Abstract: Effects of strain-induced martensitic transformation during cold rolling and aging process on mechanical properties of the 1RK91 stainless steel were studied by means of optical microscope (OM), X-ray diffraction (XRD), field emission scanning electron microscope (SEM), Vickers hardness tester and universal material testing machine. The results show that the strain-induced martensite transformation occurs during cold rolling of the 1RK91 stainless steel. The nucleation of strain-induced martensite depends on the proliferation and movement of dislocations during cold rolling and is affected by the deformation temperature. The tensile strength and dislocation density of the material increase with the increase of cold rolling deformation, and the tensile strength after solid solution and 75% cold rolling are 903 MPa and 1195 MPa, respectively, the dislocation densities are 5.75×10¹⁰ cm^-2 and 8.84×10¹⁰ cm^-2, respectively, and the calculated cold-working strengthening coefficient of the steel is 3.89 MPa/%. Under conventional aging, the peak hardness of solid solution treated and 75% deformed steel are 499 HV0.2 and 610 HV0.2, respectively, and after graded aging, the peak hardness are 513 HV0.2 and 639 HV0.2, respectively. With the increase of deformation, the peak hardness of the conventional aged material increases, and the temperature to reach the peak hardness decreases. After graded aging, the material has higher peak hardness and better anti-over-aging ability on the whole.

Key words: 1RK91 stainless steel, cold rolling, strain-induced martensite, aging process, hardness