Effects of melt-treatment with low power ultrasonic

such as output power density

stirring time

ultrasonic vibration temperature and mould pre-heating temperature on microstructure of LC9 alloy were investigated.The results show that LC9 alloy with spherical or granular primary grain can be prepared by controlling parameters of melt-treatment with low power ultrasonic and solidification conditions.The size of primary phase tends to be decreased with increasing in ultrasonic power density within 0～5 W/cm2.With ultrasonic power density more than 5 W/cm2

the grain size change can be ignored.With the increase of stirring time or ultrasonic vibration temperature

grain size is decreased firstly

and then increased

and critical value of stirring time and ultrasonic vibration temperature is 45 s and 660 ℃

respectively.The grain size is increased rapidly with increasing in the preheating temperature of mold in range of room temperature to 450 ℃.The spheroidization effect of ultrasonic is weaken when the preheating temperature is higher than 300 ℃.