Thermal stability and magnetic properties of Fe-Co-Pr-B amorphous alloys with a supercooled liquid region

Abstract

The thermal stability, crystallized structure and magnetic properties of melt-spun Fe70-xCo10PrxB20 (0 ≤ x ≤ 6) amorphous alloys have been investigated. The glass transition followed by a supercooled liquid region (ΔTx) was observed in the composition range of 2 to 5 at%Pr and the value of the ΔTx is in the range of 23 to 43 K. The good hard magnetic properties were obtained for the alloys containing 2.5 to 5 at%Pr subjected to an optimum heat treatment. The ΔTx and reduced glass transition temperature (Tg/Tm) of the 3.5 at%Pr alloy are 43 K and 0.57, respectively. The crystallized structure consists of (Fe,Co)3B, α-(Fe,Co) and Pr2(Fe,Co)4B phases and their average grain sizes after annealing for 420 s at 863 K are about 25 nm. The remanence (Br), coercivity (iHc) and maximum energy product (BH)max of the optimally annealed the 3.5 at%Pr alloy are 1.36 T, 211 kA/m and 107 kJ/m3, respectively. The good hard magnetic properties in the crystallized state of the Fe-Co-Pr-B amorphous alloys with high glass-forming ability indicates the possibility of future fabrication of a bulk hard magnetic material by the simple process of the formation of a bulk amorphous alloy followed by crystallization.