低频电磁场对半连续铸造Al-Mg-Si-Cu合金显微组织的影响

Effect of Low Frequency Electromagnetic Field on Microstructure of DC Casting Al-Mg-Si-Cu Aluminum Alloy Ingots

采用低频电磁场半连续铸造工艺制备Al-Mg-Si-Cu铝合金铸锭,研究了低频电磁场对Al-Mg-Si-Cu铝合金铸锭组织的影响。结果表明,施加低频电磁场可以细化Al-Mg-Si-Cu铝合金铸锭的晶粒组织,减轻晶内元素的偏析程度。与常规半连续铸造相比,施加频率为20 Hz、电流为120 A的交变电磁场后,铸锭中的等轴晶组织增多,枝晶状组织减少,晶粒尺寸变得更加细小,铸锭边部和中心平均晶粒尺寸由常规半连续铸造的170和259μm分别降至133和187μm,同时有利于提高溶质元素在晶内的分布,很大程度上减轻了溶质元素的偏析。此外,低频电磁场的电磁振荡使得液穴内部温度场和流动场更趋均匀,溶质元素分配系数增大,结晶区间变小,抑制了树枝晶的生长,促进了Al-Mg-Si-Cu合金半连续铸锭中非枝晶组织的形成和溶质元素的强制固溶,并且抑制了溶质元素的偏析。

The Al-Mg-Si-Cu aluminum alloy ingots were prepared by using low frequency electromagnetic field semi-continuous casting process. The effect of low frequency electromagnetic field on the microstructure of Al-Mg-Si-Cu alloy ingots was studied. The results show that the grain structure of Al-Mg-Si-Cu alloy ingots can be refined by applying low frequency electromagnetic field, and the segregation degree of the elements inside the ingots can be reduced.Compared with conventional semicontinuous casting, the applied frequency is 20 Hz, current is 120 A alternating electromagnetic field, the isometric microstructure increase in ingot casting, dendritic structure, grain size more small, ingot casting side and the center of the average grain size by regular semi-continuous casting of 170 and 259 μm down to 133 and 187 μm respectively, at the same time to improve the distribution of solute elements in the intracrystalline, greatly reduce the segregation of solute elements. In addition, the low frequency electromagnetic field in the electromagnetic oscillation makes liquid hole inner temperature field and flow field more uniformly, solute elements distribution coefficient increases, crystallization range smaller, inhibits the growth of dendrites, promoted the Al-Mg-Si-Cu alloy semi-continuous casting non-dendritic structure formation and forced solid solution of solute elements, and suppress the segregation of solute elements.