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<p>Silicon carbide (SiC) ceramics are renowned for their exceptional mechanical properties under extreme conditions. However, the complex fracture mechanisms within coupled temperature-strain rate fields—particularly the link between microstructure and macroscopic response—remain inadequately understood. This raises a fundamental question: Is there a universal, competitive, and synergistic mechanism at the atomic scale—interacting among crystal structure, pre-existing defects, temperature, and strain rate—that governs the fracture mode transition in 3C-SiC? To explore this, we develop a comprehensive computational framework using molecular dynamics simulations, which encompass pristine single crystals and polycrystalline structures containing central cracks. Our simulations reveal a critical grain size of approximately 8&#xa0;nm in polycrystalline systems, where optimal mechanical performance (ultimate stress of 48.92&#xa0;GPa) is achieved. This marks the transition between the Hall–Petch and inverse Hall–Petch effects, with results aligning well with theoretical predictions (d_critical ≈ 7.9&#xa0;nm). Additionally, we observe a significant 246.7% increase in the strain rate sensitivity coefficient as temperature rises from 300 to 1500&#xa0;K (from 0.045 to 0.156), indicating a fundamental shift from brittle fracture to quasi-plastic deformation. Stress contour analysis further identifies three distinct fracture modes governed by the temperature-strain rate coupling: brittle cleavage (low temperature/high strain rate), microvoid coalescence (medium temperature/medium strain rate), and quasi-plastic network fracture (high temperature/high strain rate). These findings provide essential insights into the micro-damage mechanisms of SiC under extreme conditions and establish a microstructural foundation for optimizing ceramic material performance in next-generation aerospace and energy systems.</p>

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Mapping the fracture regimes of nanocrystalline 3C-SiC: a multi-parameter molecular dynamics study on grain size, crack, and thermo-mechanical loading

  • 期刊论文

  • 发表日期：

    2025年10月30日

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  • Qiuyan Li,
  • Chaokun Song,
  • Kang Guan,
  • Zhenya Lu,
  • Xiaohui Yang,
  • Longteng Bai,
  • Qingfeng Zeng,
  • Jiantao Liu

摘要

Silicon carbide (SiC) ceramics are renowned for their exceptional mechanical properties under extreme conditions. However, the complex fracture mechanisms within coupled temperature-strain rate fields—particularly the link between microstructure and macroscopic response—remain inadequately understood. This raises a fundamental question: Is there a universal, competitive, and synergistic mechanism at the atomic scale—interacting among crystal structure, pre-existing defects, temperature, and strain rate—that governs the fracture mode transition in 3C-SiC? To explore this, we develop a comprehensive computational framework using molecular dynamics simulations, which encompass pristine single crystals and polycrystalline structures containing central cracks. Our simulations reveal a critical grain size of approximately 8 nm in polycrystalline systems, where optimal mechanical performance (ultimate stress of 48.92 GPa) is achieved. This marks the transition between the Hall–Petch and inverse Hall–Petch effects, with results aligning well with theoretical predictions (d_critical ≈ 7.9 nm). Additionally, we observe a significant 246.7% increase in the strain rate sensitivity coefficient as temperature rises from 300 to 1500 K (from 0.045 to 0.156), indicating a fundamental shift from brittle fracture to quasi-plastic deformation. Stress contour analysis further identifies three distinct fracture modes governed by the temperature-strain rate coupling: brittle cleavage (low temperature/high strain rate), microvoid coalescence (medium temperature/medium strain rate), and quasi-plastic network fracture (high temperature/high strain rate). These findings provide essential insights into the micro-damage mechanisms of SiC under extreme conditions and establish a microstructural foundation for optimizing ceramic material performance in next-generation aerospace and energy systems.