A MODIFIED ULTRASONIC INTERFEROMETER FOR SOUND-VELOCITY MEASUREMENTS IN MOLTEN METALS AND ALLOYS

An ultrasonic interferometer has been developed for measuring compress ional wave velocity (V(p)) and attenuation (or conversely, quality fac tor Q(p)) in molten Fe, Fe-Ni, Fe-Ni-S, and Fe-Ni-Si alloys. Results f or pure molten Fe are presented. A radio frequency (rf) induction tech nique is used for heating that allows a +/- 1 K temperature stability at 1973 K. The effects of the electromagnetic field interaction with t he molten conductive metal are discussed in terms of applicability to V(p) and Q(p) measurements. Considerations of acoustic impedance and t hermal absorption are presented to discuss the high-temperature use of polycrystalline Al2O3 buffer rods for velocity and attenuation measur ements. Viscoelastic theories, when applied to pure molten Fe, predict an extremely small acoustic coefficient of attenuation. Suggestions a re made to circumvent the experimental difficulties encountered in att enuation measurements.