Development of an (Fe, Sn)-based Nanocrystalline Soft Magnetic Alloy

Abstract

The D03 Fe3Sn phase shows higher magnetization and smaller magnetocrystalline anisotropy compared to Fe3Si based on the comprehensive first principles calculations [1]. A new computation-based alloy design method, motivated by the work of Villars [2], was used to design a new alloy system (Fe1-x-yCoxSny)87Nb3B9Cu1 (4<x<27, 5<y<15) to achieve D03 Fe3Sn phase with the help of the melt-spinning process. Differential scanning calorimetry was used to determine the primary crystallization temperatures of the Fe79-xCoxSn8Nb3B9Cu1 alloys (x=4, 9, 14, 19 and 24), which have peak temperatures from 405°C to 420°C at a heating rate of 10°C /min. The amorphous ribbons were encapsulated in fused quartz ampoules and annealed in tube furnace at 450°C, 500°C, or 550 °C for 3600 seconds. X-Ray Diffraction (XRD) has been used to analyze structural properties of as-spun and heat-treated ribbons of all alloy compositions. Partial crystalline exists during the melt-spinning process for these series alloys except the Fe60Co20Sn7Nb3B9Cu1 as-spun ribbons, which has a single broad scattering peak of XRD diffractograms indicating an amorphous phase. XRD diffractogram of the heat-treated ribbons are comprised of a B2 phase, which has a primitive cubic structure. The crystallite sizes for each heat-treated sample were estimated by Scherrer broadening to have values between 6 and 11 nm. The magnetic properties of as-spun and heat-treated ribbons were studied by vibrating sample magnetometry. Saturation magnetization and coercivity were determined from room temperature magnetic hysteresis loops. The highest magnetization value 171.4 Am2/kg was achieved by Fe60Co22Sn5Nb3B9Cu1 alloy annealed at 500°C while the coercivity value is 67.3A/m.