Microstructural and Hydrogen Absorption Studies on Neodymium-Iron-Boron Materials
Hydrogen decrepitation has been developed into a highly successful industrial process. The hydrogen absorption/desorbtion behaviour of alloys based on Nd15Fe77B8 (Neomax composition) and the stoichiometric phase Nd2Fe14B have been examined so as to relate these effects to the microstructure. Microstructural characterisation was carried out with a variety of techniques with a special emphasis on the detection of boron. Variations in the hardness of the material were investigated as a function of ageing time over a range of temperatures. Microstructural observations on ingots of NdFeB alloys solidified by horizontal and vertical float zoning techniques have allowed the phase distribution, grain size distribution and the nature of the solid-liquid growth interface to be studied and compared with the as-cast microstructure. The nature of hydrogen absorption as observed by DTA is complex but may prove to be a useful phase analysis aid as well as a decrepitation route to produce single crystals from large grained material.
KeywordsDifferential Thermal Analysis Hydrogen Absorption Matrix Phase Hydrogen Pressure Solidification Front
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