Plastic Deformation of Fine‐Grained Alumina (Al<sub>2</sub>O<sub>3</sub>): I, Interface‐Controlled Diffusional Creep

Cannon, R. M.; Rhodes, W. H.; Heuer, A. H.

doi:10.1111/j.1151-2916.1980.tb10648.x

Cited by 326 publications

(78 citation statements)

References 19 publications

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“…Other reported values for the lattice diffusion coefficient ( l D ) vary from 10 15 to 10 11 cm 2 /s in the temperature range from 1100 to 1500 ℃, the boundary diffusivity ( gb D  ) from 10 18 to 10 14 cm 2 /s [19,20]. These values are very low, which suggests that no matter whether the diffusion is through the lattice or through the grain boundary, the diffusion distance should be on the order of 1 μm in the temperature range from 1000 to 1500 ℃.…”

Section: Discussionmentioning

confidence: 99%

“…The diffusion coefficients of Al 3+ and O 2 ions through the lattice and grain boundary in aluminum oxide are well documented [19,20]. The following equations show one set of relationships for the diffusion coefficient of Al 3+ ions through the lattice ( l D ) and through the grain boundary ( gb D ) [19]:…”

Section: Discussionmentioning

confidence: 99%

“…The following equations show one set of relationships for the diffusion coefficient of Al 3+ ions through the lattice ( l D ) and through the grain boundary ( gb D ) [19]:…”

Section: Discussionmentioning

confidence: 99%

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Oxidation mechanism of aluminum nitride revisited

Yeh

Tuan

2017

J Adv Ceram

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Different from the oxidation kinetics of other nitrides, the oxide layer on AlN can easily reach tens of micrometers at a temperature above 1200 ℃. In the present study, the oxidation mechanism of AlN is investigated through microstructure observation. The analysis indicates that the oxide layer is full of small pores. The formation of pores generates additional surface area to induce further reaction. The reaction thus controls the oxidation in the temperature range from 1050 to 1350 ℃. The oxidation rate becomes slow as the oxide layer reaches a critical thickness.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Oxidation mechanism of aluminum nitride revisited

Yeh

Tuan

2017

J Adv Ceram

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“…Grain boundaries (GBs) have a significant influence on important sintering processes such as densification [1], grain growth [2], creep [3][4][5], segregation [6,7], diffusion [8], as well as on electrical [9], mechanical [10], superconducting [11][12][13] and optical [14] properties. The importance of GBs on the overall properties of ceramics depends on several factors, including the density of GBs in the material, the chemical composition of the interface and the crystallographic texture, i.e.…”

Section: Introductionmentioning

confidence: 99%

CSL grain boundary distribution in alumina and zirconia ceramics

Vonlanthen

Grobéty

2008

Ceramics International

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The distributions of general and coincidence site lattice (CSL) grain boundaries (GBs) in texture-free alumina and zirconia ceramics sintered at two different temperatures were investigated based on electron backscatter diffraction (EBSD) measurements. Results were compared with the distributions obtained from random 2D spatial models and with calculated random distributions reported in the literature. All alumina samples independent on sintering temperature show the same characteristic deviations of the measured general GB distributions from the random model. No such features can be seen in zirconia. The total fractions of CSL GBs in alumina and zirconia samples are clearly larger, for both sintering temperatures, than those observed in the random simulations. A general GB prominence factor, similar to the twin prominence factor for fcc metals, was defined to simplify the representation of the CSL GB content in zirconia. The observed deviations from the random model show no dependence on sintering temperature nor on lattice geometry. In alumina, however, the change in the CSL GB character distribution with sintering temperature seems to be crystallographically controlled, i.e. directly dependent on the orientation of the CSL misorientation axis.

