中文摘要：

采用SPECTRO-MAXx立式直读光谱仪和Leica金相显微镜,研究超声外场下7050铝合金半连续铸锭中微观组织的演变规律及溶质元素Zn,Mg和Cu的宏观偏析行为。研究结果表明：熔体超声处理后的铸锭组织变得细小,混晶减少,溶质元素的宏观偏析程度得到弱化,且随着超声功率的增大,溶质元素分布更加均衡,在240 W超声功率作用下,Zn,Mg和Cu的偏析比由未加超声时的1.243,1.158和1.190分别降低为1.086,1.098和1.110;超声外场的引入使得液穴变浅,由铸锭收缩引起的溶质元素在枝晶间的横向流动作用减弱;晶粒的有效细化导致液固两相的相对运动速度减弱;溶质原子的扩散程度得到强化是超声弱化偏析的主要原因。

英文摘要：

The macrosegregation behavior of Zn,Mg,Cu solute elements and evolution of microstructure in 7050 aluminum alloy ingots produced by semi-continuous casting process in the ultrasonic filed was investigated using SPECTRO？MAXx and Leica optic microscopy.The results show that microstructure refines,duplex grains structure consisting of coarse-cell and fine-cell dendritic grains decrease,and so does the segregation grade of solute elements when alloy melt is treated by ultrasonic vibration.With the increase of ultrasound power,distribution of solute elements is harmonious.When the ultrasonic power is from 0 to 240 W,the segregation ratio of Zn,Mg,Cu decreases from 1.243,1.158 and 1.190 to 1.086,1.098 and 1.110,respectively.The sump height decreases in ultrasonic field,the shrinkage-induced flow of enriched solute among dendrite structure decreases,the velocities of the solid and liquid phases in mushy zone decrease due to microstructure refining,and the diffusion of solute atoms increases,which are the main reasons for suppressing macro-segregation