Influence of mosaicity on the fracture behavior of sapphire

Graça, S.; Trabadelo, V.; Neels, Antonia; Kuebler, Jakob; Nader, Victor Le; Gamez, G.; Döbeli, M.; Wasmer, Kilian

doi:10.1016/j.actamat.2013.12.004

Cited by 38 publications

(30 citation statements)

References 35 publications

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“…The values of K IC for the various crack directions of A-plane and C-plane sapphire are given in Figure 10. These values are smaller than those that are obtained from Graça [4], Newcomb [26], and Wunderlich [27]. Because the dwell period employed was 10 s, the crack has sufficient time to propagate, and relieve the stress.…”

Section: Analysis Of Indentation Fracture Morphologymentioning

confidence: 57%

“…Single-crystal sapphire (α-Al 2 O 3 ) is one of the hardest natural minerals (nine on the Mohs' scale) [1,2], and is widely used in industry, national defense, aerospace, and scientific research fields due to its superior chemical and physical properties [3,4]. In particular, A-plane sapphire is used as the screen panels and keyboards of smart phones, and C-plane sapphire is employed as substrates in electronic devices.…”

Section: Introductionmentioning

confidence: 99%

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

Wang

Jiang

et al. 2017

Crystals

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Single-crystal sapphire (α-Al 2 O 3) 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).

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Section: Analysis Of Indentation Fracture Morphologymentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

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

Wang

Jiang

et al. 2017

Crystals

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“…In addition, this plane is known to have a significantly lower fracture toughness (K Ic ) value compared to the toughness for the c-and m-planes. It is also close to the weakest R-plane (Graça et al, 2014). Thus, it can be concluded that lateral cracks, and chipping, are favored to grow along the a-plane.…”

Section: Discussion Of Materials Quality Model (Section 34)mentioning

confidence: 82%

Parametric experimental study and design of experiment modelling of sapphire grinding

Wasmer

Pochon

Sage

et al. 2017

Journal of Cleaner Production

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a b s t r a c tThis study investigates and models the grinding process of single crystal sapphire. Five parameters: the wheel speed, the feed speed, the vertical feed, the ultrasonic assistance and the crystallographic direction were considered via a design of experiments (DoE) approach. The responses were multiple but can be divided in three groups: the process, the machine and the grinding quality. DoE results revealed that the parameters interact in a complex manner and depends on the responses. Therefore, to gain a better understanding of the grinding process of sapphire, the interactions between parameters have also to be taken into consideration. It was found that three main parameters have the largest influences on the tangential grinding forces: the wheel speed, the feed speed and the vertical feed. In contrast, the median defect area is mainly impacted by the quadratic effects of the wheel speed and vertical feed followed by various interactions. After an optimization procedure, the second optimum for the tangential forces was found to be very close to the best optimum for the median defect area. The optimum solution is: a wheel speed of 7 0 500 rpm, a feed speed of 60 mm/min, a vertical feed of 12.5 mm/pass, no ultrasonic assistance and grinding along the c-axis. This set of parameters was validated with additional and repeated tests on both Verneuil and Kyropouloas sapphire. Finally, it came out that the optimum solution has also a very good productivity.

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“…The UTS falls off to 3.7 GPa; whereas the failure strain decreases to 4% at 1600 K. Comparing stress strain graphs of Figs. (a) and (b), the magnitude of the UTS for M‐plane is about half of that of C‐plane; which is consistent with Graca et al Moreover, the slow rate of changes in stresses between 2% and failure suggests the presence of plastic deformation prior to failure in M‐plane at all temperatures, representing a ductile‐like fracture behavior.…”

Section: Resultsmentioning

confidence: 99%

“…For this purpose, Montagne et al studied the room‐temperature deformation behavior and fatigue of sapphire for four main crystallographic orientations of <0001>, <10−10>, <1−210>, and <−1012>, corresponding to the C, M, A, and R planes, respectively . Others have also studied the fracture behavior anisotropy and the influence of mosaicity on the fracture behavior of sapphire …”

Section: Introductionmentioning

confidence: 99%

Multiscale Modeling of the Nanodefects and Temperature Effect on the Mechanical Response of Sapphire

2016

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A multiscale approach using Bridging Cell Method (BCM) is applied to simulate the combined effect of temperature and alumina's common structural nanodefects such as nanovoids, precracks, and Mg impurities on the mechanical response of single crystal C-plane and M-plane sapphire. The BCM model consists of three domains of continuum, bridging, and atomistic, where the whole system is solved in a finite element (FE) framework. Interatomic interaction potentials and temperaturedependent formulations are incorporated in the atomistic domain to conduct simulations for structures containing nanodefects at a range of finite temperatures from 300 to 1600 K. The results are compared for each case to analyze the effect of temperature and nanodefects. Mechanical response of the material is presented and discussed with respect to ultimate tensile strength (UTS), stress distribution and elasticity. Results show different material behavior for C-plane and M-plane under the same biaxial loading conditions but containing different nanodefects. Precracks are found to be the most critical defects for both systems, which significantly reduce structural strength. J ournalcontinuum domain boundary and V k , A k , and t k are volume, area, and traction of element k, respectively.Having E c calculated, the stiffness of the continuum domain, K c , could be obtained as:

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Influence of mosaicity on the fracture behavior of sapphire

Cited by 38 publications

References 35 publications

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

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

Parametric experimental study and design of experiment modelling of sapphire grinding

Multiscale Modeling of the Nanodefects and Temperature Effect on the Mechanical Response of Sapphire

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