Abstract
In order to study the anisotropy of fracture toughness and fracture mechanism of single-crystal sapphire, the three-point bending tests and the single-edge V-notch beam (SEVNB) were used to test the fracture toughness of A-plane, C-plane, and M-plane sapphire, which are widely used in the semiconductor, aerospace, and other high-tech fields. Fracture morphology was investigated by a scanning electron microscope and three-dimensional video microscopy. The fracture toughness and fracture morphology of different crystal planes of sapphire showed obvious anisotropy and were related to the loading surfaces. C-plane sapphire showed the maximal fracture toughness of 4.24 MPa·m1/2, and fracture toughness decreases in the order of C-plane, M-plane, and A-plane. The surface roughness is related to the dissipation of fracture energy. The surface roughness of the fracture surface is in the same order as C-plane > M-plane > A-plane. The fracture behavior and morphology of experiments were consistent with the theoretical analysis. C-plane sapphire cleavages along the R-plane with an angle of 57.6 degrees and the rhombohedral twin were activated. M-plane and A-plane sapphire cleavages along their cross-section.
Highlights
Due to their ultra-high hardness, wear resistance, corrosion resistance, and excellent light transmittance, sapphire materials are widely used in the aerospace industry, national defense [1], optical industry, substrate manufacturing, etc. [2]
The fracture toughness and mechanism of different crystal plane orientations were studied, which can be used as the basis for industrial material selection and machining to avoid the great harm caused by brittle fracture at low stress
The results showed that the activation of the twin/slip system has an important influence on the sapphire indentation morphology [22]
Summary
Due to their ultra-high hardness, wear resistance, corrosion resistance, and excellent light transmittance, sapphire materials are widely used in the aerospace industry, national defense [1], optical industry, substrate manufacturing, etc. [2]. The fracture toughness and mechanism of different crystal plane orientations were studied, which can be used as the basis for industrial material selection and machining to avoid the great harm caused by brittle fracture at low stress. To study the mechanism of crack propagation and fracture damage evolution of sapphire with different crystal orientations, Luan et al performed dynamic and quasistatic indentation tests on the c-plane and a-plane of sapphires by Hopkinson pressure bar tester and continuous indentation tester, respectively. To study the anisotropy of single-crystal tal sapphire with different crystal orientations, the result of fracture toughness, displacesapphire with different crystal orientations, the result of fracture toughness, displacementment-load curves, and fracture surface roughness were compared.
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