In this work, we investigated the effect of the treatment duration on the phase formation and dissolution of alloying elements in the process of mechanical alloying (MA) of iron with austenite forming elements in the nitrogen-containing atmosphere. The influence of MA parameters on the phase composition of the alloy showed the first of the alloying elements dissolved in the lattice of iron are nickel, then chrome and manganese. According to experimental data, the dissolution proceeds through the formation of a layered composite. Also the features of the nanocrystalline structure of powder materials Fe-18Cr-8Ni-12Mn-N, synthesized by mechanical alloying are presented. The nanocrystalline structure of these alloys consists of two structural components: grain-crystallites and grain boundary regions. Such type of structure corresponds to the Gleiter model. Dimensions of nanocrystals are in range from 6 to 20 nm.