交流磁场致Al-Fe亚共晶合金熔体热电势变化的研究

Investigation on the Change of Thermoelectric Power of Al-Fe Hypoeutectic Alloy Melt Caused by AC Magnetic Field

研究了不同温度、不同励磁电流、不同磁场频率和不同加载时间条件下,交流磁场对Al-0.99%Fe(质量分数)亚共晶合金熔体热电势差(U)和熔体微观结构的影响。结果表明:交流磁场加载过程中,Al-0.99%Fe亚共晶合金熔体的U逐渐减小,交流磁场撤除后,减小的U经历了快速恢复和缓慢恢复过程。不同温度下,交流磁场对Al-0.99%Fe亚共晶合金熔体U的影响程度不同;随着磁场频率的增大,交流磁场对Al-0.99%Fe亚共晶合金熔体U的影响逐渐减小;随着励磁电流和加载时间的增大,交流磁场对Al-0.99%Fe亚共晶合金熔体U的影响逐渐增大,但存在一个饱和加载时间。交流磁场导致Al-0.99%Fe亚共晶合金熔体的U变化与合金熔体淬火凝固组织中初生a-Al相尺寸变化之间存在相关性,因而可以用U的变化来表征交流磁场对Al-0.99%Fe亚共晶合金熔体微观结构的影响。

A lot of studies have shown that electromagnetic field can significantly refine the metal solidification structure, thus improve the deformation properties and functional performance of metallic materials. However, the mechanism of how electromagnetic field affects melt structure remains unclear, so an intensive study of the effects of electromagnetic field on melt structure is very important for an in-depth understanding of the essence of melt solidification under external electromagnetic field. The effect of alternating current（AC） magnetic field with different exciting currents, magnetic frequencies and loading time on the thermoelectric potential difference（U） and melt microstructure of Al-0.99%Fe（mass fraction）hypoeutectic alloy at different temperatures was investigated in this work. The results showed that AC magnetic field would lead to a decrease in U of liquid Al-0.99%Fe hypoeutectic alloy. When the magneticfield was removed, the decreased thermoelectric potential difference experienced a rapid recovery process and a poor recovery process to increase to the initial value. The influence of AC magnetic field on U was different at different temperatures. With the increase of the magnetic frequency, the influence of AC magnetic field on U decreased. And the influence of AC magnetic field on U increased with the increase of the exciting current and loading time, however, there was a saturated loading time. There was a correlation between the change of U of Al-0.99%Fe hypoeutectic alloy and the change of size of the primary a-Al phase caused by AC magnetic field, therefore, the change of thermoelectric potential difference could be used to characterize the effect of AC magnetic field on the microstructure of the alloy melt of Al-0.99%Fe hypoeutectic alloy.