Preparation of Isotropic and Anisotropic Nanocrystalline NdFeB Magnets by High-Velocity Compaction and Hot Deformation

NdFeB powders are consolidated into nanocrystalline bulk magnets by a near-net-shape process of high-velocity compaction (HVC) at room temperature with no binder employed. The magnets prepared under various conditions, including impact energy, filling weight, mold dimension, and plasticity and size of the starting powders, were investigated. The results showed that the density of as-compacted NdFeB magnets increased with the increasing impact energy and decreasing filling weight. The as-compacted magnets with relatively high density can inherit the coercivity and microstructure of the starting powders. The small flake powders with good plasticity and/or large mold diameter are beneficial to obtain high density. The relative green densities for the samples with low-Nd composition and high-Nd composition reach 92% and 87.5%, respectively. Using the HVCed magnet as the precursor, the anisotropic NdFeB magnets with enhanced magnetic properties have been prepared by hot deformation. This paper provides an alternative technique for preparing nanocrystalline NdFeB magnets.