Effects of Grain Orientation on Stress State near Grain Boundary of Austenitic Stainless Steel Bicrystals

Abstract

e stress state at the crack tip of structural components in nuclear power plants used in the SCC quantitative prediction models is based on the assumption that the polycrystalline material is isotropic and homogeneous at present. However, the crystals in polycrystalline materials are anisotropic with different orientations, which would induce a nonuniform stress to cause the initiation and propagation of SCC. By using a finite element method, the elastic responses of anisotropic behaviors of austenitic stainless steel bicrystals are studied. e results indicate that the stress distribution near GBs depends strongly on the crystal orientation. A larger Mises stress concentration exists on the GB with larger stiffness along the load direction. e Mises stress difference is higher in the bicrystal with bigger elastic modulus difference of two neighboring grains along the tensile axis. In the bicrystal with GB perpendicular to the tensile axis, the grain orientation has little effects on the Mises stress far from the GB in both grains. e strain inconsistency in bicrystals is affected by the mismatch of two neighboring grains. e larger the elastic modulus differences between two neighboring grains caused by misorientation, the larger the strain inconsistency in the bicrystal.

Modeling the Hydrogen Redistribution at the Grain Boundary of Misoriented Bicrystals in Austenite Stainless Steel

“…[100] Considering the relationship between the [100], [110], and [111] orientations and the stretching axis, three types of crystals with different orientations were modeled [28], as shown in Table 1 As shown in Figure 3, to ensure the material coordinate o-x y z coincide with the global coordinate o-xyz, the material coordinate o-x y z should be rotated. The rotation matrices of material coordinate o-x y z with respect to the global coordinate o-xyz are [37],…”

“…Due to elastic anisotropy, the anisotropic elastic behavior of microstructure at grain boundaries can produce local stress concentrations [27] and strong hydrostatic stress gradients under mechanical loading even without notch or crack [28,29]. In the present work, the hydrogen diffusion at the grain boundary was investigated by a proposed hydrogen diffusion model, which is based on the elastic response of the anisotropic behavior of crystals.…”

Effects of Crystal Orientation and Grain Boundary Inclination on Stress Distribution in Bicrystal Interface of Austenite Stainless Steel 316L

“…Despite the method with FIB enables researches to investigate the IGSCC in single GBs [24][25][26][27], it is difficult to manufacture specific single grain boundaries with respect to the irregularity of GBs and accurately measure the stress and strain distribution nearby GBs. us, the elastic response of anisotropic behaviors of the austenitic stainless steel crystal was presented by a constitutive model, and the effects of crystal orientation on the stress state near the GB were studied by the finite element method [28]. In this paper, a three-dimensional anisotropic finite element analysis, which focuses on the bicrystal with a symmetric tilt GB, is performed to obtain how crystal orientation and grain boundary inclination affect the stress state nearby the GB of the bicrystal.…”

Compilation and Application of UMAT for Mechanical Properties of Heterogeneous Metal Welded Joints in Nuclear Power Materials

“…Due to the particularity of the welding process, the mechanical properties of the welded joints are not uniform and the metallographic changes of the materials, the discontinuity of the structure, the variation of the mechanical field, and the evaluation of the service life as well as the safety of the structure have always been the focus of scholars and engineers. Yang et al [7,8] investigated the effect of the elastic response of austenitic behavior of austenitic stainless steel, the orientation of crystal orientation, and the grain boundary (GB) dip angle under constant displacement by means of numerical simulation. e results showed that the larger the difference in the orientation of the twin crystal, the greater the strain inconsistency of the twin crystal.…”