| High intensity ultrasonic is based on physics,mechanics,material and so on.it is an applied technology that changes some aspects of objects or properties, or its speed is changed by ultrasonic energy. High intensity ultrasonic treatment is one of the effective ways to improve solidification struction,macro-segregation and mechanical properties of the metal in the process of metal solidification. This paper main study aluminum ultrasonic effect in the process of metal solidification was shown as follows:First of all, it is Describe the power ultrasonic cavitation, acoustic streaming and attenuation characteristics, The effect of power ultrasound on solidification process of melt metal mechanism and aluminum melt thermodynamics,kinetics as well as the nucleation and The macro-segregation of the elements were reserched in the end, which provided a academic basis for the proceeding of experiments and their results analysis.Secondly, The effects of ultrasonic treatment on solidification characteristics was studied bases on the thermal analysis method.The critical nucleus, maximum nucleation rate, characteristic points involving the final temperatures of nucleation and solidification have been determined on the basis of the thermal analysis cooling and cooling rate curves.The experiment results show that ultrasound field has a significant effect on the solidification process of pure Al. Increasing the power of ultrasound can decrease the cooling temperature is increase and decrease the nucleation time so as the overall solidification time is. solidification process mode of aluminum melt without ultrasound treatment is the layer-by-layer,under ultrasonic treatment tend to volume solidification model. and the temperature field can become more uniform and decrease temperature gradient with the application of ultrasonic field.Besides, 7050 aluminum alloy of Zn, Mg, Cu elements of macro-distribution under ultrasonic field were studied.the solute elements in 7050 alloy could be made homogeneous under ultrasonic field,the negative segregation phenomena of Cu was deleted and the segregation of Mg was decreased.The macro-segregation of the elements Zn,Mg and Cu in 7050 Al alloy was decreased with the application of ultrasonic field with different powers during solidification.In the present thesis, The casting ingot structure refining laws of the different ultrasonic powers was analyzed.With increasing of ultrasonic power,more refined structure can be obtained. However, when the ultrasonic power reaches a certain value,the effect of refining grains is not increased significantly.experiment results showed: different temperatures range of the aluminum melt applying vibration,tmperature too high, too low will weaken the effect of refinement,there is an optimal temperature range 760～660℃applying vibration, ultrasonic power 240W and grain size is 67μm .There is a law between ultrasonic power and the average grain size, meeting exponential relationships , which provide an experimental basis for industrial applications of ultrasonic Fine-grained technology.Finally,Using different ultrasonic power on solidification process of aluminum alloy, comparison of different power ultrasound propagation direction along the solidification structure changes in the sample and found that the grain size of solidification structure of continuous decline in fine-grained effect getting worse, Fine-grained distance up to 260mm when ultrasonic power 240W. Came to the conclusion that the mathematical relationship between ultrasonic power and Fine-grained distance in the end, It has certain guide value for power ultrasonic effective treating metal melt used in industrial filed. |
PDF Full Text Request