The effect of 1 MeV N+ irradiation on the microstructure of Fe and Ti specimens was investigated. The Fe and Ti specimens were implanted such that the N peak concentration (30 at.% in Fe, 45 at.% in Ti), was below the concentration of N in ε-Fe2N and δ-TiN, respectively. X-ray diffraction phase analysis showed that ε-Fe2N and δ-TiN had formed. X-ray diffraction stress analysis indicated that the residual stress in the Fe and Ti matrices was negligible after implantation. This suggests that the volume misfit due to nitride formation had been accommodated by plastic deformation. Indeed, surface profilometry of implanted Fe showed that a volume increase of the specimen had occurred which was compatible with the formation of unstrained nitride .