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Considering that both La2Fe14B and Ce2Fe14B compounds exhibit similar weak temperature-dependent anisotropic fields (HA) as Y2Fe14B, this work aims to clarify the elevated temperature behavior of melt-spun nanocrystalline La- or Ce-partially substituted stoichiometric Y2Fe14B alloys containing no critical rare earth elements. The results show that La-substituted (Y1−xLax)2Fe14B alloys (x = 0–0.5) show exceptional elevated temperature behavior, manifested by the increased coercivity with increasing temperature. For the Ce-substituted (Y1−xCex)2Fe14B alloys, only x = 0.1 and 0.2 alloys show the similar trend. Both the temperature coefficient of remanence α and coercivity β can be improved by La-substituted, indicating partial substitution La can effectively enhance the thermal stability of Y2Fe14B alloy. However, excess La or Ce substitution would reduce α and β value, resulting in the deterioration of thermal stability. Highest β values of 0.05 and − 0.08 have been obtained in (Y0.9La0.1)2Fe14B alloy at 300–400 K and (Y0.8La0.2)2Fe14B alloy at 300–500 K, respectively. In addition, Ce substitution can effectively enhance the coercivity of Y2Fe14B alloy at room temperature and La substitution does not show a beneficial effect on the room-temperature magnetic properties. This work is beneficial for developing high-performance/cost ratio permanent magnets based on abundant rare earth elements with superior thermal stability. [ABSTRACT FROM AUTHOR]

Optimized shape anisotropy of the Fe-Co rich ferromagnetic (α 1) phase and the effective separation of the α 1 and α 2 phases with maximum magnetization difference—where α 2 represents a paramagnetic magnetic phase—are the key parameters for maximizing the magnetic properties of Alnico magnets. In this manuscript, efforts have been undertaken to optimize the shape anisotropy of the α 1 phase and increase the difference in magnetization and separation between α 1 and α 2 phases by fine tuning Al and Ni contents, directional solidification and magnetic field annealing methods. At first, Alnico magnets were fabricated by adjusting the content of α 2 phase followed by homogenization, magnetic field annealing at high temperature, and low-temperature tempering. Intrinsic coercivity (H cj) of ⁓146.0 kA/m, remanence (B r) of ⁓0.90 T and maximum energy density ((BH) max) of 46.02 kJ/m3 are achieved in the magnet with 8.2 wt% Al and 12.8 wt% Ni treated in field of 1.5 T for 10 minutes. At the second stage, the magnet with optimal magnetic properties is directionally solidified to develop columnar grains, and then the α 1 phase is grown in the direction of the columnar grains by magnetic field annealing to enhance the (BH) max to 79.8 kJ/m3. The axial ratio of the α 1 phase increased significantly with the increase of the grain size, particularly in the directionally solidified magnets. The Curie temperature of the α 1 phase is noted near 1150 K, while the Curie temperature of the α 2 phase is below 400 K. The magnets demonstrated excellent temperature stability, with magnetic properties decreasing by only 10–12 % at 800 K. These results may pave the way for further development of Alnico magnets specifically for high temperature applications. • Alnico 8 magnets are prepared by composition optimization, directional solidification and magnetic field annealing. • The biased growth of the Fe-Co phasedepends on the magnetic field and orientations of the main phase grains. • Shape anisotropy of Fe-Co phase and magnetization difference between the Fe-Co and Al-Ni rich phases are optimized. • High remanence of ∼1.1 T and high magnetic energy density of ∼80 kJ/m3 are obtained in directionally solidified magnets. • The magnets illustrate striking temperature stability up to 800 K. [ABSTRACT FROM AUTHOR]

Developing Ce, La, or Y based rare earth (RE) permanent magnets is a practical way to balance the utilization of RE resources. In this work, Y substitution for Ce and La is found to not only enhance the hard magnetic properties, but also significantly increase the Curie temperature T c and thermal stability of the melt-spun (Ce 0.7 La 0.3) 2 Fe 14 B alloys. To further optimize the magnetic performance, the RE-rich alloy with [(Ce 0.7 La 0.3) 0.8 Y 0.2 17 Fe 78 B 6 composition has been prepared. The good combination of magnetic properties with maximum energy product (BH) max = 7.1 MGOe, intrinsic coercivity H cj = 357 kA/m, and remanent polarization J r = 0.70 T has been obtained, together with low temperature coefficients of remanence (α = −0.255%/K) and coercivity (β = −0.246%/K). Importantly, RE element segregation has been confirmed in RE-rich (Ce,La,Y)–Fe–B alloys by microstructure and composition analysis. La prefers to enter into the intergranular phase than Ce and Y prefers to remain in the hard magnetic main phase, which results in increased T c , improved magnetic properties, and enhanced thermal stability. • A new high-abundance Ce/La/Y-based permanent magnets have been developed. • A good combination of magnetic properties can be obtained in (Ce,La,Y)–Fe–B alloys. • RE element segregation has been confirmed in RE-rich (Ce,La,Y)–Fe–B alloys. • La element prefers to enter into the intergranular phase than Ce element. • Y element likes to remain in the hard magnetic 2:14:1 phase. [ABSTRACT FROM AUTHOR]