Deformation-induced transformations in nitride layers formed in bcc iron

The behavior of nitrides (Fe4N and TiN) was analyzed in layers formed by the ion deposition on the bcc iron surface during intensive cold (300 K) compression-shear deformation. The study revealed the scheme and the mechanism of deformation-induced phase transitions of the nitrides, which were followed by the formation of nanocrystalline nitrogen-supersaturated solid solutions and secondary Fe16N2 and Fe4N nitrides. The dissolution of the Fe4N nitride in the bcc iron matrix was taken as the example to show that the concentration of the less mobile element (iron) increased regularly in the newly formed nitrides. The main distinctions between the structure of the mechanically synthesized nitrous solid solution and that of the metallurgical nitrous martensite were established. It was shown that the dispersion of the nitride phases in the layers precipitating in bcc iron determined a fast kinetics of the cold mechanical synthesis (MS) and provided the possibility to produce nanocrystalline nitrogen-supersaturated solid solutions of iron.