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Cobalt-based bulk glassy alloy with ultrahigh strength and soft magnetic properties

Abstract

Bulk metallic glasses—formed by supercooling the liquid state of certain metallic alloys—have potentially superior mechanical properties to crystalline materials. Here, we report a Co43Fe20Ta5.5B31.5 glassy alloy exhibiting ultrahigh fracture strength of 5,185 MPa, high Young's modulus of 268 GPa, high specific strength of 6.0 × 105 Nm kg−1 and high specific Young's modulus of 31 × 106 Nm kg−1. The strength, specific strength and specific Young's modulus are higher than previous values reported for any bulk crystalline or glassy alloys1,2,3. Excellent formability is manifested by large tensile elongation of 1,400% and large reduction ratio in thickness above 90% in the supercooled liquid region. The ultrahigh-strength alloy also exhibited soft magnetic properties with extremely high permeability of 550,000. This alloy is promising as a new ultrahigh-strength material with good deformability and soft magnetic properties.

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Figure 1: True stress–strain curves of bulk glassy Co43Fe20Ta5.5B31.5 alloy rods with a diameter of 2 mm tested under a compressive applied load at various temperatures between room temperature and 873 K.
Figure 2: HRTEM images of bulk glassy Co43Fe20Ta5.5B31.5 alloy rods with a diameter of 2 mm.
Figure 3: SEM image revealing the deformation and fracture behaviour of the bulk glassy Co43Fe20Ta5.5B31.5 alloy rod with a diameter of 2 mm deformed up to a true strain of 0.021 at 698 K.

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Correspondence to Akihisa Inoue.

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Inoue, A., Shen, B., Koshiba, H. et al. Cobalt-based bulk glassy alloy with ultrahigh strength and soft magnetic properties. Nature Mater 2, 661–663 (2003). https://doi.org/10.1038/nmat982

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