TRANSIENT INTERNAL DAMPING IN ALUMINUM-BASED METAL-MATRIX COMPOSITES

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