Phase-Specific Strain Hardening and Load Partitioning of Cold Rolled Duplex Stainless Steel X2CrNiN23-4

Abstract

Multi-phase materials often times consist of constituents with high contrasts in phase-specific mechanical properties. Here, even after homogeneous plastic deformation phase-specific residual stresses develop that may affect the components behaviour in service. For numerical simulation of phase-specific residual stresses, knowledge of the particular phase-specific strain hardening behaviour is essential. In this study, the strain hardening of ferrite and austenite in cold rolled duplex stainless steel of type X2CrNiN23-4 is investigated. By means of X-ray diffraction, the phase-specific load partitioning and residual stress evolution are analysed for uniaxial load application in three directions within the sheets plane, taking into account the sheet metals phase specific anisotropy. In order to assess the necessity for experimental determination of anisotropic phase specific behaviour, the strain hardening parameters, derived from only one loading direction, are implemented in a mean-field approach for prediction of phase-specific stresses. A simplified simulation approach is applied that only considers macroscopic plastic anisotropy and results are compared to experimental findings. For all investigated loading directions, it was observed that austenite is the high-strength phase. This load partitioning behaviour was confirmed by the evolution of phase-specific residual stresses as a result of uniaxial elasto-plastic loading. With the simplified and fast numerical approach, satisfying results for prediction of anisotropic phase-specific (residual) stresses are obtained.

Neutronographic Analysis of Load Partitioning and Micro Residual Stress Development in Duplex Stainless Steels

“…Regarding diffraction analyses on the load-partitioning behaviour of duplex stainless steels, numerous works have already been published (e.g., [8][9][10][11][12][13]). In particular, investigations of the X2CrNiN23-4 duplex steel with the same nominal phase content of 50:50, which was one of the duplex stainless steels studied within this work, have shown that the austenite phase exhibited significantly higher phase-specific stresses than the ferrite phase and that the load transfer changed depending on the texture orientation [9]. For the X2CrNiMoN25-7-4 duplex stainless steel, it was shown that both phases transferred almost the same phase-specific stress.…”

Stochastic evaluation of stress and strain distributions in duplex steel

“…chapter 6 of Lemaitre and Chaboche [13]) and a linear-exponential hardening law. The models are fit to the results of Simon et al [21]. Again, the texture data of Simon et al [20] is used.…”

“…Fig.1Duplex microstructure: austenite (white) and ferrite phase (multicoloured) with clearly identifiable rolling direction (RD), as determined by electron backscatter diffraction in[21] …”

Neutron and X-ray Diffraction Analysis of Macro and Phase-Specific Micro Residual Stresses in Deep Rolled Duplex Stainless Steels

“…These compressive RS can impede crack initiation and propagation; hence, in most cases they are regarded as beneficial for technical applications [ 7 , 8 , 9 ]. However, for coarse multiphase materials such as duplex stainless steels, the appropriate assessment of RS induced by means of post treatments requires the separation of micro and macro RS, since, in these cases, the material’s load bearing capacity strongly depends on the load partitioning on the phases under applied load and on the phase-specific mechanical behaviour [ 10 , 11 , 12 , 13 , 14 ]. Hence, for the assessment of the stress susceptibility of duplex stainless steels, knowledge on the phase-specific RS induced by the manufacturing or post treatment is essential.…”

“…The crux for RS analysis on duplex stainless steels is that often phase-specific crystallographic textures exist that complicate experimental stress determination as well as the appropriate evaluation of the measured data [ 10 , 11 ].…”