Inversion of Nitrogen Redistribution in Austenitic Steel by Severe Plastic Deformation

Using the Mossbauer spectroscopy and transmission electron microscopy (TEM) methods, the temperature boundary of a strain-induced transformation with the inversion of the direction of nitrogen redistribution is determined in the structure of the FeMn22Cr18N0.83 austenitic steel. Deformation by high pressure torsion in Bridgman anvils below the temperature limit (298 K) leads to an increase in the amount of nitrogen in the interstitial solid solution and deformation above the limit (373 K) leads to a decrease in this value. An increase in the deformation temperature leads to the complete dissolution of the products of cellular decomposition and the formation of submicrocrystalline austenite with secondary nanocrystalline nitrides. Changes in the direction of nitrogen redistribution are explained by the competition between the mechanisms of relaxation of the structure along the paths of dispersion, dissolution of nitrides by dislocation, and decomposition of a solid solution supersaturated with nitrogen.