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 Fe 70-x Co 10 Pr x B 20 (0 ≤ x? 6) amorphous alloys have been investigated. The glass transition followed by a supercooled liquid region (ΔT x ) was observed in the composition range of 2 to 5 at%Pr and the value of the ΔT x 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 ΔT x and reduced glass transition temperature (T g /T m ) of the 3.5 at%Pr alloy are 43 K and 0.57, respectively. The crystallized structure consists of (Fe, Co) 3 B, α-(Fe, Co) and Pr 2 (Fe, Co) 4 B phases and their average grain sizes after annealing for 420s at 863K are about 25 nm. The remanence (B r ), coercivity ( i H c ) 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/m 3 , 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.