Ultrasonic measuring techniques suitable for high temperature melts
for Doppler imaging, for the determination of densities and temperatures
and for the growth rate of the solidified fraction
Ultrasonic detection schemes based on phase sensitive detection respectively correlation techniques have been developed for the spatially resolved characterization of solidifying melts. With the aid of guided ultrasonic waves, the position of the solid-liquid interface of metallic alloys has been detected with high resolution under directional solidification conditions. Detection schemes based on focusing transducers suitable for Doppler imaging at 100 MHz with a resolution of the fluid velocity of typically 1 mm/s are demonstrated. Special probe configurations suitable for the detection of the density and the temperature of the liquid fraction and possible applications of synthetic aperture techniques for spatially resolved detection are discussed. The presentation of a variety of novel ultrasonic detection schemes has the aim to identify possible applications demanded for the processing of semiconductors, metals respectively alloys and other optically non-transparent media.