中文摘要：

通过在常规半连续铸造过程中施加低频电磁场的方法制备了直径为162mm的7050铝合金铸锭,研究了电磁场对铸锭铸态组织的影响。结果表明,低频电磁场对7050铝合金铸态晶粒尺寸和组织形貌具有显著的影响。施加磁场后铸锭组织变得非常均匀、细小,平均晶粒尺寸由230μm细化至42μm左右,晶粒形貌由粗大枝晶转变等轴晶。电磁场频率和强度对晶粒细化具有重要的影响。对于低频电磁铸造162mm的7050铝合金铸锭,最佳电磁场参数：电磁场频率为25Hz,磁场强度为12800～16000At。

英文摘要：

7050 aluminum alloy ingots with 162 mm in diameter were prepared by direct chill（DC） casting process with applying a low frequency electromagnetic field,and effects of electromagnetic field on the as-cast microstructure were investigated.The experimental results show that low frequency electromagnetic field has a significant effect on both grain size and morphology of grains in 7050 alloy.The average grain size is evidently reduced from 230 μm to about 42 μm,and the morphology is transformed from coarse dendrite to fine spherical euiaxed structure.The electromagnetic field frequency and intensity play very important roles in refining the grain size.The optimum processing parameters for casting 7050 alloy ingot with 162 mm are presented as follows：electromagnetic field frequency of 25 Hz and electromagnetic field intensity of 12 800～16 000 At.