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M. Schöbel, H.P. Degischer, S. Vaucher, M. Hofmann, P. Cloetens:
"Reinforcement architectures and thermal fatigue in diamond particle reinforced aluminum";
Acta Materialia, 58 (2010), 6421 - 6430.

Aluminium reinforced by 60 vol.% diamond particles is investigated as a potential heat sink material for high power electronics. Diamond (CD) is used as reinforcement contributing its high thermal conductivity (TC ~ 1000 W/mK) and low thermal expansion (CTE ~ 1 ppm/K). An Al-matrix enables the shaping and joining of the composite component. Interface bonding is improved by limited carbide formation induced by a heat treatment and even more by SiC coating of the diamond particles. AlSi7 matrix forms an interpenetrating composite of a 3D network of diamond particles linked by Si bridges percolated by ductile α-Al matrix. Internal stresses are generated during temperature changes due to the CTE mismatch of the constituents. The stress evolution is determined in situ by neutron diffraction during thermal cycling between room temperature and 350 °C (soldering temperature). Tensile stresses build up in the Al/CD-composites: during cooling < 100 MPa in pure Al matrix, around 200 MPa in Al of the AlSi7 matrix. Compressive stresses build up in Al during heating of the composite. The stress evolution causes changes in the void volume fraction and interface debonding by visco-plastic deformation of the Al-matrix. Thermal fatigue damage is revealed by high resolution synchrotron tomography. The interconnected diamond-Si 3D network formed with the AlSi7-matrix promises a higher stability with respect to cycling temperature exposure.

particulate reinforced composites; neutron diffraction; synchrotron radiation computed tomography; thermal cycling; internal stresses

http://publik.tuwien.ac.at/files/PubDat_193930.pdf