Studying Deformation Behaviors in Austenitic Stainless Steels within a Temperature Range of 143 K < T < 420 K

Abstract

This work deals with studying staging and macroscopic strain localization in austenitic stainless steel 12Kh18N9T within a temperature range of 143 K &lt; T &lt; 420 K. The visualization and evolution of macroscopic localized plastic deformation bands at different stages of work hardening were carried out by the method of the double-exposure speckle photography (DESP), which allows registering displacement fields with a high accuracy by tracing changes on the surface of the material under study and then comparing the specklograms recorded during uniaxial tension. The shape of the tensile curves σ(ε) undergoes a significant change with a decreasing temperature due to the γ-α'-phase transformation induced by plastic deformation. The processing of the deformation curves of the steel samples made it possible to distinguish the following stages of strain hardening, i.e. the stage of linear hardening and jerky flow stage. A comparative analysis of the design diagrams (with the introduction of additional parameters of the Ludwigson equation) and experimental diagrams of tension of steel 12Kh18N9T for different temperatures is carried out. The analysis of local strains distributions showed that at the stage of linear work hardening, a mobile system of plastic strain localization centers is observed. The temperature dependence of the parameters of plastic deformation localization at the stages of linear work hardening has been established. Unlike the linear hardening, the jerky flow possesses the propagation of single plastic strain fronts that occur one after another through the sample due to the γ-α' phase transition and the Portevin-Le Chatelier effect. It was found that at the jerky flow stage, which is the final stage before the destruction of the sample, the centers of deformation localization do not merge, leading to the neck formation.

Temperature Effect on Deformation Response in Austenitic Stainless Steel

“…Martensitic mechanisms are effective mechanisms for increasing the strength properties of austenitic steels, which depend on the thermodynamic stability of austenite and deformation conditions (value, temperature). The study of the kinetics of these processes at different temperatures made it possible to establish the patterns of macroscopic localization of plastic deformation [15][16][17][18].…”

“…The PLC effect in a metastable steel was studied via uniaxial tension tests at temperatures from 293 to 413 K and at strain rates from 0.0001 to 0.1 с -1 . The stress-strain curves were completed with the measured thermal fields and acoustic emission data, which enabled one to distinguish various local characteristics of plastic flow and to evaluate the individual contributions from the different microscopic mechanisms involved in plastic strain [15][16][17][18].…”

Analysis of Unstable Plastic Flow in the Porous 316L Samples Manufactured with a Laser 3D Printer

“…Austenitic steel 316L belongs to the type of room-temperature stable austenitic steels [18]. The formation of deformation martensite in 316L conventional austenitic steel, which leads to a decrease in plastic properties, was observed under low-temperature deformation or at high percentages of deformation (≥50%) at room temperature [19][20][21]. As for the DSA process associated with PLC effect in 316L conventional steel, the DSA process was observed at high temperature deformation.…”