Comparison of the Creep and Creep Rupture Performance of Two HIPed Silicon Nitride Ceramics

Ferber, Mattison K.; Jenkins, Michael G.; Nolan, T.A.; Yeckley, R. L.

doi:10.1111/j.1151-2916.1994.tb05345.x

Cited by 53 publications

(41 citation statements)

References 16 publications

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“…Tensile Creep: Creep deformation in tension is attributed to viscous flow of the intergranular phase and dilation of the structure so that rigid grains may slide past each other 65,74 . Unaccommodated strain in tension is the result of cavity formation, both at multigrain junctions and along the boundaries between grain pairs 24,65,66,68,71,75,76 . Cavities are nucleated to relieve the stresses that build up as a result of viscous flow and grain boundary sliding, 76 and are most commonly found at multigrain junctions.…”

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confidence: 99%

Microstructure and Creep Behavior of Silicon Nitride and SiAlONs

Fox¹,

Hellmann²

2008

Int J Applied Ceramic Tech

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Microstructural evolution of silicon nitride (Si3N4) and SiAlON materials and its influence on creep resistance is reviewed. Grain size, grain morphology, and the ratio of α‐ to β‐phase grains play a part in resistance to creep. The glassy, intergranular phase typically has the strongest influence on creep. Creep data are usually obtained using uniaxial tensile or compressive tests, where creep in tension is controlled by cavitation and grain boundary sliding controls creep in compression. The impression creep methodology is also reviewed. An additional creep mechanism, dilation of the SiAlON grain structure, was found to be active in impression creep.

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confidence: 99%

Microstructure and Creep Behavior of Silicon Nitride and SiAlONs

Fox¹,

Hellmann²

2008

Int J Applied Ceramic Tech

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“…In the last two decades, there has been growing recognition that the properties of Si 3 N 4 materials are significantly influenced by the grain-boundary phases present [13][14][15][16][17][18][19]. Since a basic understanding of the intergranular phase and structures is essential if improvements in the performance of silicon nitride are to be achieved, extensive research has been done on the characterization of the grain-boundary phases of silicon nitride materials.…”

Section: Introductionmentioning

confidence: 99%

The microstructure and boundary phases of in-situ reinforced silicon nitride

Liu

Nemat‐Nasser

1998

Materials Science and Engineering: A

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The microstructure of an in-situ reinforced silicon nitride, gas pressure sintered with La 2 O 3 , Y 2 O 3 , and SrO additives and then heat treated, is examined with X-ray diffraction, SEM, and high-resolution TEM. Two crystalline rare-earth apatite phases, La 5 Si 3 O 12 N and Y 5 Si 3 O 12 N, are identified at the grain pockets and at the two-grain boundaries. The thickness of the crystalline phases at the two-grain boundaries is approximately 1.7 nm, in compliance with the suggested equilibrium intergranular spacing. A glassy phase is also present at the grain pockets and at the two-grain boundaries due to incomplete crystallization of the boundary phases. The thickness of the amorphous phase at the two-grain boundaries varies from 0.7 to 3.0 nm, suggesting that compositional inhomogeneities exist in these areas. Based on the microstructural observations, the structures of the crystalline boundary phases, the equilibrium intergranular film thickness, and the mechanisms causing incomplete recrystallization of the glassy phase in the in-situ reinforced silicon nitride are discussed.

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“…12,[20][21][22][23][24][25][26] Creep cavities strain tensor transformation and it does not reflect the contribuform predominantly inside the glassy phases at the two-grain tion of the additional volume created by cavitation. Dilatational and multigrain junctions [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][19][20][21][22][23][24][25][26] and each cavity is directly strain, ε e , is not equal to creep strain at constant volume for the transformed into an increment of tensile strain. 12 In compressame reason.…”

Section: Analysis Of the Role Of Cavitation During Uniaxial Creepmentioning

confidence: 99%

“…Experimental Determination of the such a mechanism is restricted to the first 0.025-0.1% strain Role of Cavitation and cannot produce the strains of several percent observed in Equations (5) and (6) suggest two methods to separate true many ceramics. [3][4][5][6][7][8][9][10][11][12][13][14]26,29 The true value of ␣ needs to be detertensile strain from cavitational strain. The first method involves mined independently, for example, from comparison with the density change method.…”

Section: Analysis Of the Role Of Cavitation During Uniaxial Creepmentioning

confidence: 99%

Cavitational Strain Contribution to Tensile Creep in Vitreous Bonded Ceramics

Lofaj

Okada

Kawamoto

1997

Journal of the American Ceramic Society

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Analysis of the role of cavitation during uniaxial creepThe contribution of cavitation to tensile strain can be quantideformation in vitreous bonded ceramics reveals that the tatively determined by separating true creep strain from the cavity volume contributes only to the strain in the direction total tensile strain actually measured during creep tests. The parallel to the tensile stress regardless of the shape and basic method for such separation was suggested by Raj 23 from orientation of cavities. Creep asymmetry results from the the analysis of the diagonalized strain tensor expressed in terms fact that cavitation preferentially contributes to axial tensile of the principal strains ε 1 , ε 2 , and ε 3 . Generally, deformation in strain while the strain observed under the same conditions solids consists of a combination of volume change and change in compression is produced only by volume-conserving in shape. Dilatational strain corresponding to the volume mechanisms. The contribution of cavitational strain in the change is defined by axial tensile strain is equal to the volume fraction of cavities ⌬ ϭ (1 ϩ ε 1 )(1 ϩ ε 2 )(1 ϩ ε 3 ) Ϫ 1 and proportional to the difference between tensile and compressive strains in the axial direction. The density change which gives ⌬ Ϸ ε 1 ϩ ε 2 ϩ ε 3 for small strains. Distortional method and a newly proposed method based on the differstrain, ε e , representing the shape change, can be determined by ence in the axial strains were used for separating the cavitasubtracting one third of the dilatational strain from each of the tional from the true tensile strain in self-reinforced silicon strain components. Such a strain tensor transformation in the nitride. Both methods consistently revealed more than 90%case of the uniaxially deformed cylindrical specimen led to contribution of cavitation to the total tensile strain. Cavitathe expression 23 tion is concluded to be the dominant mechanism of tensile creep deformation in vitreous bonded ceramics because the ε e ϭ ε 1 Ϫ 1 3 |⌬| reported volume fractions of cavities during their deformation are usually in the range of 70-90% of tensile strain.This relation was used for the estimation of the cavitational strain contribution during tensile creep assuming that ⌬ is I. Introduction equivalent to the density change due to cavitation and ε e to the true creep strain at constant volume. 10 For a volume change N UMEROUS creep studies carried out on vitreous bonded equal to ϳ90% of total tensile strain measured in silicon nitride ceramics, 1-20 such as silicon nitride, siliconized silicon carit was concluded that cavitation is not an important part of bide, and alumina, have revealed that intensive creep cavitation tensile strain. 10 However, the volume change ⌬ results from the is intrinsic to tensile creep deformation. 12,20-26 Creep cavities strain tensor transformation and it does not reflect the contribuform predominantly inside the glassy phases at the two-grain tion of the additional volume created by cavitation. Dilatational and mul...

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Comparison of the Creep and Creep Rupture Performance of Two HIPed Silicon Nitride Ceramics

Cited by 53 publications

References 16 publications

Microstructure and Creep Behavior of Silicon Nitride and SiAlONs

Microstructure and Creep Behavior of Silicon Nitride and SiAlONs

The microstructure and boundary phases of in-situ reinforced silicon nitride

Cavitational Strain Contribution to Tensile Creep in Vitreous Bonded Ceramics

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