The noncontacting nature of laser-based ultrasonic measurement has made it attractive in many high temperature materials processing applications. Locating and characterizing, the shape of the solidification front is of prime importance for the metal casting and refining industries. Since the laser ultrasonic approach requires only optical access to the free surface, it is well suited to molten metals, where immersion of the measurement probe is often not desired. This paper describes the results of an investigation of the information obtainable with laser ultrasonic methods using several different molten metals
