ISSN:
1662-8985
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Joining Si3N4 and Al2O3 using 15 layers has been achieved by a unique approach thatintroduces SiAlON polytypoids as a functionally graded material (FGM) bonding layer. Previously,the hot press sintering of multilayered FGM with 20 layers, each 500 µm thick, has been achievedsuccessfully. In the present study, the number of layers for FGM was reduced from 20 to 15 toincrease optimization. Samples were fabricated by hot pressing at 48 MPa during the temperatureramp to 1650°C and cooling at 2°C/min to minimize residual stresses from sintering. Moreover, afinite element method (FEM) program based on the maximum principal stress theory and themaximum tensile stress theory was applied to design optimized and reduced FGM layers thatproduced a crack-free joint. The sample had a 3-dimensional cylindrical shape that was transformedto a 2-dimensional axisymmetric mode. By determining the expected thermal stress from thecalculated elastic modulus and coefficient of thermal expansion, we were able to predict andprevent damage due to thermal stresses. These analyses are especially useful for FGM sampleswhere it is very difficult to measure the residual stresses experimentally. Finally, oriented Vickersindentation testing was used to qualitatively characterize the strengths of the joint and the variousinterfaces. The indentation cracks were deflected at the SiAlON layers, implying weak interfaces. Inother areas, cracks were not deflected, implying strong interfaces
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.47-50.494.pdf
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