The ultrasonic velocity in a magnetic fluid (MF) on a base of water is measured under different temperatures, frequencies and magnetic fields. Two Kinds of ultrasonic correlation systems are employed. The maximum velocity is observed at 38°C without distinction of frequency. In the frequency range of 4∼10 MHz, a weak frequency dependence of ultrasonic velocity of 1∼2 m/s is observed. Dependence of external magnetic field in the magnetic field strength of 0∼±0.2 T is on the order of 10-4. An experiment with a magnetic fluid as an acoustic coupling medium is performed to demonstrate its usefulness in ultrasonic nondestructive evaluation (UNDE).
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