Bulletin of the Polish Academy of Sciences: Technical Sciences

Abstract

GFA of the alloy [5][6][7]. Furthermore, doping with Zr and Nb causes the microstructure refinement of the RE-Fe-B magnets and, thus, can enhance the magnetic properties of the annealed specimens [8][9][10]. As was reported in [7], the appropriate setting of the composition for the Fe 67 Co 9.4 Nd 3.1 Dy 0.5 B 20 alloy led to an improvement of the GFA that allowed processing of the fully glassy rods with diameters up to 0.5 mm. A further change of composition and addition of Zr facilitated casting 1-mm diameter amorphous rods and up to 3-mm outer diameter tubes for the Fe 61 Co 13.5 Zr 1 Pr 3.5 Dy 1 B 20 alloy [11]. However, a small amount of RE elements in the chemical composition caused the formation of a relatively low fraction of the RE 2 Fe 14 B phase. For this reason, such magnets reveal rather moderate magnetic parameters [12]. We have shown in our previous studies on rapidly solidified plates of various thicknesses produced for Pr 9 Fe 50 + x Co 13 Zr 1 Nb 4 B 23 - x (x = 0, 2, 5, 8) alloys that boron content greatly influences the GFA. In the case of the Pr 9 Fe 50 Co 13 Zr 1 Nb 4 B 23 alloy, the 0.5-mm thick plates were fully amorphous while 1-mm plates were slightly crystalline and only one very low-intensity diffraction peak was detected [6,13]. However, for alloys of lower B content, the suction cast plates were all crystalline in as-cast state. Furthermore, the critical cooling rate attainable for specific production equipment depends on the sample geometry [14]. The changes in the microstructure and magnetic properties with the sample shape were shown for the Pr 9 Fe 52 Co 13 Zr 1 Nb 4 B 21 alloy [15].The aim of the present work was to study the influence of the Fe to B ratio on the GFA as well as on the phase constitution, microstructure, and magnetic properties of the 1-mm diameter rods of Pr 9 Fe 50 + x Co 13 Zr 1 Nb 4 B 23 - x (x = 0, 5, 8) alloys in the as-cast state and those subjected to annealing. Preliminary analysis of magnetic parameters has shown that optimal magnetic