Thermal expansion behavior of particulate metal-matrix composites

Aluminum-matrix composites containing thermally oxidized SiC particles of controlled diameter ranging from 3 to 40 mu m have been produced successfully by vacuum-assisted high-pressure infiltration. Their thermal-expansion coefficients (CTEs) were measured between 25 and 500 degrees C with a high-precision thermal mechanical analyser (TMA), and compared with the predictions of various theoretical models. The thermal-expansion behavior of the three-phase Al/SiC/SiO2 composite shows no significant deviation from the predictions of elastic analysis, since the measured CTEs lie within the elastic bounds derived by Schapery's analysis. The effect of particle size is quite evident in the pressure-infiltrated composites: the larger the particles, the greater the thermal expansion of the composite. The observed behavior of these composites is discussed in terms of particle size, silica layer formed during oxidation, and thermal stresses developed as LL result of the CTE mismatch between the reinforcement and the matrix. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.