Preparation of an α″-Fe16N2 Magnet via a Ball Milling and Shock Compaction Approach†

α″-Fe16N2 has been suggested as a promising candidate for future rare-earth-free magnets. In this paper, a unique technical route including a ball milling approach and shock compaction is experimentally demonstrated as a promising way to produce an α″-Fe16N2 magnet. Firstly, α″-Fe16N2 powder is prepared by ball milling, in which ammonium nitrate (NH4NO3) is adopted as a solid nitrogen source. The volume ratio of the α″-Fe16N2 phase reaches 70% after 60 h of milling with a ball mill rotation speed of 600 rpm in planetary mode. Its saturation magnetization (Ms) is 210 emu g–1 and the coercivity is 854 Oe at room temperature. After ball milling, shock compaction is used to compact the milled powder sample into a bulk magnet. Its magnetic properties and crystalline structure are characterized. Overall, the ball milling-based approach can be used to prepare α″-Fe16N2 magnets at an industrial production level.