Sm2Fe17Nx化合物の磁気特性に対するMAの効果

概要

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Mechanical alloying is applied to prepare Sm2Fe17Nx permanent magnet. Starting from elemental powders, the formation of hard magnetic phase of Sm2Fe17Nx by milling in a horizontal ball mill and a successive solid-state reaction was studied. The effect of starting composition of powder on product phase was first investigated. At as milled condition powder was found to consist of α-Fe and Sm-Fe alloy amorphous phases when Sm content is less than 19 at% and consist of α-Fe and SmFe2 phase when Sm content is 26 at%. After heating and nitriding treatments pow-der was found to consist of α-Fe and Sm2Fe17Nx when Sm content is less than 15 at% and consist of α-Fe and SmN when the Sm content is 26 at%. When Sm content was 19 at%, nitrided MA powder consists of mostly Sm2Fe17Nx phase. The effect of milling time was studied for the powder of starting composition of Sm19Fe81. When powder was milled longer than 180ks, almost single phase of Sm2Fe17Nx was formed after nitriding. Coercivity was observed to increase linearly with logarithm of milling time from around 72ks and reached to 1200kA/m after 360ks of milling. This high value of coercivity was cosidered to be obtained by ultra fine grain size of Sm2Fe17Nx produced by ball milling and heat treatment.