Numerical Simulation And Experimental Studies Of Cavitation Induced By Ultrasound In7Xxx Aluminum Alloy Melt

Treating metal melt by ultrasonic is a pollution-free Metallurgical technology. In the process of metal solidification, applying ultrasonic vibration can refine grain, improve the structure, reduce casting defects and improve the properties of materials, and becomes the hot spot in the field of casting nowadays and the development direction of the future casting technology. This paper focuses on the simulation of cavitation effect induced by applying ultrasonic vibration to the aluminum alloy melt. The main research and results are as follows:1. According to the thermodynamics and kinetics of metal crystallization, the bubble resonance mechanism induced by ultrasonic vibration in molten aluminum alloy was studied, the energy transfer and crystal vibration frequency of aluminum alloy influenced by cavitation effect was analyzed, the results show that:the ultrasonic vibration can significantly improve the vibration frequency and vibration energy of crystal nucleus.2. By using the displacement sensor and the hydrogen instrument named ALSCAN, the amplitude of ultrasonic horn under different power and the hydrogen content in7050aluminum alloy melt were measured. The ultrasonic parameters were added to the model using UDF (User Define Function),and coupling with Singhal cavitation model, simulation results show that:under the action of the low power, near the surface of ultrasonic horn end appears the stable cavitation, and the intensity of cavitation is weak; and under the action of the higher power, the intensity and region of cavitation are greatly improved. The cavitation simulation of three different type ultrasonic horn shows that:under the action of conical ultrasonic horn, the cavitation region is the largest, but the cavitation intensity and the uniformity of bubble distribution is the worst; and under the action of flat ultrasonic horn, the cavitation region is minimum, but it has highest intensity; while under the action of spherical ultrasonic horn, the cavitation intensity and region are between the other two,but the uniformity of bubble distribution is the best.3. The three different ultrasonic horn were used in water simulation test and casting test of7050aluminum alloy. In the water simulation test, the flat one got the maximum cavitation and acoustic streaming intensity but with a smaller radiation radius; the spherical got a relatively larger radiation radius and intensity; the conical got the maximum radiation radius but the weakest intensity with the fastest declining speed. Simulation and experimental results were in good agreement.By the casting test of7050aluminum alloy, the flat got the best microstructure, followed by the spherical and then the conical.