Effect Of Longitudinal And Transverse Vibration Of Ultrasonic Radiator On Cavitation And Refining Region Of Aluminum Melt

Abstract:During the process of aluminum alloy casting treated by ultrasonic vibration, the ultrasonic radiator is immersed in melt and transfers ultrasound into aluminum melt, the vibration characteristic of which has important influence on sound field, cavitation region and the microstructure refining of ingot. This paper aims at the effect of longitudinal and transverse vibration of ultrasound radiator on cavitaion region and microstructure refining, and the study was conducted as follows:1.Vibration test was done for a piezoelectric ultrasonic transducer for casting by laser range finder, the displacement amplitude distribution of end and cylindrical surface was gained through amplitude spectrum correction for the vibration series based on interpolation method. The test results show that longitudinal vibration was the major vibration and there existed transverse vibration on cylindrical surface.The max amplitude of transverse vibration reached1/2of the longitudinal vibration amplitude2. The dynamic characteristics of piezoelectric ultrasonic transducer for casting were studied based on ANSYS. The vibration test result was discussed by modal and harmonic analysis. The finite element model of infinite fluid region was established, and the sound field distribution under different depth of ultrasonic vibration in water and aluminum melt was calculated. The acoustic pressure amplitude distribution nearby the end and cylindrical surface was gained and the result show that there appears two acoustic radiation region nearby the end and cylindrical surface when the depth of vibration was increased, the max acoustic pressure on cylindrical surface can reach1/3of acoustic pressure on end surface.3. The influencing factors of cavitation threshold were analyzed and the cavitation region was pre-estimated combined with the acoustic pressure field distribution in water and melt. The experiment of cavitation erosion of aluminum foil in water and ultrasound radiator in melt were done to verify the pre-estimation of cavitation region. The distribution of cavitation region was gained and the results indicated that both the longitudinal and transverse vibration of ultrasound radiator can generated cavitaion in aluminum melt and the cavitation region expanded with the increasing of the depth of vibration.4. The experiments of ultrasonic casting of aluminum alloy were carried out when the depth of ultrasonic vibration applying on melt was respectively10mm,40mm,70mm.1/2of ingot section were sampled and the equiaxial and dendritic grains distribution was gained. The result show that the microstructures below the end surface were all refined equiaxed grains with different depth of ultrasonic vibration applying on melt.the microstructures above the end surface could be refined when the depth of ultrasonic vibration was respectively40mm,70mm. The refining Equiaxed region reached the maximum when the depth of ultrasonic vibration was70mm. The analysis result indicated that the cavitation region nearby the cylindrical surface could expand the refining region above the end surface.Above research preliminary analyzed the effect of longitudinal and transverse vibration of ultrasound radiator on cavitation and refining region of aluminum melt, which is of certain guiding significance for the designing of ultrasound radiator and efficient utilization of ultrasonic energy. With50figures,4tables, and77references...