Electrical and thermal conductivity of discontinuously reinforced aluminum composites at sub-ambient temperatures

The electrical and thermal conductivities of two SiC particle-reinforced aluminum-matrix composites were measured over the temperature range of 80-300 K. Because of the relatively low value of electrical conductivity of the SiC, the composite conductivity data agreed closely with;hose of the matrix with spherical pores, as predicted by the theory of Maxwell. The experimental data for the thermal conductivity of the composite exceeded the values predicted for the matrix phase with spherical holes, indicative of a contribution by the silicon carbide reinforcement. This contribution was significant at the higher temperatures but approached zero at the lowest temperature levels. Data analysis suggested that this effect could be attributed to a decrease in the thermal conductance at the Al-SiC interface with decreasing temperature, due to a corresponding increase in phonon scattering or other mechanisms. (C) 1997 Acta Metallurgica Inc.