The effect of microstructure and composition on HDDR processing of scrap magnets

Durrant, Alec James (2014). The effect of microstructure and composition on HDDR processing of scrap magnets. University of Birmingham. M.Res.

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Due to increasing pressure on the supply of rare earth metals there is a growing need to develop recycling strategies for rare earth containing materials. The aim of this investigation was to use the Hydrogenation Disproportionation Desorption Recombination (HDDR) processing technique to recycle sintered magnets and cast rare earth alloys based upon neodymium iron boron (NdFeB). The study investigated the impact of microstructure and composition on the HDDR processing conditions and resultant magnetic properties of the NDFeB powders. Heat treatment techniques were used to alter the grain size of sintered magnets to simulate a variety of NdFeB feedstock for HDDR recycling. To investigate the effect of the composition on HDDR recycling process a comparison between two cast alloys with varying Nd content was undertaken. The HDDR powder created by the recycling process was assessed using a vibrating sample magnetometer (VSM). Microstructural analysis was carried out using optical and backscattered scanning electron microscopy.

This study demonstrated that it is possible to develop significant anisotropy using the HDDR process on sintered NdFeB-type magnets. However the same processing conditions could not be applied to materials with larger grain sizes or cast materials. This study also explains the effect heat treatments can have on the development of soft magnetic phases.

Type of Work: Thesis (Masters by Research > M.Res.)
Award Type: Masters by Research > M.Res.
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Metallurgy and Materials
Funders: None/not applicable
Subjects: T Technology > TA Engineering (General). Civil engineering (General)


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