Influence of grain boundary and grain size on the mechanical properties of polycrystalline ceramics: Grain‐scale simulations

Abstract

The Orowan‐Petch relation is a famous model to describe the strength of polycrystalline ceramics covering a wide range of grain sizes. However, it becomes difficult to explain the strength trend when the grain size decreases to the sub‐microscale or nanoscale. This is because some microstructural parameters (such as grain size, grain boundary fracture energy, and grain boundary defects) vary with different processing technologies, and their coupling effects on mechanical properties are still unclear. In this study, a finite element method (FEM) was applied to investigate the dependence of mechanical properties, such as strength and damage resistance, on the abovementioned microstructural parameters on example of alumina. The numerical results show that the grain boundary energy is weakly coupled with the grain size and grain boundary defects. The grain size and grain boundary are intercoupling, which affects mechanical properties. The mechanical properties could be improved by increasing the grain boundary fracture energy and decreasing the grain size and the grain boundary defect density.

Numerical Study of Thermal Shock Damage Mechanism of Polycrystalline Ceramics

“…The cohesive zone model (CZM) (Dugdale, 1960;Barenblatt, 1962;Needleman, 1990) was applied to simulate the crack initiation and propagation in the RVE model. The detail construction method of the RVE model can be found in our previous work (Gong et al, 2020). To build a connection between the RVE model and the macroscale model, as Figure 1 shown, the mechanical parameters for the macroscale model were obtained from RVE models.…”

“…Therefore, RVE models with grain sizes of 70 nm, 300 nm, 500 nm, 700 nm, 3 μm, and 5 μm under 1 J/m 2 and a grain boundary fracture energy of 1, 1.2, 1.5, and 5.2 J/m 2 under 700 nm grain size were simulated, respectively, under the unidirectional tensile load to obtain apparent critical fracture strength and apparent fracture energy. Our previous work (Gong et al, 2020) had calculated the mechanical parameters of these RVE models, and the apparent fracture strength and apparent fracture energy are listed in Table 2.…”

Ultrahigh-Strength Porous Ceramic Composites via a Simple Directional Solidification Process

“…According to the Griffith theory of brittle strength, conventional dense ceramics could obtain improvements in their strength σ by an increase of fracture toughness K 1c and a reduction of defect size c . , With regard to porous ceramics, the pore characteristic is an extra key of their strength . In this context, the linear relationship between ln σ and P has been demonstrated by experimental data and is commonly expressed as σ = σ 0 e – BP , where σ is the strength of the porous body, σ 0 is the strength of a nonporous body of the same material, P is the volume fraction of pores, and B is the slope of the ln σ vs P curve .…”

Finite element analysis of fracture behavior in ceramics: Prediction of strength distribution using microstructural features

“…[15][16][17] In recent years, this method has been applied to grainscale analysis, resulting in the potential of investigating the effect of the grain size on the stochastic fracture behavior. 18 Moreover, the finite element analysis (FEA) methodology was proposed to predict the strength scatter of ceramics based on microstructural data, including the relative density, grain size distribution, and pore distribution. [19][20][21] In addition, this approach, which is within the framework of FEM, can examine the fracture probability of components with various shapes under various boundary conditions.…”