E-Thesis 469 views
Reconstruction, Characterization, and Micromechanics of Polycrystalline Nickel-Based Superalloy at Mesoscopic Scale / BINGBING CHEN
Swansea University Author: BINGBING CHEN
DOI (Published version): 10.23889/SUthesis.63720
Abstract
In recent years, extensive correlation studies have been conducted between microstructure characterizations and macroscopic properties and performance in polycrystalline materials. These studies have revealed that the mechanical properties, including stress-strain curve, stress and strain response (...
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Swansea, Wales, UK
2023
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Chenfeng, Li. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa63720 |
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| Abstract: |
In recent years, extensive correlation studies have been conducted between microstructure characterizations and macroscopic properties and performance in polycrystalline materials. These studies have revealed that the mechanical properties, including stress-strain curve, stress and strain response (peak strength, effective stress, crack damage stress, ultimate tensile strength, yield stress, Von Mises stress, Tresca stress, effective strain, cumulative effective plastic strain, etc.), and elastic and plastic anisotropy, are closely connected to and significantly affected by morphological (grain size, grain size heterogeneity, grain shape, etc.) and crystallographic (grain orientation, etc.) features. Meanwhile, the influence of microstructure characterization on the mechanical performance of polycrystals has also been examined by researchers. It has been well established that ductile failure initiation and growth in polycrystals are extremely sensitive to crystallographic (grain orientation, etc.) and grain boundary (coincidence site lattice (CSL), misorientation, tilt and twist angle, etc.)conditions. However, in current practice, studies of the microstructure effect on ductile failure have certain limitations. For example, the research methodologies are mainly limited to representative volume elements (RVEs)-based experimental observations or crystal plasticity numerical simulations. In practice, the microstructure characterizations exhibit some degree of randomness during deformation processing, and microstructure randomness reveals polycrystalline materials’ probabilistic properties and performance. Consequently, the vast size and number of the microstructure RVE necessary to build the process–structure–properties–performance (PSPP) linkages is computationally prohibitive and challenging to investigate. Meanwhile, the simplified polycrystalline microstructures, such as single crystals, bicrystals, Voronoi and ellipsoid polycrystals, fail to capture all the statistical microstructure characterizations of the heterogeneous grains. Furthermore, to the author’s knowledge, these features that influence ductile failure are still contentious, and the association between microstructure characterizations and ductile failure in polycrystals is not yet wholly researched. In addition, it is difficult to quantify the impact of microstructure on ductile failure in polycrystalline materials without a straightforward and efficient method. In the end, the datasets between microstructural characteristics and ductile failure are unlikely to be built without sufficient data. This research comprehensively investigated the recent progress in microstructure reconstruction and characterization (MCR) of polycrystalline materials. After that, the patch-based texture synthesis reconstruction algorithm was proposed to perfectly capture the statistical microstructure characterizations of the heterogeneous grains. The crystal plasticity finite element (CPFEM) method that can reflect the stress-strain response in nickel-based superalloy was established to reveal the ductile failure mechanisms. Then, the established CPFEM model combined with explicit characterization algorithms was used to perform quantitative analysis on Inconel 718 superalloy to fully understand the macroscopic properties and performance responses (ultimate tensile strength (UTS), Von Mises stress, ductile failure initialization and propagation) in terms of morphological, crystallographic, and boundary characteristics. Finally, the patch-based texture synthesis coupled with explicit characterization algorithms was developed to determine the ductile failure sets using the microstructural parameters, such as grain orientation and boundary characters. Research conclusions can be excellent guidance for microstructure sensitive design (MSD), materials knowledge system (MKS), uncertainty quantification (UQ), and surrogate crystal plasticity modeling (SCPM) in polycrystalline materials. |
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| Keywords: |
Computational, Materials, Science |
| College: |
Faculty of Science and Engineering |