The Effect of Fe Content on the Solidification Pathway, Microstructure and Thermal Conductivity of Hypoeutectic Al-Si Alloys

In the present study, the solidification pathway, microstructure and thermal conductivity of Fe-rich Al-x Si (x = 5, 7, 9, wt%, the same below) alloys were systematically investigated. The results showed that the thermal conductivity was firstly improved and then decreased with Fe content increasing. The improvement and decreasing rate of thermal conductivity was related to the Si content. The change of thermal conductivity was closely related to the change of microstructure and solidification pathway. The addition of Fe element resulted to the precipitation of ternary beta (Al5SiFe) phase (beta(T)) and binary beta phase (beta(B)). The precipitation of beta(T) was benefited to improve the thermal conductivity. On the contrast, the precipitation of beta(B) was prone to deteriorate the thermal conductivity. The precipitation amount of beta(T) phase and beta(B) phase was related to the critical value of Fe content (Fe-crit). The calculation results showed that the Fe-crit of Al-x Si alloys was about 0.20% (5% Si), 0.29% (7% Si) and 0.38% (9% Si), respectively. When the Fe content was less critical value (Fe-crit), the precipitation amount of beta(T) phase was increased by Fe increasing. Furthermore, when the Fe content was more than Fe-crit, the precipitation amount of beta(T) phase was changed slightly, and the precipitation amount of beta(B) phase continued to increase with Fe content increasing.

Automated summary

The present study systematically investigated the solidification pathway, microstructure, and thermal conductivity of Fe-rich Al-x Si alloys. It was found that the thermal conductivity initially improved and then decreased with increasing Fe content, with the rate depending on the Si content. The addition of Fe led to the precipitation of different phases, which had varying effects on thermal conductivity.