Nanostructured Fe-18Cr-11Mn-5Mo-xN alloys were prepared by attrition milling of elemental powders under N-2 atmosphere for different times. It was found that the amount of nitrogen present in the powder mixture increased up to 1.6 wt% after 192 h. As-milled powders were encapsulated in quartz tubes and heat treated at 1173 and 1473 K to promote austenisation. Different phases were identified posterior to crystallization namely, ferrite, austenite and Cr2N, which occurred in different amounts depending on the nitrogen content and the heat-treatment temperature. No nitrogen desorption was perceptible after the crystallization annealing treatment. The results showed that it is feasible to obtain a fully austenitic structure by controlling the processing parameters.