中文摘要：

分别在3个不同的温度范围内对7050铝合金熔体施加超声振动,研究超声施振对熔体冷却时间及凝固组织的影响,并分析超声细化组织的机理。实验结果表明：超声振动在不同的温度范围内对熔体冷却时间的影响不同,在670～655℃和640～625℃温度范围内施振时,熔体的冷却时间长于未施加超声的时间;在625～590℃施振时,熔体的冷却时间明显短于未施加超声的时间,约为其三分之一;在640～625℃对熔体连续施加超声振动所得到的凝固组织细化效果明显好于施振温度范围为625～590℃;计算结果表明超声波引起的声流和机械效应不能直接折断枝晶臂;在超声振动的搅拌下,初生枝晶二次臂根部熔断是重要的细化机制。

英文摘要：

Ultrasonic vibration was imposed on 7050 aluminum melt in three different range of temperature.Effect of ultrasonic vibration on 7050 aluminum melt cooling was studied and the mechanism of grain refinement by ultrasonic was analyzed.The experiment results show that the effect of ultrasonic vibration on cooling time of alloy melt at different range of temperature is different.The cooling time of the alloy melt,on which the ultrasonic vibration is applied,when the temperature ranges are from 655 ℃ to 670 ℃ and from 625 ℃ to 640 ℃ is longer than that without ultrasonic vibration;however,when the temperature is between 590 ℃ and 625 ℃,it is obviously shorter,which is about one third of the time of which the vibration is not applied.Refinement effect of 7050 alloy solidification structure under the condition of the temperature of applying vibration from 640 ℃ to 625 ℃ is better than that from 625 ℃ to 590 ℃.According to the calculation,acoustic streaming and mechanic effect,which is caused by ultrasonic vibration can＇t break dendrite arm directly.The detachment of primary dendrite side arm by melting is a very important mechanism of refinement with the application of ultrasonic vibration.