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“…concerned with the vacancy creati nihilation process at boundar-ies, or with impediments to grain boundary sl·idh1g (as , unspecified) 16. It is tempting to invoke the non-linearities con ined in dislocation models of grain boundary creep 17 • But.…”

Section: The Transitionmentioning

confidence: 99%

Creep Fracture in Ceramic Polycrystals—i. Creep Cavitation Effects in Polycrystalline Alumina

Porter

Blumenthal

Evans

1983

Perspectives in Creep Fracture

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The measurements and the cavity observations are reported in the rst section. The observations are then compared with the predi ons of di fusive cavitation models, to establish the merit of such models for characterizing cavitation in this class of polycrystal. Finally, the models are used to examine the influence of cavi tion on the creep deformation under various conditions of stress and temperature. RESULTS AND OBSERVATDeformation tests were conducted on exural specimens at constant displacement rates. The plastic strain levels achieved in the were determined from the separation of scribes placed on the side surface of tThe material was a hot pressed Al 2 0 3 /0o25% MgO with an average grain size of rv2]Jm. T.he Cavity ShapeThe near·~ti p sha ) the upper bound cavity width, w , can be predicted. For the cavity shown in figure 6 the upper bound value of the cavity width is 224 nm. compared th a meas nm. For each case, examined in this way, the measured width was always less than the upper bound value and within a factor of 3. Considering the uncertainty in the diffusion parameter, these correspondences are considered to be sufficiently close to confirm that the observed crack-like cavities had indeed formed by a diffusive mechanism~ with surface diffusion as the ra limiting step. The TransitionThe transition from the equilibrium to crack-like cavity roorphology is dependent upon the stress level. the relative cavity size and the ratio 6 of the surface to boundary diffusivities 8 • 13 • The location of this transition is plotted in figure 7 for a temperature of l550K (0.15<6<0.5) 3 .The experimentally observed cavities can be placed on the transition diagram to examine conformance with the prediction. This is achieved by adopting implied by the cavity growth models. The observed non-linearity of the creep ra n ~1.8 ·is thus concluded to originate primarily from a non-l'i near c mechanismo The most likely origin of the non-linearity resiconcerned with the vacancy creati nihilation process at boundar-ies, or with impediments to grain boundary sl·idh1g (as , unspecified)16. It is tempting to invoke the non-linearities con ined in dislocation models of grain boundary creep 17 • But. it is di cult to envisa on the basis of the present observations that a sufficient fra ion of boundaries can be described by a discrete dislocation array permit such models to be applied with confidence. This is clearly an issue that meri further investigation.The extent of the deformation attributed to the cavitation can be predicted from models of uniform cavity arrays. The predictions are summa~ zed in figure 8. in terms of the parameter R • the cavitation creep rate relative to the Coble creep rate and f • the ratio of the crack length to crack spacing. For a typical value of I' J (i'J l). figure 8 shows that the proportion of the cavitation creep attributed to the growth of crack-like or full-facet cavities is less than that derived from equilibrium shaped cavities, by a factor of ~3. This prediction is

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Plastic Deformation of Fine‐Grained Alumina (Al₂O₃): I, Interface‐Controlled Diffusional Creep

Cited by 326 publications

References 19 publications

Oxidation mechanism of aluminum nitride revisited

Oxidation mechanism of aluminum nitride revisited

CSL grain boundary distribution in alumina and zirconia ceramics

Creep Fracture in Ceramic Polycrystals—i. Creep Cavitation Effects in Polycrystalline Alumina

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Plastic Deformation of Fine‐Grained Alumina (Al2O3): I, Interface‐Controlled Diffusional Creep

Cited by 326 publications

References 19 publications

Oxidation mechanism of aluminum nitride revisited

Oxidation mechanism of aluminum nitride revisited

CSL grain boundary distribution in alumina and zirconia ceramics

Creep Fracture in Ceramic Polycrystals—i. Creep Cavitation Effects in Polycrystalline Alumina

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Product

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Plastic Deformation of Fine‐Grained Alumina (Al₂O₃): I, Interface‐Controlled Diffusional Creep