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Open AccessArticle

Effects of Crystal Orientation on the Crack Propagation of Sapphire by Sequential Indentation Testing

by Ningchang Wang 1,2, Feng Jiang 1,2,*, Xipeng Xu 1,2 and Xizhao Lu 3
1
Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021, China
2
MOE Engineering Research Center for Brittle Materials Machining, Huaqiao University, Xiamen 361021, China
3
College of Mechanical Engineering and Automation, Huaqiao University, Xiamen 361021, China
*
Author to whom correspondence should be addressed.
Crystals 2018, 8(1), 3; https://doi.org/10.3390/cryst8010003
Received: 18 October 2017 / Revised: 15 December 2017 / Accepted: 20 December 2017 / Published: 25 December 2017
Single-crystal sapphire (α-Al2O3) is a hard and brittle material. Due to its highly crystalline nature, the fracture behavior of sapphire is strongly related to its crystal structure, and understanding the effects of crystal structure on the crack propagation of sapphire is essential for the successful application of this important material (e.g., as wafers in the electronics industry). In the present work, crack propagation that is induced by sequential indentation was investigated on the A-plane and C-plane of sapphire using a Vickers indenter on a micrometer scale. It was found that increasing indentation depth obviously increases the rate of crack propagation on the A-plane, but this effect is not so obvious on the C-plane because of the different slip systems induced by indentation on the different crystal planes of sapphire. Moreover, some parallel linear traces along the A-plane, which fracture with increasing indentation depth, are observed from the residual indentation on the A-plane. The fracture toughness of both A-plane and C-plane sapphire is smaller after indentation testing than that obtained using conventional testing methods. The subsurface damage was detected by transmission electron microscopy (TEM). View Full-Text
Keywords: sequential indentation test; crack propagation speed; crack system; fracture toughness sequential indentation test; crack propagation speed; crack system; fracture toughness
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Wang, N.; Jiang, F.; Xu, X.; Lu, X. Effects of Crystal Orientation on the Crack Propagation of Sapphire by Sequential Indentation Testing. Crystals 2018, 8, 3.

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