Effect of martensitic phase transformation on the behavior of 304 austenitic stainless steel under tension

Abstract

The present work integrates in-situ neutron diffraction, electron backscatter diffraction and crystal plasticity modeling to investigate the effect of martensitic phase transformation on the behavior of 304 stainless steel under uniaxial tension. The macroscopic stress strain response, evolution of the martensitic phase fraction, texture evolution of each individual phase, and internal elastic strains were measured at room temperature and at 75°C. Because no martensitic transformation was observed at 75°C, the experimental results at 75°C were used as a reference to quantify the effect of formed martensitic phase on the behavior of 304 stainless steel at room temperature. A crystallographic phase transformation model was implemented into an elasticviscoplastic self-consistent framework. The phase transformation model captured the macroscopic stress strain response, plus the texture and volume fraction evolution of austenite and martensite. The model also predicts the internal elastic strain evolution with loading in the austenite, but not in the martensite. The results of this work highlight the mechanisms that control phase transformation and the sensitivity of modeling results to them, and point out to critical elements that still need to be incorporated into crystallographic phase transformation models to accurately describe the internal strain evolution during phase transformation.

Assessment of Martensitic Transformation Paths Based on Transformation Potential Calculations

“…The ϵ martensite subsequently transforms to α ′ martensite, as evidenced by the higher α ′ martensite fraction than ϵ martensite fraction. This result may also explain the increases in Goss and cube orientations seen by others …”

“…However, a series of papers studying an SAE 304 stainless steel with electron backscatter diffraction (EBSD) showed minimal martensite in cube and Goss oriented grains . Orientation distribution functions (ODFs) of other austenitic steels have generally shown an increase in cube and Goss oriented grains after uniaxial deformation, also indicating that these orientations were not transforming . This increase in Goss and cube orientations is in contradiction to expected transformation potential results for a γ → α ’ transformation, such as made previously by the authors, which also predicted that grains with crystal axes aligned with the cube and Goss orientations would transform first.…”

Effect of Nitrogen on Deformation-Induced Martensitic Transformation in an Austenitic 301 Stainless Steels

“…This failure in early stage of plastic deformation also can be observed as resulted in specimen A when DIMT process occurs so fast that work-hardening rate increases rapidly. Therefore it is important to control the optimized stability of austenite in order to obtain high strength along with elongation in metastable austenitic alloys [4,12]. Figure 4 shows true stress-strain curves of all specimens.…”

“…DIMT in austenitic stainless steels has been observed to proceed either directly from γ-austenite to α' martensite (γ → α') [1,2] or via ε martensite (γ → ε → α') depending on alloy composition and crystallographic orientation [2][3][4][5]. Generally, DIMT phenomenon has been analyzed in terms of either transformation kinetics or stress-strain response [4,[6][7][8][9][10][11][12][13][14][15][16][17]. The transformation kinetics of DIMT prescribes the relation between the volume fraction of transformed martensite and plastic strain, while the change in deformation behavior due to DIMT has also been analyzed in relation to the variation of stress-strain curve and mechanical properties [1,10,13,18].…”

“…In order to obtain both high strength and ductility in TRIP steels, mechanisms of the formation of retained austenite, transformation behavior of retained austenite and the deformation behavior related to transformation should be thoroughly investigated [4,11,12]. In terms of DIMT kinetics, the stability of the retained austenite should not be either too high or too low for achieving optimized combination of strength and elongation.…”