Isotropic and anisotropic nanocrystalline NdFeB bulk magnets prepared by binder-free high-velocity compaction and hot deformation

NdFeB magnets have a wide range of applications in various electronic devices and driving motors [1]. Anisotropic NdFeB magnets are more attractive for their ability to provide high energy product and high heat resistant [2]. One approach to fabricate anisotropic nanocrystalline NdFeB magnets is hot press and hot-deformation of quenched ribbons [3, 4]. This traditional way, however, will lead to excessive grain growth during the densification and deformation process. Some advances [5,6] focused on the process of spark plasma sintering (SPS) followed by hot deformation, but it is still associated with the grain growth or non-uniform grain structures with coexistence of fine grain zone and coarse grain zone. Furthermore, SPS is high cost and is hardly applied in large scale. High-velocity compaction (HVC) technology was put forward by Höganäs AB Company in 2001 and had a great development in recent years for its high efficiency, low cost and ability to produce high density and good mechanical property bulk materials [7]. Up to know, HVC has been successfully employed for consolidating various kinds of powders, but it has not been reported for NdFeB magnets yet. Here, we report the fabrication of anisotropic nanocrystalline NdFeB magnets by high-velocity compaction and hot deformation.