Phase and Elemental Distributions in Alnico Magnetic Materials

TitlePhase and Elemental Distributions in Alnico Magnetic Materials
Publication TypeJournal Article
Year of Publication2013
AuthorsXing Q, Miller MK, Zhou L, Dillon HM, McCallum RW, Anderson IE, Constantinides S, Kramer MJ
Journal TitleIEEE Transactions on Magnetics
Date Published07
Type of ArticleArticle
ISBN Number0018-9464
Accession NumberWOS:000322483200061
Keywordsalloys, co, COERCIVITY, fe, ni, permanent magnets, permanent-magnets, transmission electron microscopy

Insight into microstructural features in commercial alnico alloys is revealed through electron microscopy. Significant differences were found in the chemical make-up of the primary phases and their distributions for the different classes of the alloys. Changes in the Co + Fe : Al + Ni and minor alloying elements shift the matrix phase from an ordered B2 phase found in alnico 5-7 to a L2(1) phase found in alnico 8 and 9. The question whether the FeCo-rich phase has a B2 or body-centered cubic structure remains open. The grain-aligned 5-7 alloy shows a well ordered array of prismatic cells of the FeCo-rich phase that is 20-40 nm in width, 100's nm in length and epitaxial with the B2 matrix. Cu is uniformly distributed in the matrix phase for alnico 5-7 whereas for alnico 8 and 9, pure Cu precipitates locate along the phase boundaries. Ti-rich precipitates and non-spinodal FeCo-rich precipitates are observed.

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