In this study,the influence of Ce-and Ce-La-substitution for Nd in Nd-Fe-B magnets on their magnetic and microstructural changes in the course of the hot-deformation process was investigated to gain insight into furth...In this study,the influence of Ce-and Ce-La-substitution for Nd in Nd-Fe-B magnets on their magnetic and microstructural changes in the course of the hot-deformation process was investigated to gain insight into further reducing the Nd content in fine-grained Nd-Fe-B hot-deformed magnets.We found that the[001]texture and microstructure of the RE-rich grain boundary phases,which are the factors that de-termine the remanence and coercivity of hot-deformed magnets,were deteriorated by the Ce-and Ce-La-substitution.This is because the volume fraction of the RE-rich liquid formed in the grain boundaries during the hot-press and hot-deformation decreased due to the Ce-and Ce-La-substitution,thereby in-creasing the friction between the 2:14:1 grains while the c-axes of grains were aligned by grain rotation and decreasing the RE concentration of grain boundary phases.In particular,the Ce-La-co-substitution further prevented the liquid formation within the grain boundaries of the magnets during hot-press and hot-deformation because the wettability of the RE-rich liquid on the 2:14:1 grains became poor when La was substituted for Nd in the 2:14:1 grains.These results indicate that there is room for further im-provement in both the remanence and coercivity of the Ce-and Ce-La-substituted magnets by intro-ducing additional liquid into the grain boundaries prior to hot-press and hot-deformation.By applying the Nd-Cu infiltration process to the melt-spun ribbons(intermediate infiltration,I-infiltration),both the remanence and coercivity of the Nd-saving(Nd 0.7 Ce 0.3)-Fe-B and(Nd 0.7 Ce 0.225 La 0.075)-Fe-B hot-deformed magnets were successfully improved.展开更多
A grain boundary diffusion process(GBDP)was adopted to improve magnetic properties of Dy-free highly coercive Nd-Fe-B permanent magnet by coating thin layers of Nd and Cu in grain boundaries.For GBDP of Nd and Cu,Nd a...A grain boundary diffusion process(GBDP)was adopted to improve magnetic properties of Dy-free highly coercive Nd-Fe-B permanent magnet by coating thin layers of Nd and Cu in grain boundaries.For GBDP of Nd and Cu,Nd and Cu were coated by wet process,e.g.,electrochemical and electroless on Nd-Fe-B magnets,which was fabricated by hot-deformed/die-upset with meltspun specimen.Heat treatment was performed for 20 min at 600℃followed by several different cooling conditions.The cooling conditions after heat treatment were varied to understand distribution and micros tructural effects of Nd and Cu species in grain boundaries.The coercivity increased from 1.565 to 1.637 T in oil cooling rate but remanence decreased,while remanence jumped with little decrease in coercivity in furnace cooling.Micros tructure analyses suggested that the coercivity was closely related to the cooling rate as well as distribution of Nd.The mechanism of coercivity enhancement due to the cooling rate was discussed based on the results presented here and those in the literature.展开更多
基金supported by the Fundamental Research Pro-gram of the Korea Institute of Material Science(No.PNK8310).
文摘In this study,the influence of Ce-and Ce-La-substitution for Nd in Nd-Fe-B magnets on their magnetic and microstructural changes in the course of the hot-deformation process was investigated to gain insight into further reducing the Nd content in fine-grained Nd-Fe-B hot-deformed magnets.We found that the[001]texture and microstructure of the RE-rich grain boundary phases,which are the factors that de-termine the remanence and coercivity of hot-deformed magnets,were deteriorated by the Ce-and Ce-La-substitution.This is because the volume fraction of the RE-rich liquid formed in the grain boundaries during the hot-press and hot-deformation decreased due to the Ce-and Ce-La-substitution,thereby in-creasing the friction between the 2:14:1 grains while the c-axes of grains were aligned by grain rotation and decreasing the RE concentration of grain boundary phases.In particular,the Ce-La-co-substitution further prevented the liquid formation within the grain boundaries of the magnets during hot-press and hot-deformation because the wettability of the RE-rich liquid on the 2:14:1 grains became poor when La was substituted for Nd in the 2:14:1 grains.These results indicate that there is room for further im-provement in both the remanence and coercivity of the Ce-and Ce-La-substituted magnets by intro-ducing additional liquid into the grain boundaries prior to hot-press and hot-deformation.By applying the Nd-Cu infiltration process to the melt-spun ribbons(intermediate infiltration,I-infiltration),both the remanence and coercivity of the Nd-saving(Nd 0.7 Ce 0.3)-Fe-B and(Nd 0.7 Ce 0.225 La 0.075)-Fe-B hot-deformed magnets were successfully improved.
基金financially supported by the National Research Foundation of Korea(No.2015R1A2A2A01002795)the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Trade,Industry,and Energy,Republic of Korea(No.10080382)the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2018R1D1A1B07041358).
文摘A grain boundary diffusion process(GBDP)was adopted to improve magnetic properties of Dy-free highly coercive Nd-Fe-B permanent magnet by coating thin layers of Nd and Cu in grain boundaries.For GBDP of Nd and Cu,Nd and Cu were coated by wet process,e.g.,electrochemical and electroless on Nd-Fe-B magnets,which was fabricated by hot-deformed/die-upset with meltspun specimen.Heat treatment was performed for 20 min at 600℃followed by several different cooling conditions.The cooling conditions after heat treatment were varied to understand distribution and micros tructural effects of Nd and Cu species in grain boundaries.The coercivity increased from 1.565 to 1.637 T in oil cooling rate but remanence decreased,while remanence jumped with little decrease in coercivity in furnace cooling.Micros tructure analyses suggested that the coercivity was closely related to the cooling rate as well as distribution of Nd.The mechanism of coercivity enhancement due to the cooling rate was discussed based on the results presented here and those in the literature.
