Rapidly quenched heavy rare earth-based ternary Lu-Fe-B alloys: Phase evolution and hard magnetic properties

Abstract

Aiming to clarify the fundamental properties of Lu-Fe-B alloys and facilitate the application of the Lu in rare earth (RE)-iron-boron permanent magnets, the phase constitutions, phase precipitation behavior, and hard magnetic properties of Lu12+xFe82−xB6 alloys (x = 0–4) prepared by melt spinning were systematically studied. The intrinsic coercivity Hcj= 313 kA/m, remanence Jr = 0.72 T, and maximum energy product (BH)max= 68.5 kJ/m3 were obtained in optimally quenched Lu12Fe82B6 alloy. Different from many other RE-Fe-B alloys, increasing Lu content leads to the formation of the soft magnetic amorphous phase and Lu6Fe23 phase, which eventually increases the exchange coupling effect and decreases Hcj and (BH)max of the Lu-rich alloys (x = 1–4). For the amorphous Lu12+xFe82−xB6 alloys, after annealing treatment, Lu2Fe14B and Fe2B phases precipitate in the alloys with x = 0 and 1, but the crystalline phases change into Lu6Fe23, Lu2Fe14B, and Fe2B phases in the alloys with x = 2–4. For the Lu-rich alloys, all crystalline phases tend to precipitate simultaneously from the amorphous matrix, which is beneficial to obtaining optimized microstructure under various processes. The alloy with x = 2 annealed at 750 °C for 10 min exhibits a good combination of magnetic properties with Jr = 0.69 T, Hcj= 234 kA/m, and (BH)max= 51.9 kJ/m3. The present results can serve as a useful reference for promoting the utilization of Lu in RE permanent magnets.