High resolution microscopy of NdFeB magnets produced from flash spark plasma sintering (FSPS) and the hydrogen ductilisation process (HyDP)

Zhou, Wei (2019). High resolution microscopy of NdFeB magnets produced from flash spark plasma sintering (FSPS) and the hydrogen ductilisation process (HyDP). University of Birmingham. Ph.D.

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Abstract

In recent years, the increasing demand for rare earth magnets for use in motors and machines has led to the need for more efficient use of NdFeB materials. Novel processing techniques have been developed to produce NdFeB materials with excellent magnetic properties without the need for heavy rare earth elements. Two specific novel processes including the Flash Spark Plasma Sintering (FSPS) process and the Hydrogen Ductilisation Process (HyDP) were studied in this project with the focus on the use of microstructural analysis and magnetic measurements to fully understand the mechanisms, hence develop and optimise the processing conditions for production of fully dense anisotropic magnets. The most optimal FSPS sample demonstrates a uniform, fine-grained structure with a high degree of crystallographic alignment, leading to a high coercivity (1438 kA m\(^−\)\(^1\)) and remanence (1.16 T) giving a BH\(_m\)\(_a\)\(_x\) of 230 kJ m\(^−\)\(^3\). While with appropriate s-HDDR and compression conditions, the HyDPed sample exhibits a typical s-HDDR microstructure with a submicron grain size. It is shown in the work that the disproportionated sample shows an enhanced ductility and thus can be shaped at room temperature, and a useful degree of anisotropy is produced within the HyDPed sample during the compression.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):