Process optimization to produce anisotropic NdFeB permanent magnets from recycled powder via powder extrusion

In this study, process parameters are presented on how to optimize the novel process for producing anisotropic NdFeB permanent magnets from recycled materials using powder extrusion moulding (PEM). The process is based on the recycling of end-of-life (Eol) magnets that have been processed into powder by the Hydrogen Processing of Magnetic Scrap (HPMS) process. In this study, the influence of melt temperature on the alignment behaviour of magnetic particles during in situ alignment using the PEM process is investigated. This process enabled the fabrication of sintered, anisotropic NdFeB permanent magnets with a high degree of alignment, as indicated by a B_r/J_s ratio of 0.96. Moreover, the challenges associated with the production of anisotropic NdFeB permanent magnets with PEM are delineated in this study. The primary focus of this study is on the carbon and oxygen content. The study found that sintered magnets with a carbon content of approximately 0.045 wt% could be produced using the PEM process. The oxygen content, however, exhibited a variation depending on the initial material used. Nonetheless, the oxygen content increased by approximately 0.4 wt% from the HPMS powder to the sintered part.