Martensitic transformations of Fe(N) nanoparticles

γ-Fe(N) nanoparticles (containing 5.9%N, atomic fraction) were prepared by laser induced pyrolysis, and the martensitic transformation characteristics of the nanoparticles was studied. It is found that the martensitic transformation temperature of the nanoparticles is much lower than that of the bulk materials with the same composition. The effect of particle size on the transformation temperature was discussed. It is suggested that the hydrostatic pressure resulting from surface tension of the nanoparticles is responsible for the decrease of the transformation temperature. In order to verify the plastic deformation induced martensitic transformation of the γ-Fe(N) nanoparticles, the pressurization (0.5-4.0 GPa) method was adopted, and the effect of pressurization on the martensitic transformation and microstructures of the particles were also presented.