Effect of Si on the glass-forming ability, thermal stability and magnetic properties of Fe–Co–Zr–Mo–W–B alloys

This paper presents investigations on the effect of Si on the glass-forming ability, thermal stability and magnetic properties of the Fe–Co–Zr–Mo–W–B samples (group I: Fe60Co8Zr10Mo5W2B15−xSix, 1 ≤ x ≤ 4; group II: Fe60Co8Zr10−xMo5W2B15Six, 0 ≤ x ≤ 4; group III: Fe60Co8Zr8Mo5W2B17−xSix, 0 ≤ x ≤ 2) prepared by melt spinning, injection casting, and centrifugal casting methods. It is found that the glass-forming ability (GFA) of the alloys in group I is more deteriorated than that in group II, and that the alloys in group III can be cast into the rods of 1–3 mm diameter without crystalline reflections in their XRD patterns. For the amorphous ribbons and rods, a non-monotonic change of the nearest neighbour distance r1 with increasing Si content cSi was detected, which is parallel to that of the glass transition and crystallization temperatures Tg and Tx, but opposite to that of the magnetization at room temperature MRT and the Curie temperature Tc. This correlation can be interpreted by a structure model presuming that iron atoms appear simultaneously in two types of local structures in the amorphous samples.