INTERNAL-FRICTION IN ALCU-AL2O3 METAL-MATRIX COMPOSITES

In metal-matrix composites (MMCs), the metal matrix is exposed to plastic deformation and damage: accumulation in the region close to the reinforcements, following mechanical or thermal stress. In this connection, A1-4 wt pet Cu-based MMCs reinforced with 20 vol pct Al2O3 fibers were characterized by internal friction (IF) measurements. The IF measurements as a function of the vibration amplitude present a solid friction peak connected with the loosening of metal-fiber interfaces, while plastic deformation was associated with a high amplitude IF background. On this basis, IF measurements allowed us to identify the distribution of internal stresses and damage accumulation at matrix-fiber interfaces or plastic flow in the matrix in different thermomechanical conditions.' Furthermore; IF measurements allowed damage accumulation consequent to mechanical fatigue to be followed.