F. Bao, Y.H. Li, Z.W. Zhu, X.Y. Liang, Y. Zhang, W. Zhang. J. Iron Steel Res. Int., 2021, 28, 597-603.

Abstract:

Soft magnetic Co-based Co–Y–Nb–B bulk metallic glasses (BMGs) without Fe have been developed by micro-alloying Y and Nb into a Co₇₅B₂₅ alloy. First, addition of 3–4 at.% Y promotes the occurrence of glass transition and increases the supercooled liquid stability and magnetic softness. Co_71.5Y_3.5B₂₅ metallic glass possesses a large supercooled liquid region (ΔT_x) of 33 K and low coercivity (H_c) of 1.5 A/m. Subsequent alloying 2–4 at.% Nb into Co_71.5Y_3.5B₂₅ alloy further enlarges ΔT_x to 50 K, lowers H_c to 0.9 A/m, and enables the formation of BMGs with a critical sample diameter up to 2.0 mm. The alloying Nb causes the formation of complex (Co, Nb, Y)₂₃B₆ competing phase during crystallization and widens the melt undercooling during solidification, which improves the supercooled liquid stability and glass-forming ability, respectively. Co–Y–Nb–B BMGs also exhibit good soft magnetic and mechanical properties, i.e., low H_c of 0.9–1.2 A/m, relatively high saturation magnetic flux density of 0.36–0.57 T, high yielding strength of 3877–3930 MPa with plastic strain of 0.2%–0.3%, and high Vickers hardness of 1156–1201. The developed soft magnetic Co-based BMGs are promising for applications as structural and functional materials.

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