Rare earth magnets are the strongest type of permanent magnets and are integral to the high tech industry, particularly in clean energies, such as electric vehicle motors and wind turbine generators. However, the cost of rare earth materials and the imbalance in supply and demand still remain big problems to solve for permanent magnet related industries. Thus, a magnet with abundant elements and moderate magnetic performance is required to replace rare-earth magnets. Recently, a”-Fe16N2 has attracted considerable attention as a promising candidate for next-generation non-rare-earth permanent magnets due to its gigantic magnetization (3.23 T). Also, metastable a”-Fe16N2 exhibits high tetragonality (c/a = 1.1) by interstitial introduction of N atoms, leading to a high magnetocrystalline anisotropy constant (K1 = 1.0MJ/m3). In addition, Fe has a large amount of reserves on the Earth compared to other magnetic materials, leading to low cost of raw materials and manufacturing for industrial production. In this paper, we review the synthetic methods of metastable a”-Fe16N2 with film, powder and bulk form and discuss the approaches to enhance magnetocrystalline anisotropy of a”-Fe16N2. Future research prospects are also offered with patent trends observed thus far.

The suitable tools for CGI material has not been developed yet because of high hardness, high toughness and very low machininability compared to the grey cast iron. And the tool life has been decreased as the contents of Ti in CGI material. From this research, we were able to do the high speed machining by using high toughness silicon nitride ceramic tools. The silicon nitride ceramic tool grade was specially designed and prepared with microstructure of elongated grains with higher aspect ratio (c/a) than conventional one.