With the help of the HYSCAN Ⅱ apparatus to measure hydrogen content in every experimented melt

effects and mechanism of ultrasonic vibration with varied frequency on the degassing process of commercial pure Al（99.7% in weight）and 7050 aluminum alloy melt were investigated by introducing ultrasonic in different temperature ranges.The results reveal that hydrogen content in the melt is evidently decreased after ultrasonic treatment.Hydrogen content in the melt is increased with rising in temperature.When melt temperature is located at 660～720℃

degassing effects are increasingly improved with decreasing in temperature

however

degassing efficiency is almost independent of the melt temperature.At fixed power and temperature

degassing effects and efficiency with 15Hz are obviously superior to those with 20Hz.The ultrasonic cavitation plays an important role in generating plenty of cavitation bubbles

furthermore

frequency exhibits a decisive role in cavitation bubble growth and in diffusion of hydrogen in melt.