——直径0.2m锭坯的铸态组织
(东北大学 材料电磁过程研究教育部重点实验室， 沈阳 110004)
摘 要: 采用低频电磁铸造技术， 半连续铸造制备了直径为0.2m的7A60超高强铝合金锭坯。 研究了铸锭表面质量和内裂纹发生情况， 考察了电磁场频率和强度对铸态组织的影响。结果表明： 低频电磁场可消除锭坯裂纹， 改善其表面质量。 在低频电磁场作用下， 半连续铸造组织得到显著细化， 铸锭边部和中间部位的晶粒大小差别减小， 其平均晶粒尺寸分别为30μm和45μm。 适当降低电磁场频率和增加强度有利于获得细小均匀的等轴晶组织，铸造组织最佳的电磁场频率为25Hz， 安匝数为18000A·turn。
关键字: 低频; 电磁铸造; 微观组织; 细化; Al-Zn-Mg-Cu-Zr
low frequency electromagnetic cast（Ⅰ）——as-cast structures of billets with diameter of 0.2m
（Key Laboratory of Electromagnetic Processing of Materials for Ministry of Education, Northeastern University,
Shenyang 110004， China）
Abstract:Under the low frequency electromagnetic field, a super-high strength 7A60 Al alloy was semi-continuously cast into billets with diameter of 0.2m. The surface properties, inner cracks of billets and the effect of electromagnetic frequency and intensity on as-cast microstructures were investigated. The microstructures of 7A60 Al alloy cast under low frequency electromagnetic field are fine, uniform and equiaxed, the difference of the microstructures between the border and center of the billet is small, their average sizes are 30 and 45μm, respectively. The decrease of electromagnetic frequency and increase of intensity are helpful for obtaining fine, uniform and equiaxed as-cast microstructures. The optimum electromagnetic parameters are that the frequency is 25Hz and the number of ampere turns is 18000A·turn.
Key words: low frequency; electromagnetic cast; microstructure; refinement; Al-Zn-Mg-Cu-Zr
