Effect of frequency and intensity of rotating magneticfield on the microstructures of Pb-Sn alloys  

作　　者：CHEN Zhao CHEN ChangLe WEN XiaoLi ZHU JianHua GAO WenShuai 

机构地区：[1]Shaanxi Key Laboratory of Condensed Matter Structures and Properties, School of Science, Northwestern Polytechnical University, Xi'an 710072, China

出　　处：《Chinese Science Bulletin》2008年第17期2575-2581,共7页

基　　金：the National Natural Science Foundation of China (Grant Nos. 50331040 and 60171034)

摘　　要：The solidification microstructures of Pb-45% Sn hypoeutectic and Pb-85%Sn hypereutectic alloys were studied in rotating magnetic field (RMF). A transition of primary phase from dendrite to spherical growth was caused by the RMF, which simultaneously fractured and fined grains. The fracture and refinement increased first and then decreased with the increase in RMF intensity. When magnetic intensity exceeded a critical value, the size of the primary phase became bigger on the contrary. Therefore, there existed an optimum value of magnetic intensity in fracture and refinement of grain. Moreover, the rotating frequency determined the skin depth of magnetic field, and further affected the homogenization of temperature and solute. The rotating frequency and magnetic intensity were key factors affect- ing refinement and uniformity of solidification microstructures. The introduction of RMF not only changed the solidification thermodynamics, but also led to a reduction in Gibbs free energy associated with the formation of critical crystal nucleus and atom diffusion activation energy, thus enhancing the rate of nucleation.The solidification microstructures of Pb-45% Sn hypoeutectic and Pb-85%Sn hypereutectic alloys were studied in rotating magnetic field （RMF）. A transition of primary phase from dendrite to spherical growth was caused by the RMF, which simultaneously fractured and fined grains. The fracture and refinement increased first and then decreased with the increase in RMF intensity. When magnetic intensity exceeded a critical value, the size of the primary phase became bigger on the contrary. Therefore, there existed an optimum value of magnetic intensity in fracture and refinement of grain. Moreover, the rotating frequency determined the skin depth of magnetic field, and further affected the homogenization of temperature and solute. The rotating frequency and magnetic intensity were key factors affecting refinement and uniformity of solidification microstructures. The introduction of RMF not only changed the solidification thermodynamics, but also led to a reduction in Gibbs free energy associated with the formation of critical crystal nucleus and atom diffusion activation energy, thus enhancing the rate of nucleation.

关 键 词：铅锡合金 旋转磁场 磁场强度 磁场频率 微观结构 

分 类 号：TG146.1[一般工业技术—材料科学与工程]