Bulk glassy alloys in (Fe, Co, Ni)-Si-B system

Multicomponent Fe_75-x-yCo_xNi_ySi₈B ₁₇ glassy alloys were found to exhibit a distinct glass transition, followed by a supercooled liquid region before crystallization in a rather wide composition range of 7.5 to 45 at%Co and 7.5 to 60 at%Ni. The largest value of the supercooled liquid region defined by the difference between the glass transition temperature (T_g) and crystallization temperature (T_x), ΔT_x (= T_x - T_g) was 54 K for Fe₃₀Co₃₀Ni₁₅Si₈B₁₇. Furthermore, the high reduced glass transition temperature (T_g/T_m) above 0.60 was obtained in the range of 15 to 30 at%Co and 37.5 to 52.5 at%Ni in the series of Fe_75-x-yCo_xNi_ySi₈B ₁₇. The use of Fe₃₀Co₃₀Ni₁₅Si₈B₁₇ with a large ΔT_x of 54 K and a hig h T_g/T_m of 0.65 enabled us to produce bulk glassy rods with diameters up to 1.2 mm. The T_g, T_x, saturated magnetization (4π I_s), and coercive force (H_cj) of the as-cast 1.2 mm rod alloy are 780 K, 834 K, 0.90 T and 3.0 A/m, respectively. In addition, the cast glassy rod exhibits Young's modulus of 110 GPa, compressive fracture strength of 2800 MPa and fracture elongation of 1.9%. It is noticed that the thermal stability, magnetic properties and mechanical properties are nearly the same as those for the melt-spun glassy ribbon. The first synthesis of Fe-Si-B base bulk glassy alloys with good soft magnetic properties and high mechanical strength is promising for the future development as a new type of engineering material.