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利用直接水冷半连续(常规DC)铸造工艺和低频电磁铸造(LFEC)工艺分别制备了Al-4.5%Cu(质量分数)合金铸锭.测量了常规DC铸造和LFEC过程中的温度曲线,研究了低频电磁场条件下的铸锭微观组织变化和Cu元素的微观偏析.通过金相观察发现,在低频电磁场作用下,α-Al和θ相的共晶组织变得细小,其面积分数明显减小.利用电子探针测量结果绘制Cu元素成分曲线,发现在凝圈的最初过渡区,Cu元素的成分曲线在低频电磁场作用下升高,α-Al中Cu元素含量增加.通过计算得到Cu元素的有效分配系数k_e,发现在最初过渡区k_e线性增大到1.LFEC工艺使得Cu元素的k_e变大,并且随着电流强度的增强这一趋势愈发明显.由于低频电磁场加速了凝固前沿的冷却速度,使更多的Cu原子固溶在α-Al中,Cu元素在铸锭中的微观偏析得到了改善.
Al-4.5% Cu (mass fraction) alloy ingots were fabricated by direct water-cooled semi-continuous (conventional DC) and LFEC techniques respectively.The temperature curves during conventional DC casting and LFEC were measured, In the low frequency electromagnetic field, the microstructure of the ingot and the micro segregation of Cu element were observed. The metallographic observation showed that the eutectic structure of α-Al and θ phase became small and the area fraction decreased obviously under low frequency electromagnetic field. The curve of Cu elemental composition was plotted by electron probe measurements. It was found that the Cu elemental composition curve increased under the action of low frequency electromagnetic field and the content of Cu element in α-Al increased in the initial transition zone of the coagulation ring. Distribution coefficient k_e and found that the initial transition k_e linear increase to 1.LFEC process makes the Cu element k_e larger, and with the current intensity of this trend is more obvious.As the low-frequency electromagnetic field accelerated the solidification front cooling rate , So that more Cu atoms in solid solution in the α-Al, Cu element in the ingot microstructure segregation has been improved.