Study Of Ultrasonic Smelting On Grain Refinement And Purifying Technology Of Aluminum Alloy

With the rapid development of economy,aluminum alloys have been widely applied in industrial production,especially in the light weight application of automobile.The grain refinement and melt purification of aluminum alloys have become a hot research direction.Power ultrasound has special potential capabilities for improving product quality,reducing production costs,preventing environmental pollution,and increasing production efficiency.It is great significance to understand the principle of ultrasonic stirring and select the reasonable parameters of ultrasonic stirring for improving the grain refinement and the degree of melt purification of the aluminum alloy.In this paper,ultrasonic stirring was applied to study the grain refinement and melt purification of aluminum alloy.The grain size and melt purification degree of aluminum alloy were analyzed through comparative experiments.The effects of ultrasonic treatment on the microstructures and properties of Al-7%Si alloy,the solidification structure of ZL101 A aluminum alloy and the melt purification are the main contents to be studied in this paper.The experimental studies of the effects of ultrasonic treatment on the microstructures and properties of Al-7%Si alloy showed that:(1)The porosity of the ingot can be reduced by 54% by ultrasonic stirring to the molten liquid metal and more than 95% of the pores are concentrated at the top of the ingot;(2)The ultrasonic stirring has the effect of grain refinement and eutectic silicon phase metamorphism.The average grain diameter can be decreased by 48% after ultrasonic stirring,and the average length width ratio of eutectic silicon can be decreased by 75%;(3)The addition of 1% Al Ti B master alloy under the ultrasonic stirring has the best effect on the grain refinement of the aluminum alloy,resulting in a decrease of 57% in the average grain diameter of the aluminum alloy.However,with the addition of the master alloy increases,the variation of average grain diameter of the alloy by less than 5%.Therefore,the effect of the increase of the amount of master alloy on grain refinement is not obvious.In order to further study the distribution and action of trace elements under ultrasonic stirring,the experiment of the effect of ultrasonic treatment on the solidification structure of ZL101 A aluminum alloy was studied.The experiment conclusion could be drawn as follows:(1)The ultrasonic stirring in ZL101 A aluminum alloy can reduce the porosity of the melt by 46%,and at the same time it can increase the solid solubility of the element and reduce the degree of element segregation in the grain boundary so as to improve the uniformity of the alloy;(2)The trace elements in ZL101 A aluminum alloy play a role of refining agent in the solidification process of alloy.Compared with the binary alloy,the average grain diameter of the alloy can be decreased by 24%,which makes the grain of the ingot further refined.In order to study the effects of ultrasonic stirring on the melt purification process,the experiment of the effect of ultrasonic treatment on the melt purification of aluminum alloy was studied.The following conclusions are obtained through experiments.(1)As the ultrasonic treatment time increases,the acoustic radiation produced by the sound pressure lasts longer,the stomatal area can be reduced by 85.6%,the resistivity can be decreased by 32.9% and the Brinell hardness can be increased by 33.5%;With the increase of ultrasonic power,high intensity cavitations and wide area of the acoustic flow effect make the stomatal area reduced by 15.6%,the resistivity decreased by 7.9%,and Brinell hardness increased by 7.9%;When the bottom of the ultrasonic probe is 20 mm from the solution surface,the acoustic flow distribution is the most uniform.The stomatal area can be reduced by 13.5%,the resistivity can be reduced by 5.3% and the Brinell hardness can be increased by 5.7%.The optimal experimental program for reducing the porosity includes ultrasonic treatment time 5min,ultrasonic power 200 W and the bottom of the ultrasonic probe is 20 mm from the solution surface.(2)Ultrasonic treatment can refine primary silicon,and the average size of ultrasonic treated primary silicon was reduced by 51.6% compared with untreated primary silicon.When the ultrasonic treatment time increased from 1min to 5min,the Si content in the sample can be decreased by 56.7% on average;when the ultrasonic power is 200 W,the content of Si in the sample can be decreased by 22.6% on average;when the bottom of the ultrasonic probe is 20 mm from the solution surface,the content of Si in the sample can be decreased by 3.5% on average.Therefore the optimal experimental program for reducing the inclusion content includes ultrasonic treatment time 5min,ultrasonic power 200 W and the bottom of the ultrasonic probe is 20 mm from the solution surface.(3)The results of orthogonal experiment of porosity content and inclusion content show that ultrasonic treatment can effectively purify aluminum alloy melt.The ultrasonic treatment time has the most obvious effect on the degree of melt purification,and the effects of the ultrasonic power and the distance from the bottom of the probe to the solution surface were not obvious.The optimal experimental program for optimal comprehensive performance includes ultrasonic treatment time 5min,ultrasonic power 200 W and the bottom of the ultrasonic probe is 20 mm from the solution surface.