Bulk Glassy Alloys in (Fe, Co, Ni)-Si-B System

Abstract

Multicomponent Fe 75-x-y Co x Ni y Si 8 B 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 54K for Fe 30 Co 30 Ni 15 Si 8 B 17 . 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-y Co x Ni y Si 8 B 17 . The use of Fe 30 Co 30 Ni 15 Si 8 B 17 with a large ΔT x of 54K and a high 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 780K, 834 K, 0.90T, and 3.0A/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.