Influence of minor Co on the formation of intermetallic phases in the Al91Fe7Si2 alloy

The performance of Al-Fe-Si alloy is predominantly controlled by type and morphology of the formed intermetallic compounds (IMCs). Here the influence of minor addition of Co on the microstructural formation of Al91Fe7Si2 alloy was explored in a wide cooling rate range of 1-100 K/s. According to the results of microstructure analysis, it is found that both θ-AlFe(Si) phase and α-AlFeSi phase exist in the Al91Fe7Si2 alloy, while the θ-AlFe(SiCo) phase dominates the microstructure of Al89Fe7Si2Co2 alloy solidified with all explored cooling rates. This observation indicates that the addition of Co improves stability of the θ-AlFe(Si) IMCs in the Al91Fe7Si2 alloy. Furthermore, the formation of the θ-AlFe(SiCo) phase in the explored Al89Fe7Si2Co2 alloy is discussed in a solution-strengthening mechanism.