DIRECT AND REVERSE MARTENSITIC TRANSFORMATION AND FORMATION OF NANOSTRUCTURED STATES DURING SEVERE PLASTIC DEFORMATION OF METASTABLE AUSTENITIC STAINLESS STEEL

The deformed structure features and phase composition changes of austenitic stainless steel after severe plastic deformation by rolling and high pressure torsion in Bridgman's anvils are studied using transmission electron microscopy, X-ray diffraction and magnetization measurement techniques. It is shown that during severe plastic deformation by high pressure torsion not only direct (gamma' -> alpha') but also reverse (alpha' -> gamma) martensitic transformations occur, which is revealed by the changes in the volume content of alpha' - martensite during deformation. Based on the results obtained, the mechanisms of phase transformations and nanostructured states formation are discussed.