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

Abstract

Multicomponent Fe75-x-yCoxNiySi8B 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 (Tg) and crystallization temperature (Tx), ΔTx (= Tx - Tg) was 54 K for Fe30Co30Ni15Si8B17. Furthermore, the high reduced glass transition temperature (Tg/Tm) 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 Fe75-x-yCoxNiySi8B 17. The use of Fe30Co30Ni15Si8B17 with a large ΔTx of 54 K and a hig h Tg/Tm of 0.65 enabled us to produce bulk glassy rods with diameters up to 1.2 mm. The Tg, Tx, saturated magnetization (4π Is), and coercive force (Hcj) 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.