Ultrasonic imaging, particle detection, and V(z) measurements in molten zinc using focused clad buffer rods

Ultrasonic imaging, particle detection, and V(z) measurements have been per formed using focused clad buffer rods in molten zinc at temperature more th an 600 degrees C. The focused ultrasonic waves are generated by a spherical or cylindrical acoustic lens which is fabricated at the end of the clad bu ffer rod. In order to evaluate its focusing ability, several experiments ar e carried out at 10 MHz in a pulse-echo mode. The lateral resolution at the focus of the spherical acoustic lens in molten zinc is quantitatively exam ined and compared with that in water using a thin stainless wire with a dia meter of 380 mu m. High resolution ultrasonic imaging is carried out by the common C-scan technique. The signal-to-noise ratio of the reflected signal s from the flat sample surface at the focus is better than 35 dB. Ultrasoni c images are obtained from the amplitude and time delay variations of the r eflected signals. An attempt has also been made to detect particles suspend ed in molten zinc. Backscattered signals from particles are clearly visible at the focal region of the lens. For quantitative materials evaluation, V( z) curve measurements are performed using both spherical and cylindrical su rface lenses and the leaky surface acoustic wave velocity of a ceramic (SiC ) plate immersed in molten zinc is successfully determined. (C) 2000 Americ an Institute of Physics. [S0034-6748(00)00209-4].