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This study systematically investigated intergranular crack propagation characteristics along grain boundary (GB) networks in both conventional and grain boundary-engineered (GBE) austenitic stainless steels through comprehensive two-dimensional (2D) and three-dimensional (3D) microstructural analyses. The resistance to intergranular stress corrosion cracking (SCC) was quantitatively evaluated under simulated nuclear reactor coolant conditions. Microstructural characterization revealed distinct cracking susceptibility among different boundary types: ∑3 twin boundaries demonstrated exceptional cracking resistance, while ∑9 and ∑27 boundaries showed significantly reduced susceptibility. In contrast, random high-angle boundaries and other low-Σ coincidence site lattice (CSL) boundaries maintained similarly high vulnerability to SCC initiation. Notably, twin boundaries exhibited dual protective effects: intrinsic resistance to cracking and extrinsic shielding of adjacent boundaries, as manifested by decreased cracking probability in boundaries surrounded by higher fractions of neighboring twin boundaries. Mechanistically, crack propagation was frequently arrested at triple/quadruple junctions containing twin boundaries. The GBE-treated microstructure displayed substantially enhanced SCC resistance due to the formation of large-scale twin-related domains. Primary crack propagated in zigzag patterns along the outer boundaries of large twin-related domains, as their interiors predominantly consisted of highly resistant ∑3n-type boundaries. These morphologically complex, interwoven domains created substantial topological constraints, resulting in: (1) Mechanical interlocking that impeded crack advancement; (2) Formation of numerous crack-bridging ligaments on fracture surfaces; (3) Significant crack path deflection effects. The three-dimensional interconnectivity of these twin-related domains effectively distributed localized stresses, thereby substantially improving overall SCC resistance compared to conventional microstructures.

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Enhancing Resistance to Intergranular Cracking via Grain Boundary Engineering

  • 章节

  • 发表日期：

    2026年

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  • Tingguang Liu

摘要

This study systematically investigated intergranular crack propagation characteristics along grain boundary (GB) networks in both conventional and grain boundary-engineered (GBE) austenitic stainless steels through comprehensive two-dimensional (2D) and three-dimensional (3D) microstructural analyses. The resistance to intergranular stress corrosion cracking (SCC) was quantitatively evaluated under simulated nuclear reactor coolant conditions. Microstructural characterization revealed distinct cracking susceptibility among different boundary types: ∑3 twin boundaries demonstrated exceptional cracking resistance, while ∑9 and ∑27 boundaries showed significantly reduced susceptibility. In contrast, random high-angle boundaries and other low-Σ coincidence site lattice (CSL) boundaries maintained similarly high vulnerability to SCC initiation. Notably, twin boundaries exhibited dual protective effects: intrinsic resistance to cracking and extrinsic shielding of adjacent boundaries, as manifested by decreased cracking probability in boundaries surrounded by higher fractions of neighboring twin boundaries. Mechanistically, crack propagation was frequently arrested at triple/quadruple junctions containing twin boundaries. The GBE-treated microstructure displayed substantially enhanced SCC resistance due to the formation of large-scale twin-related domains. Primary crack propagated in zigzag patterns along the outer boundaries of large twin-related domains, as their interiors predominantly consisted of highly resistant ∑3n-type boundaries. These morphologically complex, interwoven domains created substantial topological constraints, resulting in: (1) Mechanical interlocking that impeded crack advancement; (2) Formation of numerous crack-bridging ligaments on fracture surfaces; (3) Significant crack path deflection effects. The three-dimensional interconnectivity of these twin-related domains effectively distributed localized stresses, thereby substantially improving overall SCC resistance compared to conventional microstructures.