Journal ArticleDOI
Creep and creep fracture in hot-pressed alumina
TLDR
In this paper, the creep and fracture behavior of two hot-pressed aluminas are presented, for both flexural and tensile testing, and three distinct fracture regimes are found.Abstract:
The creep and creep fracture behavior of two hot-pressed aluminas are presented, for both flexural and tensile testing. Steady-state power-law creep is observed with a stress exponent of about 2 for each material. Three distinct fracture regimes are found. At high stress in flexure, fracture occurs by slow crack growth with a high stress dependence of the failure time. At intermediate stresses, in both flexure and tension, creep fracture occurs by multiple microcracking after modest strains. Failure times exhibit a modest stress dependence (stress exponent of 2.5 in tension and 3 in flexure), with a constant failure strain equal to 0.09. The failure times are considerably longer in flexure than in tension, because of the constraint imposed on crack growth by the bending geometry. We conclude that flexure cannot be used for creep lifetime assessment, even in simple, single-phase materials such as Al2O3. At low stresses, in tension, failure also exhibits a modest stress dependence but with a much higher failure strain. The material shows the onset of super-plastic behavior.read more
Citations
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Journal ArticleDOI
Evaluated Material Properties for a Sintered alpha-Alumina
TL;DR: In this article, a set of material property data is established based on published physical, mechanical, and thermal properties of alumina specimens that conform to the constraints of the material specification.
Journal ArticleDOI
Creep of duplex microstructures
TL;DR: The tensile creep behavior of two ceramic composite systems exhibiting duplex microstructures was studied relative to their single-phase constituents in the temperature and stress ranges of 1,100--1,350 C and 35--75 MPa.
Journal ArticleDOI
Role of segregating dopants on the improved creep resistance of aluminum oxide
TL;DR: In this article, it has been shown that outsize ions segregate to more favorable grain boundary sites, and improve creep resistance by blocking a few critical diffusive pathways, and this mechanism is sufficiently general that it may be applicable to other ceramic systems.
Journal ArticleDOI
Tensile Creep Behavior of Alumina/Silicon Carbide Nanocomposite
TL;DR: In this article, the authors investigated the tensile creep and creep rupture behaviors of alumina/17 vol% silicon carbide nanocomposite and monolithic alumina at 1,200 to 1,300 C and at 50 to 150 MPa.
Journal ArticleDOI
Dopant distributions in rare-earth-doped alumina
A. Mark Thompson,Kamal K. Soni,Helen M. Chan,Martin P. Harmer,David B. Williams,Jan M. Chabala,Riccardo Levi-Setti +6 more
TL;DR: In this article, the distribution of yttrium and lanthanum dopants in polycrystalline aluminas using imaging secondary-ion mass spectrometry (imaging-SIMS) was mapped.
References
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Journal ArticleDOI
Calculation of Stresses and Strains in Four-Point Bending Creep Tests
TL;DR: In this article, an analysis of strains and stresses in four-point bending creep tests in the limit of small beam deflections resulted in a general equation which relates the load-point deflection, the applied load, the creep exponent (N), and the geometrical parameters of the loading system.
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The shape of intergranular creep cracks gro′ing by surface diffusion
Chuang T′e-Jer,James R. Rice +1 more
TL;DR: In this article, the shape of the cavity surfaces is determined based on the assumption that this is governed by surface diffusion, and that steady state conditions prevail, so that the cavity advances as a profile retaining a constant shape near its tip.
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High temperature mechanical properties of single phase alumina
Atul H. Chokshi,John R. Porter +1 more
TL;DR: In this paper, the creep properties of a commercial, single phase aIurnina have been determined in the temperature range of 1623 to 1723 K. The stress exponent,n, in the relationship ǫ √ σ n ≥ 1.9 and the true activation energy was found to be 635 kJ mol−1.
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Overview 14 Creep fracture in ceramic polycrystals—I. creep cavitation effects in polycrystalline alumina
TL;DR: In this paper, the authors examined the evolution of cavities at grain boundaries and the contribution of cavitation to the creep rate and total creep strain in fine grained polycrystalline alumina.
Journal ArticleDOI
Duality in the Creep Rupture of a Polycrystalline Alumina
TL;DR: In this article, a duality in fracture behavior associated with a crack blunting threshold was observed in polycrystalline alumina, where failure occurs by the coalescence of creep damage, manifested as shear bands.