报告主题：Dy-free high coercivity Nd-Fe-B permanent magnets
报告人：Kazuhiro Hono
时间：2016年04月22日(周五) 14:00
地点：曹光彪楼326会议室
邀请人：严密 教授
Kazuhiro Hono received the BS and MS degrees in Materials Science from Tohoku University in 1982 and 1984, respectively, and a Ph.D. degree in Metals Science and Engineering from Penn State in 1988. After working as a post doc at Carnegie Mellon, he became a research associate at the Institute for Materials Research, Tohoku University in 1990. He moved to the National Research Institute for Metals (currently National Institute for Materials Science, NIMS) as a senior researcher in 1995, and is now a NIMS Fellow and the Director of the Magnetic Materials Unit. He is also a professor in Materials Science and Engineering at the Graduate School of Pure and Applied Sciences, University of Tsukuba. His current research interest is materials science in magnetic and spintronics materials and their devices. He is also active in the development of high performance permanent magnets without critical elements.
Abstract：Due to the recent concern about the stable supply of heavy rare earth elements, attaining high coercivity in Nd-Fe-B magnets without Dy has received intense research interest. In this talk, we will update our recent progresses toward the development of high coercivity Nd-Fe-B permanent magnets. To obtain complete understanding of the microstructure-coercivity relationships, we revisited the microstructures of Nd-Fe-B sintered and hot-deformed magnets using aberration-corrected STEM complemented by atom probe tomography (APT). We found that the structure and chemical composition of the grain boundary phase varies depending on the orientation of grain boundaries, i.e., the grain boundary phase parallel to the c-planes are mostly crystalline with a higher Nd concentration in contrast to that lying parallel to the c-axis that contains higher Fe content with an amorphous structure. Based on these new findings, we developed a method to increase the coercivity of the anisotropic Nd-Fe-B magnets substantially without relying on Dy.
