Tripling in coercivity (Hc) for the thermal and structural highly stabilized MnAlBi-C rare earth free permanent magnet via Bi doping

作者：Fang, H. L.^*; Liu, J.^*; Huang, P. W.; Shi, D. W.

来源：MATERIALS & DESIGN, 2023, 230: 111887.

DOI：10.1016/j.matdes.2023.111887

• Permanent magnet
• Coercivity
• MnAl
• LTP MnBi
• Metastable

The limited coercivity (Hc) and metastability of the ferromagnetic s phase MnAl-C magnet have constrained its magnetic performance and application potential. Bi was doped into the Mn54Al44-xBixC2 alloy system in this study. The doped Bi could effectively stabilize the metastable s phase and inhibit the nonmagnetic Al-rich phase formation. The ferromagnetic s phase ratio increased dramatically as the doped Bi increase, with a peak Ms of 81 emu/g was achieved for the post-annealed Mn54Al43.6Bi0.4C2 alloy at 19 kOe. High Hc ferromagnetic LTP MnBi phase forms within the Mn54Al44-xBixC2 (x = 0.2, 0.4, 0.6) alloys when it been annealed at 300celcius for 24 h, the samples tripled or even quadrupled in Hc compared with the initial synthesized alloy. The doped Bi dissolved within lattice caused the s phase thermally stability, structural stability improves substantially; 0.4 Bi doped Mn54Al43.6Bi0.4C2 alloy exhibited a combination of high Ms and Hc even after been ball milled for a long period of 15 and 20 h. The (Ms, Hc) achieved a value of (59.6 emu/g, 3526 Oe) for the 15 h milled sample and (51.5 emu/g, 4546 Oe) for the 20 h milled sample at 19 kOe, respectively; which is desirable for its application as a high-performance rare earth free permanent magnet.& COPY; 2023 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).