Richard Sheridan

High coercivity, anisotropic, heavy rare earth-free Nd-Fe-B by Flash Spark Plasma Sintering

In the drive to reduce the critical Heavy Rare Earth (HRE) content of magnets for green technologies, HRE-free Nd-Fe-B has become an attractive option. HRE is added to Nd-Fe-B to enhance the high temperature performance of the magnets. To produce similar high temperature properties without HRE, a crystallographically textured nanoscale grain structure is ideal; and this conventionally requires expensive “die upset” processing routes. Here, a Flash Spark Plasma Sintering (FSPS) process has been applied to a Dy-free Nd30.0Fe61.8Co5.8Ga0.6Al0.1B0.9 melt spun powder (MQU-F, neo Magnequench). Rapid sinter-forging of a green compact to near theoretical density was achieved during the 10 s process, and therefore represents a quick and efficient means of producing die-upset Nd-Fe-B material. The microstructure of the FSPS samples was investigated by SEM and TEM imaging, and the observations were used to guide the optimisation of the process. The most optimal sample is compared directly to commercially die-upset forged (MQIII-F) material made from the same MQU-F powder. It is shown that the grain size of the FSPS material is halved in comparison to the MQIII-F material, leading to a 14% increase in coercivity (1438 kA m−1) and matched remanence (1.16 T) giving a BHmax of 230 kJ m−3.

Production and Application of HPMS Recycled Bonded Permanent Magnets for a Traction Motor Application

Due to the volatility of the cost and sustainability concerns associated with the rare-earth permanent magnets, alternative product designs using less or no rare-earth contents have, recently, gained popularity. Another method to address this need is to apply a magnet recycling process, such as the novel hydrogen processing of magnetic scrap (HPMS) which can be applied to the end-of-life products such as hard drive disks. Despite the growing research on the background science of different recycling techniques, a practical make, use and evaluation of recycled magnets in a real-life application, is rarely attended. To address this gap, in this paper and for the first time, the viability of the HPMS recycled magnets for use in a permanent magnet traction motor is investigated. On this basis, a detailed description and testing of the recycling process and the magnet production for a customized traction motor design is provided. Furthermore, the behavior of the motor using the final magnet product is analyzed using simulations and prototype testing. Based on the results, the proposed recycled magnets satisfy the overall requirements, while demonstrating similar or better electromagnetic performance compared to the alternative low-cost ferrite magnets.