(1. 中南大學(xué) 機(jī)電工程學(xué)院，長沙 410083；
2. 中南大學(xué) 現(xiàn)代復(fù)雜裝備設(shè)計與極端制造教育部重點(diǎn)實驗室，長沙 410083)
摘 要: 采用SPECTRO-MAXx立式直讀光譜儀和Leica金相顯微鏡，研究超聲功率對半連鑄過程中7050鋁合金微觀組織及溶質(zhì)Zn元素徑向分布的作用規(guī)律。結(jié)果表明：在超聲外場作用下鑄錠組織明顯細(xì)化，混晶減少，溶質(zhì)Zn元素的徑向逆偏析程度減弱，并隨著超聲功率的增加，晶粒細(xì)化程度及宏觀偏析的弱化效果更好，溶質(zhì)Zn元素的偏析比由未加超聲時的1.190降低為240 W功率超聲作用時的1.086；在超聲外場調(diào)控下，鋁合金熔體偏析弱化的主要原因是由于形核率增加，晶粒細(xì)化，兩相區(qū)液固相相對運(yùn)動速度減小；液穴變淺，由鑄錠收縮導(dǎo)致的富集液相徑向流動減弱，是徑向偏析程度減弱的另一原因；在半連續(xù)鑄造過程中，采用超聲外場控制液相的流動是弱化鑄錠徑向宏觀偏析的有效手段。
關(guān)鍵字: 7050鋁合金；半連鑄；逆偏析；超聲；空化；偏析比
（1. College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Modern Complex Equipment Design and Manufacturing, Ministry of Education,
Central South University, Changsha 410083, China）
Abstract:The macro-distribution of solute elements Zn and microstructure for 7050 aluminum alloy by semi-continuous casting under the ultrasonic field were investigated by SPECTRO-MAXx and Leica optic microscopy. The results show that the microstructure refines, the duplex structure consisting of coarse-cell and fine-cell dendritic grains decreases, the inverse segregation grade of Zn decreases effectively. With the increase of the ultrasonic power, the microstructure becomes finer and more uniform, the distribution of solute elements is more harmonious, the segregation ratio of Zn through 240 W ultrasonic treatment decreases to 1.086 from 1.190 without ultrasonic. After being treated by ultrasonic field, the nucleation ratio of the Al melt increases, the microstructure refines, the relative velocities of the solid and liquid phases in mushy zone decreases, and the shrinkage-induced flow of the enriched solute decreases due to the sump height decreases, which suppresses macro-segregation in a great degree. The liquid phases flow controlled by ultrasonic field is an effective means to weaken the macro-segregation in semi-continuous casting.
Key words: 7075 aluminum alloy; semi-continuous casting; inverse segregation; ultrasonic; cavitation; segregation ratio
