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

Durrant, Alec James (2014)
M.Res. thesis, University of Birmingham.

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Abstract

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:M.Res. thesis.
Supervisor(s):Walton, Allan
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:Metallurgy and Materials
Subjects:TA Engineering (General). Civil engineering (General)
Institution:University of Birmingham
ID Code:4919
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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