低频电磁场对过共晶铝硅合金组织的影响

Effect of Low-Frequency Electromagnetic Field on Microstructure of Hypereutectic Al-Si Alloys

采用低频电磁半连续铸造技术制备Al-19.2%Si合金铸锭,利用电子光学显微镜对铸锭的显微组织进行分析比较,研究了电磁场强度和频率对初生硅颗粒形貌的影响;利用测温技术对合金的凝固过程进行监测,研究低频电磁场对凝固前沿温度场的影响.实验结果表明:与普通DC铸造相比,采用低频电磁半连续铸造可以明显改变液穴中熔体的温度场,使其温度显著下降,温度分布均匀,液穴降低,初生硅颗粒得到有效细化;改变外加电磁场条件,随着电磁场强度的增加,初生硅颗粒细化;随着电磁场频率的增加初生硅颗粒逐渐变大.在本实验条件下,外加电磁场条件为15 Hz,12000At时,初生硅颗粒最为细小.

The influence of low-frequency electromagnetic field on microstructure and morphology of primary Si particles of Al-19.2%Si alloy ingot specimens prepared by semicontinuous casting process was investigated with electronic optical microscopy, where the specimens were taken from different parts of the cast to which different electromagnetic fields are applied. The results showed that when applying the low-frequency electromagnetic field to the casting process the microstructure can be improved obviously with the sump in melt decreased due to more uniform temperature distribution in comparison with DC casting, especially efficient refinement of primary Si particles along with the increasing magnetic field intensity is shown. However, the increasing frequency of electromagnetic field will result in bigger primary Si particle size. In this experiment, the finest size of primary Si particles is found at 15 Hz under 12 000 At.