Direct observation of the cleavage plane of sapphire by in-situ indentation TEM

Sasaki, Takeo; Shibata, Naoya; Matsunaga, Katsuyuki; Yamamoto, Takahisa; Ikuhara, Yuichi

doi:10.2109/jcersj2.120.473

Cited by 9 publications

(5 citation statements)

References 14 publications

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“…A structural rearrangement within the crack tip zone in sapphire manifested in formation of metastable Al-O-Al clusters at its fracture surface has been recently reported [24].…”

Section: Introductionmentioning

confidence: 91%

“…It should be noted that substitution of (24,38) into the effective free energy, (17) yields the LPT free energy:…”

Section: The Overcritical Solutionmentioning

confidence: 99%

“…The latter is by the factor of 2 2/3 larger than V c1 . Since the overcritical solution (24) for δη is determined by the same eignfunction (38) as that for the high-temperature case, the distribution, δη(r) = ξ 2 Ψ * (r) has the same form as that of the order parameter in the high-temperature PZ. The distribution is shown in Fig.…”

Section: The Process Zone Embedded Into the Daughter Phasementioning

confidence: 99%

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Transformational process zone emerging at the tip of a propagating crack

Boulbitch¹,

Korzhenevskii²

2015

Preprint

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Process zone at the tip of a propagating crack engendered by the stress-induced local phase transition of the second order is studied theoretically. We show that the zone can only exist within a certain domain of the phase diagram at one side of the phase transition line depending upon the sign of the striction constant. We obtain the boundary of this domain and establish its dependence upon the crack velocity. We show the existence of a critical crack velocity above which the zone cannot exist. We report the overcritical solution for the order parameter describing the incipient process zone, while far from the bifurcation point we solve the problem numerically.

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“…A structural rearrangement within the crack tip zone in sapphire manifested in formation of metastable Al-O-Al clusters at its fracture surface has been recently reported [24].…”

Section: Introductionmentioning

confidence: 91%

“…It should be noted that substitution of (24,38) into the effective free energy, (17) yields the LPT free energy:…”

Section: The Overcritical Solutionmentioning

confidence: 99%

Section: The Process Zone Embedded Into the Daughter Phasementioning

confidence: 99%

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Transformational process zone emerging at the tip of a propagating crack

Boulbitch¹,

Korzhenevskii²

2015

Preprint

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“…Thereafter, TEM in situ straining became popular for clarification of the dislocation dynamics in various materials with face-centered cubic (fcc) [ 6 , 9 , 10 , 11 ], body-centered cubic (bcc) [ 12 , 13 , 14 ], and hexagonal close-packed structures [ 15 , 16 ] during plastic deformation at various temperatures. For brittle fracture, Ikuhara et al [ 17 ] developed a TEM indentation holder working at elevated temperatures and reported the crack propagation by intra- and intergranular fracture in polycrystalline alumina at 1073 K. This indentation technique has been applied to several ceramic materials with brittle nature, such as magnesium oxide, silicon nitride, and sapphire (α-Al 2 O 3 ) [ 18 , 19 , 20 , 21 ]. To clearly visualize the dislocations introduced during TEM in situ indentation experiments, Kondo et al [ 22 , 23 ] recently used a double-tilt indentation holder and characterized an individual dislocation in a SrTiO 3 single crystal and well-oriented SrTiO 3 bicrystals with Σ5 and small-angle grain boundaries.…”

Section: Introductionmentioning

confidence: 99%

Direct Characterization of the Relation between the Mechanical Response and Microstructure Evolution in Aluminum by Transmission Electron Microscopy In Situ Straining

et al. 2021

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Transmission electron microscopy in situ straining experiments of Al single crystals with different initial lattice defect densities have been performed. The as-focused ion beam (FIB)-processed pillar sample contained a high density of prismatic dislocation loops with the <111> Burgers vector, while the post-annealed specimen had an almost defect-free microstructure. In both specimens, plastic deformation occurred with repetitive stress drops (∆σ). The stress drops were accompanied by certain dislocation motions, suggesting the dislocation avalanche phenomenon. ∆σ for the as-FIB Al pillar sample was smaller than that for the post-annealed Al sample. This can be considered to be because of the interaction of gliding dislocations with immobile prismatic dislocation loops introduced by the FIB. The reloading process after stress reduction was dominated by elastic behavior because the slope of the load–displacement curve for reloading was close to the Young’s modulus of Al. Microplasticity was observed during the load-recovery process, suggesting that microyielding and a dislocation avalanche repeatedly occurred, leading to intermittent plasticity as an elementary step of macroplastic deformation.

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“…Thus, post-mortem characterization by atomic-resolution TEM is often carried out to obtain detailed information at the atomic level. For alumina, crack propagation (Sasaki et al 2012;Kondo et al 2019) and dislocation formation phenomena (Miao et al 2019) have been investigated by in situ indentation and atomic structure analysis so far.…”

mentioning

confidence: 99%

TEM Characterization of Lattice Defects Associated with Deformation and Fracture in α-Al2O3

Tochigi

Miao

Kondo

et al. 2022

The Plaston Concept

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Alumina (α-Al2O3) is one of the representative structural ceramics. To understand its mechanical responses, the lattice defect behavior of alumina has been investigated by transmission electron microscopy (TEM) for many years. In this report, we review our recent research progress on TEM structural analysis of lattice defects in alumina. In the first half, the core atomic structure and dissociation reaction of b = $$1/3<11\bar{2}0>$$ 1 / 3 < 11 2 ¯ 0 > , $$<1\bar{1}00>$$ < 1 1 ¯ 00 > , and $$1/3<\bar{1}101>$$ 1 / 3 < 1 ¯ 101 > dislocations formed in low-angle grain boundaries are investigated by atomic-resolution TEM observations. Based on experimental results, the slip deformation behavior associated with those dislocations is discussed. In the second half, the formation of $$1/3<11\bar{2}0>$$ 1 / 3 < 11 2 ¯ 0 > dislocations and fracture of Zr-doped ∑13 grain boundary of alumina are observed by in situ TEM nanoindentation. Furthermore, these indented samples were observed by atomic-resolution scanning TEM. The mechanisms of the deformation and fracture phenomena are discussed in detail.

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Direct observation of the cleavage plane of sapphire by in-situ indentation TEM

Cited by 9 publications

References 14 publications

Transformational process zone emerging at the tip of a propagating crack

Transformational process zone emerging at the tip of a propagating crack

Direct Characterization of the Relation between the Mechanical Response and Microstructure Evolution in Aluminum by Transmission Electron Microscopy In Situ Straining

TEM Characterization of Lattice Defects Associated with Deformation and Fracture in α-Al2O3

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