Reducing Dy content by Ce substitution in nanocomposite Nd-Dy-Fe-B/α-Fe alloys

Highlights: • Abundant element Ce is used to substitute Dy in [Nd_0.8Dy_0.2]₁₀Fe_82.5B₆Zr_1.5 alloy. • Optimal magnetic properties are obtained in the alloy with 50% Dy reduction. • 20% Ce substituting Dy leads to an abnormally increased coercivity and stability. • Effects of Ce on Curie temp., thermal stability and exchange coupling are studied. To alleviate Dy and Tb shortage and develop permanent magnets with high performance/cost ratio, the abundant and inexpensive rare earth (RE) element Ce has been suggested to be employed in Nd-Fe-B alloys. In this work, the effects of Ce substitution for Dy on the microstructure, magnetic properties, and thermal stability of melt spun nanocomposite [Nd_0.8(Dy_1-xCe_x)_0.2]₁₀Fe_82.5B₆Zr_1.5 alloys are systematically investigated. The refined XRD results show the existence of 2:14:1 phase and α-Fe in all alloys, and the c-axis expansion for the 2:14:1 phase is observed in the alloy with x = 0.2. With Ce substitution, the alloys exhibit a lightly increased grain size and more uniform microstructure. An abnormal increase of coercivity H_c = 833 kA/m and a sudden decrease of temperature coefficients of coercivity |β| = 0.323%/°C are observed in x = 0.8 alloy, which is only slightly lower than those of x = 0.25 alloy, 865 kA/m and 0.321%/°C, respectively. With increasing Ce content, the Curie temperature T_c of 2:14:1 phase monotonically decreases from 550 K to 535 K, and the exchange coupling effect is weakened. The [Nd_0.8(Dy_0.5Ce_0.5)_0.2]₁₀Fe_82.5B₆Zr_1.5 alloy with 50% Dy reduction exhibits a high (BH)_max of 133 kJ/m³ with an acceptable β value of −0.348%/°C and an H_c of 769 kA/m. It is expected that these investigations could be beneficial for developing Ce-containing nanocrystalline Nd-Fe-B magnets with saved heavy RE resources.