Observation and control of solidification processes by ultrasonic pulse-echo technique

For the solidification of metals and semiconductors, the solidification velocity and the thermal gradient at the solid-liquid interface are the most relevant parameters. They are crucial for the formation of well-defined microstructures. We have developed an ultrasonic pulse-echo technique to observe and control the solidification velocity in various applications. The paper shows the principle set-up of the technology and gives an overview of the solidification processes it has been used for.