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Talks and Poster Presentations (without Proceedings-Entry):

M. Schöbel, W. Altendorfer, H.P. Degischer, T. Buslaps, M. di Michiel:
"Residual stresses and void kinetics in particle reinforced metal matrix composites during thermal cycling";
Poster: Junioreuromat 2008, Lausanne; 07-14-2008 - 07-17-2008.



English abstract:
Particle reinforced metal matrix composites are developed for heat sink materials for example for power electronic devices because of their good thermal conductivity combined with a low coefficient of thermal expansion. A baseplate material with a low CTE is necessary to avoid delamination between the baseplate and the ceramic insulator. Highly conducting matrices with high volume fraction of heat conducting ceramic particles like SiC or diamond combine their properties for this application. Residual stresses are built up between the matrix and the reinforcements during temperature changes owing to a mismatch in thermal expansion. These stresses can cause debonding between the matrix and the reinforcements and/or damage in the matrix. The interface bonding quality is critical for the long term stability of the MMC during thermal cycles.

AlSiC MMCs are commonly used as baseplate material for power electronics. Diamond with the best known thermal conductivity is a promising reinforcement to increase the thermal conductivity of MMCs. Comparable studies on AlSiC and AlCD MMCs investigate the interface bonding quality and long term stability of these MMCs under thermal load. In situ residual stress analysis and micro tomography with synchrotron radiation sources reveal the changing void volume fractions related to the internal stresses created during thermal cycles. While the voids in AlSiC close during heating, those in AlCD open up. Residual stresses and the void kinetics are investigated by synchrotron tomography and diffraction. The combination of these methods pointed out as useful methods to determine reinforcement architectures and their effects on thermal fatigue.

Keywords:
MMC, heat sink, residual stresses, thermal fatigue, synchrotron

Created from the Publication Database of the Vienna University of Technology.