A Model for Estimating Internal Stress during Sintering of Ceramic Multiphase Laminates

A mechanical model is proposed to estimate internal stress during sintering of ceramic multiphase laminates. A symmetrical multi-layered laminate is assumed, and one-dimensional elastic analysis is carried out on the change in stress of each layer during sintering, based on the differences in sintering strain, thermal expansion strain and phase transformation strain between the layers. By taking a limit such that the thickness of each layer approaches infinitesimally small, the internal stress expression can be extended into the case of the materials with continuous compositional change (viz. functionally gradient materials).

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Functionally Gradient 3YSZ-IN713LC Composites

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.47-50.5 ◽

2008 ◽

Vol 47-50 ◽

pp. 5-8

Author(s):

D.H. Kuo ◽

R.K. Shiue ◽

W.Y. Tseng ◽

C.H. Shih ◽

T.Y. Yeh ◽

...

Keyword(s):

Residual Stress ◽

Thermal Expansion ◽

Compressive Stress ◽

Coefficient Of Thermal Expansion ◽

Functionally Gradient Materials ◽

Monotonic Change ◽

Gradient Materials ◽

Linear Mode ◽

Functionally Gradient ◽

Fracture Behaviors

Functionally gradient materials (FGMs) composed of 3YSZ and IN713LC were developed in three different configurations. A linear-mode FGM had its compositions with a monotonic change in coefficient of thermal expansion (CTE). Negative- and positive-deviated FGMs had their compositions with lower and higher CTEs, respectively, on the ceramic sides. Fracture behaviors of these three types of FGMs were evaluated with aids of residual stress analyses. FGMs with a positive CTE deviation demonstrated the best performance in the experiment. The brittle ceramic side was under high compressive stress, and high tensile stresses were primarily initiated in the metal-rich gradient layers.

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Synthesis of free standing, one dimensional, AlSiC based functionally gradient materials using gradient slurry disintegration and deposition

Materials Science and Engineering A ◽

10.1016/s0921-5093(99)00262-2 ◽

2000 ◽

Vol 276 (1-2) ◽

pp. 210-217 ◽

Cited By ~ 10

Author(s):

M Gupta ◽

C.Y Loke

Keyword(s):

Functionally Gradient Materials ◽

Free Standing ◽

Gradient Materials ◽

One Dimensional ◽

Functionally Gradient

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Microstructural and Microchemical Characterization of Nickel Sulfide Inclusions in Plate Glass

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100089123 ◽

1991 ◽

Vol 49 ◽

pp. 962-963

Author(s):

J. Cooper ◽

O. Popoola ◽

W. M. Kriven

Keyword(s):

Thermal Expansion ◽

Phase Transformation ◽

Glass Matrix ◽

Nickel Sulfide ◽

Plate Glass ◽

Thermal Expansion Mismatch ◽

Volume Increase ◽

Β Phase ◽

Microchemical Characterization

Nickel sulfide inclusions have been implicated in the spontaneous fracture of large windows of tempered plate glass. Two alternative explanations for the fracture-initiating behaviour of these inclusions have been proposed: (1) the volume increase which accompanies the α to β phase transformation in stoichiometric NiS, and (2) the thermal expansion mismatch between the nickel sulfide phases and the glass matrix. The microstructure and microchemistry of the small inclusions (80 to 250 μm spheres), needed to determine the cause of fracture, have not been well characterized hitherto. The aim of this communication is to report a detailed TEM and EDS study of the inclusions.

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Transformation behavior of yttria stabilized tetragonal zirconia polycrystal–TiB2 composites

Journal of Materials Research ◽

10.1557/jmr.2001.0294 ◽

2001 ◽

Vol 16 (7) ◽

pp. 2158-2169 ◽

Cited By ~ 21

Author(s):

B. Basu ◽

J. Vleugels ◽

O. Van Der Biest

Keyword(s):

Thermal Expansion ◽

Phase Transformation ◽

Low Temperature ◽

Tetragonal Zirconia ◽

Mechanical Analysis ◽

Transformation Behavior ◽

Thermal Expansion Data ◽

Thermally Induced ◽

First Time ◽

Tetragonal Zirconia Polycrystal

The objective of the present article is to study the influence of TiB2 addition on the transformation behavior of yttria stabilized tetragonal zirconia polycrystals (Y-TZP). A range of TZP(Y)–TiB2 composites with different zirconia starting powder grades and TiB2 phase contents (up to 50 vol%) were processed by the hot-pressing route. Thermal expansion data, as obtained by thermo-mechanical analysis were used to assess the ZrO2 phase transformation in the composites. The thermal expansion hysteresis of the transformable ceramics provides information concerning the transformation behavior in the temperature range of the martensitic transformation and the low-temperature degradation. Furthermore, the transformation behavior and susceptibility to low-temperature degradation during thermal cycling were characterized in terms of the overall amount and distribution of the yttria stabilizer, zirconia grain size, possible dissolution of TiB2 phase, and the amount of residual stress generated in the Y-TZP matrix due to the addition of titanium diboride particles. For the first time, it is demonstrated in the present work that the thermally induced phase transformation of tetragonal zirconia in the Y-TZP composites can be controlled by the intentional addition of the monoclinic zirconia particles into the 3Y-TZP matrix.

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Enlarging the Temperature Range for Maximum Wear Resistance of TiNi Alloy Using a NTE Phase

Materials Science Forum ◽

10.4028/www.scientific.net/msf.539-543.3261 ◽

2007 ◽

Vol 539-543 ◽

pp. 3261-3266 ◽

Cited By ~ 2

Author(s):

Iulian Radu ◽

Dong Yang Li

Keyword(s):

Wear Resistance ◽

Thermal Expansion ◽

Internal Stress ◽

Frictional Heating ◽

Negative Thermal Expansion ◽

High Wear Resistance ◽

Tini Alloy ◽

Wear Loss ◽

Second Phase ◽

Temperature Range

The near-equiatomic TiNi alloy has been demonstrated to possess high wear resistance, which largely benefits from its pseudoelasticity (PE). However, the PE occurs only in a small temperature range, which makes the wear resistance of this alloy unstable as temperature changes, caused by environmental instability or frictional heating. Therefore, enlarging the working temperature of PE could considerably improve this alloy as a novel wear-resistant material. One possible approach is to develop a self-built temperature-dependent internal stress field by taking the advance of the difference in thermal expansion between the pseudoelastic matrix and a reinforcing phase. Such a T-dependent internal stress could adjust the martensitic transformation temperature to respond changes in environmental temperature so that the temperature range of PE could be enlarged, thus leading to a wide temperature range in which the minimum wear loss is retained. Research was conducted to investigate effects of an added second phase having a negative thermal expansion (NTE) coefficient on the wear resistance of a near-equiatomic TiNi alloy. It was demonstrated that the temperature range of this modified material in which the wear loss dropped was enlarged. In addition, the wear resistance of such a TiNi-matrix composite was on one order of magnitude higher than that of unmodified TiNi alloy.

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