Comparison of self-consistent and crystal plasticity FE approaches for modelling the high-temperature deformation of 316H austenitic stainless steel

Abstract

The present article examines the predictive capabilities of a crystal plasticity model for inelastic deformation which captures the evolution of dislocation structure, precipitates and solute atom distributions at the microscale, recently developed by Hu and Cocks [1,2]. The model is implemented within a self-consistent framework and a crystal plasticity finite element (CPFE) scheme. Through direct comparison between the two CP schemes and with an extensive material database for Type 316H stainless steel, the different types of information and the degree to which the models are consistent with experimental observations are assessed. The study demonstrates an agreement between the SCM and the CPFE schemes, providing confidence in the micromechanical deformation model employed. The multi-scale approach also allows the effects of micro-scale deformation processes, related to dislocation-obstacle interactions, on the global deformation response to be captured. Modelling results from this study and their comparison to experimental observations show that deformation of polycrystalline materials, such as 316H stainless steel, is controlled by the evolution of microstructural state of the material and the redistribution of stress between individual grains. The study suggests that the SCM is a feasible tool to simulate and explain the deformation behaviour of complex alloys under industrially-relevant thermo-mechanical operating histories. The CPFE framework captures the effects of the variation in grain geometry and provides more detailed information about the variation of stress and strain within the individual grains, particularly their distribution near grain boundaries and triple pointswhich are important to understand in the context of damage development and failure. The SCM predicts a -stiffer‖, more creep-resistant response than a CPFE model for a given set of material parameters due to the more highly-constrained deformation modes allowed in the model. As a result, material parameters calibrated using one modelling approach are not necessarily suitable for use in another approachalthough parameters obtained when fitting the different models should not vary significantly.

Self-consistent modelling of cyclic loading and relaxation in austenitic 316H stainless steel

“…The response of the individual anisotropic grains is modelled through crystal plasticity (CP) theory, which is treated within a small-deformation framework, since the SCM developed by Hu and Cocks [2] is built within a framework where lattice rotations are ignored. Petkov et al [47] have compared predictions using the SCM model with full 3-D large deformation CPFE simulations and demonstrated that for the range of problems of interest here (macroscopic strains up to 5%) the current small deformation assumption provides an accurate description of the macroscopic response. The plastic strain rate in each crystal can be determined via the CP model by summation of the slip rates on individual slip systems within the crystal.…”

Scratching the Surface: Elastic Rotations Beneath Nanoscratch and Nanoindentation Tests

“…The symmetry plane was fixed from translation in the normal direction, x 2 = 0, the nodes on the top surface were traction free, while the remaining four surfaces of the cube were fixed. Elastic anisotropy was used with the following elastic constants for copper: Further details on the UMAT can be found in [60,63,64,65,62,66]. Simulations provide direct comparison with the EF scratch test.…”

Continuous Grain Size Gradients in Austenitic Incoloy 800H: Design, Processing, and Characterization

“…An integrated multi-scale model incorporating model grain geometries and orientations and crystal plasticity was recently demonstrated for creep in 316H stainless steel [51]. Applying this method to model gradient microstructures may shed light on the relation between grain size gradients and creep damage, see [52] for an example.…”