Shock compression response of magnetic nanocomposite powders

The shock compression response of magnetic Pr₂Fe ₁₄B/α-Fe nanocomposite powders, pressed at different packing densities, was studied in the range of 11-23 GPa shock pressure, using a single-stage gas gun. Bulk compacts (97.5-99% dense) recovered in the form of 12 mm diameter by 4 mm thick disks, were analyzed to determine the structural changes occurring within the particles and at particle boundaries. Scanning electron microscopy observations revealed presence of laminar morphology and strong inter-particle bonding. X-ray diffraction and transmission electron microscopy analysis revealed the retention of nanoscale structure and localized grain refinement. Shear bands were observed and thought to be responsible for the grain refinement. The compact of powders pressed at the intermediate packing density (∼76% dense) showed the best densification characteristics, correspondingly, the best magnetic properties with strongest exchange coupling between hard and soft phases.