The phase transformations and nanostructure formation in metastable stainless steel Khl8N8 are studied during nitriding and subsequent severe cold plastic deformation by high-pressure torsion in Bridgman anvils. Ion-plasma nitriding of the steel leads to the nitrogen saturation of austenite, CrN nitride formation, and the destabilization of the structure with respect to the gamma-alpha. transformation. Subsequent deformation is accompanied by the reverse alpha-gamma phase transformation, the dissolution of nitrides, and the formation of nitrogen-supersaturated solid solutions and secondary nanonitrides. These fine particles restrict the grain growth in the matrix and stabilize the nanostructure formed.
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