Dirba, Imants ; Pattur, Prudhvi ; Soldatov, Ivan ; Adabifiroozjaei, Esmaeil ; Molina-Luna, Leopoldo ; Gutfleisch, Oliver (2022)
Grain Boundary Infiltration in Hddr Processed Nd2fe14b Magnets.
In: SSRN Electronic Journal, 2022
doi: 10.2139/ssrn.4100224
Article, Bibliographie

Abstract

We investigate the grain boundary infiltration process of various low melting eutectic alloys for the coercivity enhancement of hydrogenation disproportionation desorption recombination (HDDR) processed Nd-Fe-B powders. Nd-based as well as heavy rare earth (Tb) and light rare earth (La, Ce) containing alloys were systematically studied: Nd 70 Cu 30 , Nd 90 Al 10 , Nd 80 Ga 15 Cu 5 , Nd 62 Fe 14 Ga 20 Cu 4 , Nd 60 Tb 10 Cu 30 , La 71 Cu 29 and Ce 72 Cu 28 . Moreover, the Fe content in the quaternary Nd-Fe-Ga-Cu system was varied to investigate the effect of grain boundary phase magnetism on the resultant coercivity.The largest coercivity enhancement, from 0.42 T in the as-HDDR powder to 1.88 T after infiltration was observed in the case of ternary Nd 80 Ga 15 Cu 5 composition. Furthermore, it also shows the best temperature stability with the infiltrated sample still exhibiting a coercivity of 0.58 T at 200°C. Infiltration of light rare earth (La, Ce) based alloy did not increase coercivities due to poor wetting at the grain boundaries. Adding Fe to the grain boundary alloys was shown to enhance magnetization up to a certain extent without significant loss in coercivity. These findings demonstrate the effectiveness of grain boundary infiltration in HDDR-processed magnets without using heavy rare earths. The infiltration with non-magnetic material strongly decreases theintergranular interaction, reflected in a different magnetic domain evolution during the magnetization reversal process.

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