Abstract
The reactions and phase changes occurring during sintering of NdFeB permanent magnet alloys were studied by differential thermal analysis and scanning electron microscopy. The powders were produced by hydrogen decrepitation and on heating, hydrogen evolution occurred in two stages: firstly from the matrix phase (∼170 °C) and then from the neodymium-rich phase (350–750 °C). The neodymium-rich phase melted at ∼630 °C and no significant microstructural changes occurred below this temperature. Above 630 °C the neodymium phase is mobile, wetting the matrix grains and leading to their magnetic isolation. Densification occurs by a solution/precipitation mechanism.
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Nasseri Pouryazdi, M.R., Johnson, G.W. & Moulson, A.J. Microstructural development and sintering of NdFeB alloys. J Mater Sci 28, 5237–5239 (1993). https://doi.org/10.1007/BF00570070
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DOI: https://doi.org/10.1007/BF00570070