Multicomponent Co-based Amorphous Alloys with Wide Supercooled Liquid Region

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Abstract
A ferromagnetic Co-based amorphous phase with a wide supercooled liquid region before crystallization was found to be formed in rapidly solidified Co70M3Al5Ga2P15B4C1 (M=Cr or V) and Co67Cr3Fe3Al5Ga2P15B4C1 alloys. The glass transition temperature (Tg) and crystallization temperature (Tx) are in the ranges of 717 to 722 K and 766 to 768 K, respectively, and the temperature interval of the supercooled liquid region defined by the difference between Tg and Tx is 45 to 51 K. This is believed to be the first evidence on the appearance of Co-based amorphous alloys with the distinct glass transition and a wide supercooled liquid region. The crystallization takes place through a single stage resulting from the precipitation of four kinds of phases Co, Co2P, Co4B and Co3C. The crystallization process implies the necessity of a long-range rearrangement of constituent elements in the supercooled liquid. The necessity seems to be closely related to the increase in the thermal stability of the supercooled liquid through the retardation of the precipitation of the four crystalline phases. These Co-based amorphous alloys exhibit soft ferromagnetism with Curie temperatures ranging from 365 to 420 K. The saturation magnetization, coercivity and permeability at 1 kHz are in the range of 0.27 to 0.34 T, 4.5 to 8.0 A/m and 4600 to 5800, respectively. From the combination of the soft magnetic properties and a wide supercooled liquid region, we can expect future development of Co-based amorphous alloys as a new soft magnetic material with large glass-forming ability and good viscous deformability.