Formation of fully austenitic ultrafine-grained high strength state in metastable Cr–Ni–Ti stainless steel by severe plastic deformation

The present research establishes a possibility of producing nano- and submicrocrystalline structure in fully austenitic state of the metastable Cr–Ni–Ti steel after high pressure torsion (HPT) by raising the temperature of severe plastic deformation above the treshold value for strain-induced martensite transformation, and at room temperature by reducing the temperature of strain-induced martensite transformation with the grain size decreases during step-by-step decreasing HPT temperature. •Decreasing of the grain size reduces the temperature of martensite transformation.•HPT with step-by-step decreasing temperature produces an austenite nanostructure.•Fully austenite state is achieved by reducing the martensite threshold value.•The microstructure was refined by HPT down to a mean grain size of 60–120nm.•HPT increases the strength of Cr–Ni–Ti steel by 3–6 times with a loss in ductility.