Tensile Deformation Behavior of Duplex Stainless Steel Studied by In-Situ Time-of-Flight Neutron Diffraction

Abstract

For a duplex alloy being subjected to deformation, the different mechanical behaviors of its constituent phases may lead to a nonuniform partition of stresses between phases. In addition, the grain-orientation-dependent elastic/plastic anisotropy in each phase may cause grain-tograin interactions, which further modify the microscopic load partitioning between phases. In the current work, neutron diffraction experiments on the spectrometer for materials research at temperature and stress (SMARTS) were performed on an austenite-ferrite stainless steel for tracing the evolution of various microstresses during tensile loading, with particular emphasis on the load sharing among grains with different crystallographic orientations. The anisotropic elastic/plastic properties of the duplex steel were simulated using a visco-plastic self-consistent (VPSC) model that can predict the phase stress and the grain-orientation-dependent stress. Material parameters used for describing the constitutive laws of each phase were determined from the measured lattice strain distributions for different diffraction {hkl} planes as well as the laboratorial macroscopic stress-strain curve of the duplex steel. The present investigations provide in-depth understanding of the anisotropic micromechanical behavior of the duplex steel during tensile deformation.

In Situ Observation of the Deformation and Fracture Behaviors of Long-Term Thermally Aged Cast Duplex Stainless Steels

“…APT has been widely used to characterize the spinodal decomposition in Fe-Cr alloys and ferrite in CDSS, and the average size of the Cr-enriched and Cr-depleted domains was estimated to be approximately 7 nm for CDSS that was thermally aged for 20,000 h [18]. The Young's modulus and shear modulus of pure Cr are higher than those of pure iron, and in the alloys they increase with increasing Cr content [19]. The different moduli between Cr-enriched and Cr-depleted domains caused deformation incompatibility on the nanometer scale, forming many regions with different orientations, as shown in Figure 6c,d.…”

“…Thermal aging causes severe hardening in ferrite [3,7,18], leading to deformation heterogeneity between ferrite and austenite in the aged CDSS. As a result, the stress and strain repartition of the two phases may play an important role in the fracture process [19]. The hardened ferrite and stress phase boundary may act as the site of crack initiation.…”

Principles and Technical Parameters of High‐Pressure Torsion

“…Second, the γand α-phases exhibit similar behavior in the elastoplastic regime, resulting in relatively weak interphase interactions [54], and both phases deform simultaneously [55,56]. However, the following discussion suggests that these results are universal.…”

Microstructural Evolution of an Al-Alloyed Duplex Stainless Steel During Tensile Deformation Between 77 K and 473 K (−196 °C and 200 °C)

“…[7,[14][15][16] Inhomogeneities during the deformation of duplex steels originate not only from the differences in the strength and the strain-hardening behavior of the constituents but also from a non-uniform partitioning of the stress. [17,18] It has been suggested that the phase boundaries play a key role in creating local stress gradients during the deformation of duplex steels. [19,20] The plastic deformation of ferrite grains has been discussed in view of slip induced by the dislocation accumulation in the neighboring austenite grains.…”