Abstract
The crystal structure of the α" phase in tempered Fe-N martensite was refined by means of single-crystal electron diffraction intensity analysis. Electron diffraction intensities recorded on imaging plates were compared with the intensities calculated to take account of dynamical. The crystal structure of α" belongs to the space group I4/mmm, and the lattice parameters are a = 0.572 and c = 0.631 nm. The positional parameters x for Fe(8h) and z for Fe(4e) are x = 0.220 and z = 0.303. On the basis of these structural data, electronic band structure calculations using full-potential LAPW method were performed for the Fe16N2. The average magnetic moment per Fe atom is about 2.2 μB, which is nearly equal to that of α-Fe. In high-resolution electron microscope images, α" regions in which the N concentration was less than that of Fe16N2 were observed locally between the Fe16N2 precipitates and the tempered matrix. The magnetic structure of the local non-stoichiometric α" phase is discussed in relation to the band structure.
