Presentation Information
[P1-9]Utilization of high-abundance rare earth elements in Tb-Cu-Al alloy for high efficient grain boundary diffusion of Nd-Fe-B magnets
*Mingpeng Kou1, Hongya Yu1, Xichun Zhong1, Zhongwu Liu1 (1. School of Materials Science and Engineering, South China University of Technology (China))
Keywords:
Nd-Fe-B,Grain boundary diffusion,High-abundance rare earth elements,Diffusion behavior
Grain boundary diffusion (GBD) is an effective approach to enhance coercivity for Nd-Fe-B magnets with reduced consumption of heavy rare earths (HRE). Nevertheless, it is also confronted with the challenge of shallow diffusion depth, causing a low utilization efficiency of HRE. To address this issue, a significant portion of the current research efforts have been centered on promoting the diffusion effects of HREs along the GBs by replacing the HRE by light REs of Pr and Nd. In our previous work, we proposed the introduction of La and Ce into binary alloys of Tb, which achieved a remarkable improvement in the utilization efficiency of HRE due to synergistic effect of those three REs (Tb, Ce, La) , thereby inspiring the exploration of high-abundance RE as components of diffusion source. However, the diffusion behavior of high-abundant REs and the characteristics of elemental distribution are still unclear.
In this study, we systematically investigated the diffusion behavior of the La, Ce, Y in Tb-Cu-Al alloy, as well as the synergistic mechanism between La, Ce, Y and Tb, ultimately achieving the modulation of diffusion behavior of Tb by high-abundant REs. After the GBD process at 900 ℃ for 10 h, even though 25 at% of Tb is substituted by La, Ce, or Y, the coercivity enhancement (ΔHcj) of the Tb60La20Cu10Al10, Tb60Ce20Cu10Al10, Tb60Y20Cu10Al10 diffused magnet were 1.19 T, 1.12 T, 1.08 T, respectively, even higher than that of Tb80Cu10Al10 with ΔHcj of 1.01T. The BSE images and EDS mapping in Fig. 1 indicate that La tends to aggregate at grain boundaries while Ce and Y prefer to enter into the grains. Further analyses demonstrated that the notable performance enhancement of Tb60(La,Ce,Y)20Cu10Al10 diffused magnet is mainly attributed to the synergistic effect of La, Ce, Y on the diffusion of Tb. The competitive diffusion of Ce or Y and Tb effectively inhibited the lattice diffusion of Tb in the grains. La tends to combine with oxygen to form La2O3, which reduces the consumption of Tb in the grain boundary oxide, improving the effective function depth for magnetic hardening shell structure. This work provides insight for the design of low-cost diffusion alloy containing high-abundance rare-earths.
In this study, we systematically investigated the diffusion behavior of the La, Ce, Y in Tb-Cu-Al alloy, as well as the synergistic mechanism between La, Ce, Y and Tb, ultimately achieving the modulation of diffusion behavior of Tb by high-abundant REs. After the GBD process at 900 ℃ for 10 h, even though 25 at% of Tb is substituted by La, Ce, or Y, the coercivity enhancement (ΔHcj) of the Tb60La20Cu10Al10, Tb60Ce20Cu10Al10, Tb60Y20Cu10Al10 diffused magnet were 1.19 T, 1.12 T, 1.08 T, respectively, even higher than that of Tb80Cu10Al10 with ΔHcj of 1.01T. The BSE images and EDS mapping in Fig. 1 indicate that La tends to aggregate at grain boundaries while Ce and Y prefer to enter into the grains. Further analyses demonstrated that the notable performance enhancement of Tb60(La,Ce,Y)20Cu10Al10 diffused magnet is mainly attributed to the synergistic effect of La, Ce, Y on the diffusion of Tb. The competitive diffusion of Ce or Y and Tb effectively inhibited the lattice diffusion of Tb in the grains. La tends to combine with oxygen to form La2O3, which reduces the consumption of Tb in the grain boundary oxide, improving the effective function depth for magnetic hardening shell structure. This work provides insight for the design of low-cost diffusion alloy containing high-abundance rare-earths.
