Study of the structure of molten Fe-Si alloys by X-ray diffraction

The structures of 14 molten Fe-Si alloys were studied at 1550 V by a theta-theta X-ray diffractometor. The alloys with a composition interval of about 10%Si (atomic fraction) including some intermetallic compounds. The analysis on the experimental data employed the following parameters: the height, position and half-width of the first peak of the structure factor, the first peak position of the pair correlation function, the first peak shape of the radial distribution function and the coordination number etc.. The results show that the structure behavior of molten Fe-Si alloys along the whole composition range could be divided into four intervals which are indicated by 5 borders Of Fe, Fe0.754Si0.246, Fe0.50Si0.50, Fe-0.Si-282(0.718) and pure Si. Distinct structural change was observed across the borders. The liquid structure of Fe0.50Si0.50 alloy inherited the structure of intermetallic compound FeSi to some extent. Covalent bonding between Si-Si atoms was speculated to exist in alloys with Si content higher than 50.0%. Furthermore, the existence of prepeak in the structure factors of some Fe-Si alloys marked the medium-range order in such alloys. Some models and results by other researchers were also discussed.