Effect of frequency and intensity of rotating magnetic field on the microstructures of Pb-Sn alloys
Effect of frequency and intensity of rotating magnetic field on the microstructures of Pb-Sn alloys
复制标题
DOI：
10.1007/s11434-008-0368-4
复制
发表时间：
2008-08
影响因子：
--
通讯作者：
Zhao Chen;Changle Chen;X. Wen;Jianhua Zhu;Wenshuai Gao
中科院分区：
文献类型：
--
作者：
Zhao Chen;Changle Chen;X. Wen;Jianhua Zhu;Wenshuai Gao
研究了Pb-45%Sn亚共晶和Pb-85%Sn过共晶合金在旋转磁场（RMF）下的凝固组织。 RMF 引起初生相从枝晶向球状生长的转变，同时断裂和细化晶粒。随着RMF强度的增加，断裂和细化先增加后减少。当磁场强度超过某一临界值时，初生相的尺寸反而变大。因此，断裂和细化晶粒时存在一个最佳磁场强度值。此外，旋转频率决定了磁场的趋肤深度，进而影响温度和溶质的均匀化。旋转频率和磁场强度是影响凝固组织细化和均匀性的关键因素。 RMF的引入不仅改变了凝固热力学，而且导致与临界晶核形成相关的吉布斯自由能和原子扩散活化能降低，从而提高了成核速率。
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.