铝合金表面脉冲电磁场对半连续铸造晶粒的细化  

Refining of a DC-casting aluminum alloy structure using surface electromagnetic pulsing

作　　者：白庆伟 麻永林[1] 邢淑清[1] 冯艳飞[1] 鲍鑫宇[1] 于文霞 

机构地区：[1]内蒙古科技大学材料与冶金学院,包头014010

出　　处：《工程科学学报》2017年第12期1828-1834,共7页Chinese Journal of Engineering

基　　金：国家自然科学基金资助项目(51044002);科技部国际合作资助项目(2010DFB70630)

摘　　要：采用一种新型熔体表面脉冲电磁技术对7A04铝合金半连续铸造凝固组织细化处理,分析脉冲电磁场对凝固组织及性能的影响.引入势能的观点,探讨脉冲磁能作用下的晶体形核动力学及初生晶核运动形式.结果表明,经表面脉冲电磁场处理后,凝固组织由晶粒尺寸粗大的玫瑰结构转变为细小且圆整的球状结构,铸锭心部及边部晶粒尺寸分别下降22.7%和14.2%,强度、塑性均有提高.动力学分析认为,脉冲电磁能降低体系形核所需的临界吉布斯自由能是增加形核率的重要原因,同时可导致初生α-Al运动的势能增加,促使初生α-Al颗粒优先到达稳定位置.A new technique termed surface electromagnetic pulse refining was developed for improving the solidified structure of a7 A04 aluminum alloy DC-casting. The effect of the pulsed electromagnetic field on the solidified microstructure and properties of the alloy was investigated. From the viewpoint of potential energy,the dynamics of forming nucleus and the grain motion were theoretically predicted based on the concepts of the action of the pulsed electromagnetic energy on the melt or particles. The experimental results indicate that the solidified structures are modified by the electromagnetic pulse from rose-like structures to globular structures with a fine grain size. The grain size in the edge zone and central zone of the billet is decreased by 22. 7% and 14. 2%,respectively,and the strength and plasticity of the alloy are also increased. The grain refinement can be explained by the nucleation rate increases,because the electromagnetic energy helps to decrease the critical Gibbs free energy of the system. In addition,the electromagnetic pulse appears to increase potential energy of the primary α-Al,which quickly attains a steady state in the melt.

关 键 词：晶粒细化 脉冲电磁场 形核率 磁势能 

分 类 号：TF821[冶金工程—有色金属冶金]