TRANSIENT INTERNAL DAMPING IN ALUMINUM-BASED METAL-MATRIX COMPOSITES

This paper aims at describing the properties of the transient low frequency internal damping (ID) that has been observed in aluminium reinforced with 12 vol.% SiC particles. On cooling, the ID is characterized by a broad, poorly defined maximum (range 150-250 K) whose magnitude is increased with increasing cooling rate or decreasing frequency or amplitude of oscillation. The unreinforced material does not exhibit this phenomenon. It is interpreted in terms of the emission and movement of dislocations induced by the variation in internal stresses around particles, which is due to the thermal expansion mismatch between the Al matrix and SiC particles.