电磁搅拌对含Bi过共晶Al-Si合金组织的影响

Effects of Electromagnetic Stirring On Microstructure of Bi-Containing Hypereutectic Al-Si Alloy

通过在含Bi的过共晶Al-Si合金中施加旋转磁场进行电磁搅拌,采用金相显微镜和扫描电镜等对其显微组织进行观察,并对电磁搅拌和Bi相的作用机理进行了分析探讨。结果表明,对含Bi的过共晶Al-Si合金进行电磁搅拌后,初生Si数量大幅减少,只有很少的以细小块状存在,针状共晶Si相数量增加,同时出现了树枝状初生α-Al相。随着施加旋转磁场电流度的提高,共晶Si相形状的转变方式为粗大针状→细针状→粗大针状;同时,电磁搅拌能够改变Bi相局部聚集的不均匀分布状态。随着磁场电流的提高,Bi的分布状态按照大块状→短棒状→球状→小圆球状变化,由局部聚集转变为均匀分布。

Effects of electromagnetic stirring on microstructure of Bi-containing hypereutectic Al-Si alloy were observed by OM (optical microscope) and SEM (scanning electron microscope), and effect mechanism of electromagnetic stirring and Bi phase was analyzed. The results show that primary Si phase is greatly decreased in the presence of a little fine bulky phase, and acicular eutectic Si phase is increased with the occurrence of primary α-Al dendrite phase in electromagnetic stirred Bi-containing hypereutectic Al-Si alloy. With increasing in stirring velocity, morphology of eutectic Si phase is transformed from coarse acicular structure to fine acicular one to coarse acicular one. Meanwhile, segregation of Bi in the alloy can be obviously improved by electromagnetic stirring. With increasing in stirring velocity, distribution morphology of the Bi in the alloy is converted from bulky structure to short-rod one to spherical one to fine spherical one, tending to uniform distribution.