Structure and magnetic properties of melt-spun Fe-Pt-B alloys with high B concentrations

The phase evolution, thermal stability, structure and magnetic properties of the melt-spun Fe70-xPtxB30 (x = 0-20) alloys have been investigated. Addition of small amounts of Pt to the Fe70B30 alloy increases the amorphous-forming ability, leading to the formation of an amorphous phase in the alloys with x = 5 and 10. Further increase in Pt content results in the formation of the fcc-FePt + Fe2B or fcc-FePt + L1(0)-FePt + Fe2B crystalline phases. After appropriate annealing, the homogeneous nano-sized structure consisting of hard L1(0)-FePt and soft Fe2B magnetic phases were formed for the alloys with x = 10-20, which exhibited good hard magnetic properties. As the Pt content increase, the coercivity (iH(c)) of the L1(0)-FePt/Fe2B nanocomposite alloys significantly increased, while the remanence (B-r) decreased. The B-r, reduced remanence (M-r/M-s), iH(c), and energy product (BH)(max) of the alloys are in the range of 0.81-1.20 T, 0.76-0.84, 173.2-523.1 kA/m, and 64.0-88.3 kJ/m(3), respectively. (C) 2014 Elsevier B.V. All rights reserved.