Compositional correlations to intrinsic magnetic properties in binary and Ti-alloyed MnAl magnetic alloys

• Published in: Journal of iron and steel research, international international, 2024-12, Vol.31 (12), p.3058-3068
• Main Authors: Zhao, Shuang, Dong, Ying, Jia, Yu-xiao, Xu, Yi-chen, Wu, Yu-ye
• Format: Article
• Language: English
• Subjects: Applied and Technical Physics; Engineering; Machines; Manufacturing; Materials Engineering; Materials Science; Metallic Materials; Original Paper; Physical Chemistry; Processes
• ISSN: 1006-706X; 2210-3988
• DOI: 10.1007/s42243-024-01239-w

MnAl rare-earth-free permanent magnets exhibit excellent advantages from economic and resource perspectives, which have attracted extensive attentions in recent decades. We reported the evolution in phase formation and intrinsic magnetic properties of τ-phase in binary MnAl alloys with the variation in Mn:Al ratios. Ferromagnetic τ-phase can be generated within the compositional range of Mn 50+ x Al 50− x ( x  = 1–8), and pure τ-phase can only be obtained in the alloys with x  = 4–7. With Mn:Al ratio increasing, saturation magnetization M s and magnetocrystalline anisotropy constant K 1 are gradually weakened due to the incremental antiferromagnetic Mn-1 d atoms, but Curie temperature of τ-phase is gradually increased induced by the strengthened d−d hybridization of Mn 1 a −Mn 1 d . An attempt of doping traces of Ti was carried out in order to eliminate the negative antiferromagnetic interaction derived from Mn-1 d atom. Ti atoms tend to occupy 1 d sites and replace the Mn-1 d atoms due to the relatively fewer valence electrons compared with Mn, resulting in the reduction in Mn 1 a −Mn 1 d antiferromagnetic interactions, which is demonstrated by the higher M s of Mn 55− y Al 45 Ti y ( y  = 1) than that of Mn 55 Al 45 . However, with further substitution of Mn by Ti, unfavorable κ-phase is unavoidably generated. Finally, the occupation preference and the corresponding influences on local magnetic interactions as well as the magnetizations of the different alloying atoms including interstitial element C, 3d atoms Ti, Co and Cu, and main-group element Ga are systematically summarized, in order to offer the guidance of designing MnAl permanent magnets with ideal magnetic properties.