Nanocrystalline MnAlV rare-earth-free Permanent Magnetic Alloys with Improved Magnetization and Thermal Stability

Abstract

Ferromagnetic τ-MnAl alloy with attractive magnetic properties has been considered as one of the most promising rare-earth-free permanent magnetic materials. However, there are difficulties in obtaining the high-purity τ-MnAl alloy. In this study, the crystallographic structure, phase transformation and magnetic properties of nanocrystalline MnAlV alloys prepared by the melt-spinning technique were systematically investigated. The results showed that the phase composition, microstructure and magnetic properties were tailored by V doping in the MnAl alloys. V doping was effective in promoting the formation of the τ phase in the as-spun MnAl alloy during the melt-spinning process. In addition, V doping improved the thermal stability of ε phase and τ phase in MnAl alloys, which was derived from the different atomic radii and negative mixing enthalpy. As a result, the high-purity τ phase with a saturation magnetization of 120.5 emu/g and coercivity of 1030 Oe was achieved in the Mn53.35Al43.65V3 alloy. Therefore, this work contributed to the design and preparation of nanocrystalline τ-MnAl rare-earth-free permanent magnetic materials.