Tensile Creep Performance of a Developmental, In-Situ Reinforced Silicon Nitride

Wereszczak, A. A.; Kirkland, T. P.; Lin, Hua‐Tay; Ferber, Mattison K.; Li, C.‐W.; Goldacker, Jeffrey

doi:10.1002/9780470294444.ch6

Cited by 7 publications

(7 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(i) Si 3 N 4 creeps much faster in tension than in compression. 5,20,[26][27][28][29][30][31][32] Figure 1 illustrates this behavior, where the logarithm of the minimum creep rate for several different silicon nitrides is plotted as a function of the logarithm of the applied stress. At the same stress, the tensile creep rate is anywhere from 10 to 100 times greater than the compressive creep rate.…”

Section: (2) Experimental Observationsmentioning

confidence: 99%

“…This behavior occurs in at least five grades of Si 3 N 4 . 5,[18][19][20]32,36,37 In comparison, the compressive creep rate is a power-law function of the applied stress; values of n generally range from ∼1 5,27,28,30,[38][39][40][41][42][43][44][45][46][47] to ∼2. 39,40,[48][49][50][51] (iii) Cavity formation produces the bulk of the tensile creep strain in Si 3 N 4 .…”

Section: (2) Experimental Observationsmentioning

confidence: 99%

See 1 more Smart Citation

A New Model for Tensile Creep of Silicon Nitride

Luecke

Wiederhorn

1999

Journal of the American Ceramic Society

View full text Add to dashboard Cite

The tensile creep rate of most commercial grades of Si 3 N 4 increases strongly with stress. Although the usual powerlaw functions can represent the creep data, the data often show curvature and systematic variations of slope with temperature and stress. In this article, we present a new approach to understanding the creep of ceramics, such as Si 3 N 4 , where a deformable second phase bonds a deformation-resistant major phase. A review of experimental data suggests that the rate of formation and growth of cavities in the second phase controls creep in these materials. The critical step for deformation is the redistribution of the second phase away from the cavitation site to the surrounding volume. The effective viscosity of the second phase and the density of active cavities determine the creep rate. Assuming that the hydrostatic stresses in pockets of the second phase are normally distributed leads to a model that accurately describes the tensile creep rate of grades of Si 3 N 4 . In this model, the creep rate increases exponentially with the applied stress, is independent of Si 3 N 4 grain size, is inversely proportional to the effective viscosity of the deformable phase, and is proportional to the cube of the volume fraction of the deformable phase.

show abstract

Section: (2) Experimental Observationsmentioning

confidence: 99%

Section: (2) Experimental Observationsmentioning

confidence: 99%

A New Model for Tensile Creep of Silicon Nitride

Luecke

Wiederhorn

1999

Journal of the American Ceramic Society

View full text Add to dashboard Cite

show abstract

“…The dependence of the failure time on stress and temperature can be represented by recognizing that the Monkman-Grant relation 40 correlates the secondary or minimum creep rates and times to failure, t f , in both metals and ceramics. In particular, for silicon nitride the correlation sometimes depends on temperature: 41,42…”

Section: (2) Creep Rupture Lifetimementioning

confidence: 99%

Tensile Creep and Rupture of Silicon Nitride

Krause

Luecke

French

et al. 1999

Journal of the American Ceramic Society

View full text Add to dashboard Cite

We have characterized the tensile creep, rupture lifetime, and cavitation behavior of a commercial, gas-pressuresintered silicon nitride in the temperature range 1150°to 1400°C and stress range 70 to 400 MPa. Individual creep curves generally show primary, secondary, and tertiary creep. The majority of the primary creep is not recoverable. The best representation of the data is one where the creep rate depends exponentially on stress, rather than on the traditional power law. This representation also removes the need to break the data into high and low stress regimes. Cavitation of the interstitial silicate phase accompanies creep under all conditions, and accounts for nearly all of the measured strain. These observations are consistent with a model where creep proceeds by the redistribution of silicate phase from cavitating interstitial pockets, accommodated by grain-boundary sliding of silicon nitride.

show abstract

“…NT164 (Norton Advanced Ceramics, Northboro, MA) silicon ni@ide contained a secondary phase that did not change with time [11] and its creep rate and lifetime incidentally were not apparently dependent on speeimen size in one study [12]. SN5-L silicon nitride exhibited an apparent specimen size effect in creep and contained as-received seeondary phases that changed during creep testing; however, unlike SN88, larger SN5-L tensile speeimens had better creep resistance [4]. Lastly, GN 10 silicon nitride contained non-equilibrated secondary phases and its creep deformation was apparently dependent on specimen size [5][6].…”

Section: Iiie Secondary Phase Equilibrium and Specimen Sizementioning

confidence: 99%

“…35 mm diameter), respectively.s Differences in the creep rate have also been observed for SN5-L (AlliedSignal, Morristown, NJ) [4] and GN1O (AlliedSignal, Torrance, CA), see Fig. 1 [5][6], silicon nitrides when two or more different test specimen geometries were used for the testing.…”

mentioning

confidence: 94%