液态Al80Fe20在快速冷却中的MD模拟

通过Tight binding (TB)势的分子动力学模拟分析了Al80Fe20合金熔体的中程有序结构以及快速凝固过程中体系微观结构的演变规律，发现在倒空间，其结构因子的小角部分都出现了一个预峰.在平衡态（1450 K），模拟结果得到了X射线衍射实验的进一步印证，这被认为是体系中存在中程有序的标志.随着温度的降低，预峰的高度逐渐增大，说明体系中原子团簇尺寸越来越大.通过运用键对分析技术和键取向序参数，发现体系中存在着大量的二十面体短程有序单元.在对平衡态化学短程序参数α的计算过程中，得到了负值的α，证实了熔体中存在着较强的化学序.在FZ偏结构因子中， SAl Fe(Q)在400 K的第二峰较之SAl Al(Q)和SFe Fe(Q)发生了更为明显的劈裂，表明在非晶形成能力方面， Al、Fe元素之间的轨道杂化作用比Al元素或Fe元素单独作用要强.从BT偏结构因子中我们也发现，表征化学序的SCC(Q)在17.5 nm－1左右处出现了第一峰，而这个峰位恰是总结构因子中出现预峰的峰位.因此可推断，正是体系中的化学序导致了中程有序结构的产生.

MD Simulation of Liquid Al80Fe20 Alloy during Rapid Cooling

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.