This study examines the patterns of macroscopic inhomogeneity and localization of plastic flow in Fe-Cr-Ni polycrystals subjected to uniaxial tension. By varying the test temperature, the deformation curves can be altered, allowing us to explore the behavior of the material under different conditions. The stress-strain diagrams obtained from the samples reveal the areas of elastic deformation, plastic flow, and fracture. To experimentally study plastic flow, we used speckle photography to accurately reconstruct the displacement vector fields and calculate the components of the plastic distortion tensor. The results showed that plastic flow is localized at all stages of the process for test temperatures of+65, +24, and -60 °C. The forms oflocalization are entirely determined by the dependence of the strain hardening coefficient on the deformation during the relevant stage of the process. An analysis of the spatial distributions of local shifts and local rotations was conducted. We observed spatially periodic structures that can be interpreted as autowave processes and explained in terms of the concept of self-organization of the plastic flow process.

The paper considers the regularities of macroscopic inhomogeneity of plastic flow during uniaxial tension of flat samples of Fe-Cr-Ni 2 mm thick. Their tension axis was oriented along the rolling direction. The average grain size was 12.5 ± 3 mm. The plastic flow curves of the alloy had long stages of linear strain hardening over the entire test temperature range 180 K < T < 297 K. For the experimental study of plastic deformation, we used the method of accurately reconstructing the fields of displacement vectors and calculating the components of the plastic distortion tensor using speckle photography with increments of the total strain between exposures 0.001. The field of displacement vectors as a whole over the sample during loading is inhomogeneous both in the directions of the displacement vectors and in values; in some areas, the displacement vectors nonmonotonically change directions relative to the tension axis. It has been established that in the test temperature range 180 K < T < 297 K, plastic flow is localized at all stages of the process. The appearance of the a′-martensite phase during the deformation of the alloy under study leads to a change in the mechanical characteristics, the work hardening coefficient, and the deformation localization parameters. The maps of deformation structures are analyzed in the form of spatial distributions of the components of the plastic distortion tensor: local elongations, narrowings, shifts and rotations. The non-linear nature of the change in the coefficient of transverse deformation from the level of acting stresses is established. The general form and quantitative parameters of the evolution of the components of the plastic distortion tensor indicate the connection of this process with the self-organization of a defective subsystem in a deformable medium.

Stress-strain behavior of austenitic stainless steel grade AISI 304 was investigated by means of uniaxial tensile tests and magneto-phase analysis. The test materials were strained in tension within the temperature range of-100 ≤ T ≤ +100 °C. According to the results, intensive strain hardening occurs in austenitic stainless steel when strain-induced α’- martensite is present in the material, and stress-strain behavior is associated with the increase yield strength and tensile strength with decreasing temperature. The analysis of the hardening kinetics reveals that kinetics are affected by the temperature and by the amount of α’- martensite content.