Presentation Information
[P1-13]Nb assisted grain boundary pinning in Nd-Cu diffused Nd-Fe-B magnets for enhancing the Coercivity
Sivakumar Munibhaskar1, Prabhu Delhi Babu2, Pradeep KG1, *Gopalan Raghavan2 (1. Indian Institute of Technology, Madras, Chennai-600036 (India), 2. International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), IITMadras Research Park, Chennai-600113 (India))
Keywords:
Nd-Fe-B,coercivity,microstructure,melt-spinning,magnetic properties
Grain boundary diffusion process (GBDP) using low-melting eutectic alloys is an effective method to enhance the coercivity of Nd-Fe-B permanent magnets by enriching grain boundaries (GBs) with Nd and other low-melting elements. However, the accompanying grain growth during annealing often has an adverse impact on coercivity. To overcome this, alloying with Nb has been introduced to impede grain growth while maintaining a fine microstructure during GBDP. Melt-spun ribbons of Nd-Fe-B alloys with Nb doping provide a favourable microstructure, as the rapid solidification process produces fine grains and a homogeneously distributed Nb-rich phase. Therefore, GBDP in Nd-Fe-Nb-B can be advantageous. Here we report the GBDP of Nd-Cu eutectic phase and the influence of Nb on the microstructure and magnetic properties of Nd-Fe-B melt-spun ribbons. The coercivity was enhanced from 1.2 T to 2.1 T with Nd-Cu GBDP. Coercivity enhancement mechanisms were evaluated in detail through magnetic measurements, microstructural characterization, and advanced techniques such as transmission electron microscopy (TEM), exchange coupling analysis, and atom probe tomography (APT). The results provide insights into the synergistic role of Nb-rich clusters and Nd-Cu-enriched GBs in suppressing grain growth and promoting domain wall pinning. The detailed microstructure and magnetic properties of the Nd-Cu GBDP Nd-Fe-Nb-B would be discussed[1] H. Sepehri-Amin, D. Prabhu, M. Hayashi, T. Ohkubo, K. Hioki, A. Hattori, K. Hono, , Scripta Materilia, 68, 167 (2013)[2] M.B Sivakumar, D.Prabhu, M. Sadhasivam, B. Manjusha, N. Chandrasekaran, K.G. Pradeep, G. Sundararajan and R. Gopalan, Materials Research Letters, 10(12), 780 (2022)
