INTERNAL FRICTION AND DYNAMIC MODULUS OF METAL MATRIX COMPOSITES AND ADVANCED ALLOYS

The PUCOT (piezoelectric ultrasonic composite oscillator technique) has been used at frequencies near 100 kHz to measure internal friction and dynamic Young's modulus of various metal matrix composites (MMCs) and advanced alloys. The materials in the study were : Al/SiC MMCs with up to 20 volume % SiC and powder metallurgy (PM) Al-Fe-X alloys denoted as 452 and B014L. The testing was performed at various temperatures ranging from room temperature to over 300°C. The strain amplitude dependence of internal friction was investigated over the strain range 10-8 to 10-4. The modulus data were fitted to a linear equation of the type : E = E(0) - MT, where E (GPa) is the dynamic modulus at temperature T (°C), E(0) is the modulus at 0°C and M is the slope dE/dT in GPa/°C. The values of M for the materials studied varied in the range 0.03 to 0.10 GPa/°C, while values of M/E(0) (= -(1/E) (dE/dT)) fell in the interval (4 to 9) x 10-4 °c-1. The effects of a flash anneal (540°C for 5 minutes) on the dynamic modulus (measured at room temperature) for the PM (Power Metallurgy) Aluminum specimens was also investigated. The PUCOT is described, and the damping and dynamic modulus data are discussed