Presentation Information
[P1-12]Coercivity enhancement of Nd-Fe-B sintered magnet through grain boundary restructuring using Dy80Ga20 eutectic alloy
*PAULRAJ S1, VIVEKANANDHAN P1, VIJAYARAGAVAN G1, SADHASHIVAM M2, PRADEEP K. G.2, PRABHU D1, GOPALAN R1 (1. Centre for Automotive Energy Materials, International Advanced Research Centre for Powder Metallurgy and New Materials, Chennai – 600 113, Tamil Nadu, India (India), 2. Deptartment of Metallurgical and Materials Engineering, Indian Institute of Technology Madras (IITM), Chennai – 600 036, Tamil Nadu, India (India))
Keywords:
Sintered Nd-Fe-B magnet,Grain boundary diffusion,Dy80Cu20 alloy,Magnetic properties
Abstract
The sintered Nd-Fe-B magnets, invented by Sagawa in 1983, is unrivalled in terms of its high energy product [1]. The typical operating temperature of traction motors used in electric vehicles is about 150°C and addition of heavy rare earth (HRE) is necessary to retain the coercivity of these magnets to be used for these applications. Partial addition of Dy/Tb for Nd at the alloying stage is one of the approaches to enhance the coercivity of sintered magnet. However, high cost and the scarcity of Dy/Tb elements has always been a limitation. Grain boundary diffusion process (GBDP) is the one of the best routes to improve the coercivity with relatively less consumption of HRE [2-3]. In this work, we report relatively high coercivity obtained using a novel GBDP of Dy80Ga20 eutectic source. A coercivity enhancement of 113% yielding a coercivity value of 3.4 T was achieved under optimized conditions. GBDP carried out on the same magnet using one of the well reported Dy70Cu30 source only yielded ~78% enhancement in coercivity demonstrating the efficacy of the new alloy in enhancing the coercivity. Preliminary results suggest that the diffusion depth of Dy-Ga source is much higher as Ga is known to promote efficient diffusion of RE elements from the triple junctions [4]. In this presentation we shall detail the optimization parameters and report the evolution kinetics of the core shell microstructure and analyze the role of grain boundary chemistry using 3-Dimensional atom tomography and transmission electron microscopy studies.
References:
1. Sagawa, S. Fujimura, N. Togawa, H. Yamamoto, Y. Matsuura, Journal of Applied Physics, 55 (1984) 2083. Hono, H. Sepehri-Amin, Scripta Materialia, 67 (2012) 530.
2. Wang, T. T. Sasaki, Y. Une, T. Ohkubo, K. Hono, Acta Materialia, 248 (2023) 118774
3. Huang, Q. Jiang, Y. Shi, S. Ur Rehman, D. Shi, G. Fu, Z. Li, D. Xu, D. Chen and Z. Zhong, Journal of Magnetism and Magnetic Materials, 552 (2022) 169242
Figure Caption
Figure. 1 Variation of intrinsic coercivity and remanent magnetization in Dy80Ga20 diffused Nd-Fe-B magnet at different annealing duration
The sintered Nd-Fe-B magnets, invented by Sagawa in 1983, is unrivalled in terms of its high energy product [1]. The typical operating temperature of traction motors used in electric vehicles is about 150°C and addition of heavy rare earth (HRE) is necessary to retain the coercivity of these magnets to be used for these applications. Partial addition of Dy/Tb for Nd at the alloying stage is one of the approaches to enhance the coercivity of sintered magnet. However, high cost and the scarcity of Dy/Tb elements has always been a limitation. Grain boundary diffusion process (GBDP) is the one of the best routes to improve the coercivity with relatively less consumption of HRE [2-3]. In this work, we report relatively high coercivity obtained using a novel GBDP of Dy80Ga20 eutectic source. A coercivity enhancement of 113% yielding a coercivity value of 3.4 T was achieved under optimized conditions. GBDP carried out on the same magnet using one of the well reported Dy70Cu30 source only yielded ~78% enhancement in coercivity demonstrating the efficacy of the new alloy in enhancing the coercivity. Preliminary results suggest that the diffusion depth of Dy-Ga source is much higher as Ga is known to promote efficient diffusion of RE elements from the triple junctions [4]. In this presentation we shall detail the optimization parameters and report the evolution kinetics of the core shell microstructure and analyze the role of grain boundary chemistry using 3-Dimensional atom tomography and transmission electron microscopy studies.
References:
1. Sagawa, S. Fujimura, N. Togawa, H. Yamamoto, Y. Matsuura, Journal of Applied Physics, 55 (1984) 2083. Hono, H. Sepehri-Amin, Scripta Materialia, 67 (2012) 530.
2. Wang, T. T. Sasaki, Y. Une, T. Ohkubo, K. Hono, Acta Materialia, 248 (2023) 118774
3. Huang, Q. Jiang, Y. Shi, S. Ur Rehman, D. Shi, G. Fu, Z. Li, D. Xu, D. Chen and Z. Zhong, Journal of Magnetism and Magnetic Materials, 552 (2022) 169242
Figure Caption
Figure. 1 Variation of intrinsic coercivity and remanent magnetization in Dy80Ga20 diffused Nd-Fe-B magnet at different annealing duration
