Abstract: The mediumrange structure order(MRSO) of liquid Al80Fe20 alloy and the evolution of microstructure of the system during the rapid cooling are analyzed by MD simulation. It is found that there exists a prepeak in the smallQ domain of structure factor for all of them, which is considered to be indicative of MRSO in the system. In the equilibrium state(1450 K), the results of simulation are further proofed by that of Xray diffraction experiment. With temperature decreasing, the height of prepeak is increasing gradually, which shows that the size of atomic clusters is getting bigger. By means of pair analysis technique and bond orientational order, we find that there exist a number of icosahedral shortrange units in the system. The minus chemical shortrange order(CSRO) parameter α indicates that there is much stronger CSRO in the liquid system. The second peak of SAlFe(Q)splits much more sharply than those of SAlAl(Q) and SFeFe(Q) at 400 K in FZ partial structure factor, which indicates that the orbit hybridization between Al and Fe atoms plays a more important pole than Al and Fe atoms solely in the ability of forming amorphous. In BT partial structure factor, there is a first peak at 17.5 nm－1 in SCC(Q), indicative of CSRO. And this position is just where a prepeak appearing in the total structure factor. So we think that it is the CSRO that result in the MRSO in the system.

Key words: Al₈₀Fe₂₀ liquid alloy, Rapid solidify, MD simulation, Mediumrange order, Structure factors