Electron microscopy analysis for crack propagation behavior of alumina

• Published in: International journal of fatigue Vol. 32; no. 3; pp. 592 - 598
• Main Authors: Matsuo, H., Mitsuhara, M., Ikeda, K., Hata, S., Nakashima, H.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2010; Elsevier
• Subjects: Applied sciences; Electron tomography; Exact sciences and technology; Fatigue; High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM); High-resolution transmission electron microscopy (HR-TEM); Intergranular fracture; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Scanning electron microscopic electron back-scattered diffraction (SEM-EBSD); Transgranular fracture; Electron tomography; High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM); Scanning electron microscopic electron back-scattered diffraction (SEM-EBSD); Transgranular fracture; High-resolution transmission electron microscopy (HR-TEM); Intergranular fracture; Scanning electron microscopy; High resolution; Electron diffraction; Mechanical properties; High-angle annular dark-field scanning transmission electron microscopy (HAAF-STEM); Fatigue; Crack propagation; Transmission electron microscopy; Alumina
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2009.06.006

In order to clarify crack propagation behavior of alumina (α-Al 2O 3), intergranular and transgranular fractures of alumina were investigated by electron microscopy techniques. For the intergranular fractures cracked grain boundaries were investigated by scanning electron microscopic electron back-scattered diffraction (SEM-EBSD) analysis. It was revealed that the intergranular fracture behavior of polycrystalline alumina with random distribution of crystallographic orientations is independent on grain boundary characters. For the transgranular fractures, fracture surfaces formed in a single-crystalline alumina were observed by electron tomography combined with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and high resolution TEM (HR-TEM). Three kinds of fracture surfaces were observed: even fracture surfaces, even fracture surfaces with step-terraces and fracture surfaces composed of the even fracture surface and the curved one. The even fracture surfaces mostly consist of cleavage planes parallel to { 1 1 ¯ 0 2 } and { 1 1 ¯ 0 4 } . On the other hand, the even fracture surfaces with step-terraces consist of the cleavage planes and basal planes (0 0 0 1). For the fracture surfaces composed of the even fracture surface and the curved one, both the even and curved shapes the even parts were formed by the fine cleavage planes and basal planes, whose intervals were inhomogeneous. It was indicated that the fracture surfaces in alumina are composed of the cleavage planes or basal plane at an atomic scale.