Microstructural study of as-cast Nd-Fe-B alloys

The primary solidification or iron in Nd-Fe-B alloys is detrimental to the magnetic properties of sintered magnets; around the compositions of the ferromagnetic phi phase (Nd/sub 2/Fe/sub 14/B) some fluctuations of the compositions and/or production processes control this solidification. A microstructural study of as-cast alloys by means of metallography, electron probe, and Mossbauer spectroscopy showed, besides the main phi phase, some amounts of alpha -Fe dendrites and intergranular precipitates of Nd/sub 1.1/Fe/sub 4/B/sub 4/ and of an Nd-rich phase. Following the observations, the boundary separating the primary crystallization field of Fe and phi can be more precisely defined. The optimal composition avoiding iron precipitation can be found.<
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