Intergranular strain evolution near fatigue crack tips in polycrystalline metals

Insights from the Lattice-Strain Evolution on Deformation Mechanisms in Metallic-Glass-Matrix Composites

“…The crystalline phase can be assigned with a slip-based crystal plasticity model, [25,26] which describes the Schmid law, slip anisotropy, and hardening behavior. The constitutive parameters include elastic constants C 11 , C 12 , and C 44 ; the critical resolved shear stress s 0 ; and those describing strain-rate dependence and hardening behavior.…”

“…Here, we adopt a uniaxial specimen in Figure 2(a) with 7,986 cubes. [25] Half of these cubes belong to the MG matrix, while the other half are of the crystalline phase, as shown in Figure 2(b). This configuration is close to the experimental condition, where the crystalline phases have a volume percentage of~50 pct in the MGMC specimens.…”

“…From the micromechanics standpoint, the lattice strain relies on the intergranular interactions of inhomogeneous deformation fields in neighboring grains, which is also called Type-II strains. [25] In diffraction analysis, the lattice strain in the hhkli direction, e hkl , is calculated from the interplanar spacing (d hkl ), based on the change of values d hkl before and after deformation, which can be measured from the {hkl} peak shift in the diffraction pattern. In elastic deformation, the evolution and anisotropy of e hkl are determined by the elastic anisotropy and texture of materials, while in plastic deformation, they are mainly contributed by plastic slips and intergranular interactions among neighboring grains.…”

“…The deviation of the measured e hkl from the extrapolated curve of the measured elastic-elastic portion is denoted as intergranular strains. [25,26] In the reported diffraction works, Ott et al [23] studied the elastic strain evolution of particle-reinforced MGMCs in single crystal direction using the synchrotron X-ray diffraction and finite element modeling (FEM) during compressive loading. Their simulations are based on continuum Mises plasticity without any reference to the plastic anisotropy in the inclusions, and also there is no reference to the strain localization in the matrix.…”

The effect of prior deformation on subsequent microplasticity and damage evolution in an austenitic stainless steel at elevated temperature

“…Full field polycrystal models have been formulated using fast Fourier transform techniques for materials with periodic microstructure, which have been employed for lattice strain predictions (see, e.g., [25,26]). More commonly, finite element (FE) methods have been used to complement in-situ ND observations, with either simplified grain topology [7,8,12,20,22] or complex/realistic geometries [19,[27][28][29][30] taken into account. As shown in a recent work [29], an accurate prediction of lattice strain evolution can be achieved using a microstructure-based FE model for austenitic stainless steels.…”