DSC, XRD and TEM characterization of glassy Co40Fe22Ta8B30 alloy with very high thermal stability

In this letter we report about a new melt-spun Co40Fe22Ta8B30 metallic glass with a wide supercooled liquid region of 74 K. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) investigations confirmed that crystallization occurs with significantly longer incubation time during annealing above the glass transition, as compared to the well-known Co43Fe20Ta5.5B31.5 glassy alloy. The new alloy as a good soft magnetic material showed a very low coercivity of 0.8 A/m and polarization of 0.5 T. The origin of high thermal stability was attributed to the formation of Ta–Ta bonds in the microstructure and the absence or very low quantity of Ta-based units with the composition close to the stoichiometry of the (Co,Fe)21Ta2B6 crystalline phase.

► New glassy ribbon with a wide supercooled liquid region of 74 K was produced.
► Very high incubation time before crystallization was attained.
► The new alloy shows very low coercivity of 0.8 A/m and polarization of 0.5 T.