular areas at GBs consisting of alternating lamellas of beta'- and beta(2)' type phases were formed after aging the ribbons at T-ag > 500 degrees C. At T-ag > 700 degrees C. the modulated structure formed inside grains and the wide intergranular double-layer of beta and beta(2) phases develops by the coalescence of the primary DP products that decrease H-c <= 250 Oe. MFM image of the magnetic structure correlated with the microstructure of the ribbon. The coarse domains were observed in the wide intergranular layer of beta phase. The fine scale domains observed inside the grains indicates the magnetic domains formed as a result of magnetic interaction between the beta particles. (C) 2015 Elsevier B.V. All rights reserved.