Structure-controlled slow dynamics in Al−Mg melts

Al-Mg熔体中结构控制的慢动力学

Molecular dynamics simulation was employed to investigate the dynamical and structural properties of Al−Mg melts with the Al concentration systematically changed.The results show that the viscosity of Al67Mg33 abnormally surpasses that of Al85Mg15 below 550 K,inconsistent with the tendency at high temperatures.The evolution of the icosahedral order population is found to account for this dynamic behavior.Structural analysis shows a preferred bonding between Al and Mg atoms in the nearest neighbor shells,while a repelling tendency between them in the second shells,leading to the prepeak emergence in the partial static structure factors.The formation of icosahedral clusters is constrained in the Al-rich compositions because of the lack of sufficient Mg atoms to stabilize the clusters geometrically.These results demonstrate the structural consequence through the interplay between geometric packing and chemical interaction.These findings are crucial to understanding the structure−dynamic properties in Al−Mg melts.

采用分子动力学模拟方法研究了Al成分变化的Al-Mg熔体的动力学和结构特性。研究结果表明:在温度低于550 K时,Al67Mg33的黏度异常地超越了Al85Mg15的黏度,这与高温下的趋势不一致。二十面体有序结构的演变是导致这种异常动力学行为的原因。结构分析显示:Al和Mg原子在最近邻壳层中表现出优先键合,而在第二近邻壳层中表现出排斥趋势,导致部分静态结构因子中出现预峰;由于缺少足够的Mg原子来稳定二十面体团簇,二十面体团簇的形成在富Al熔体中被抑制。该结果展示了由几何密堆与化学作用之间相互影响所导致的结构演变行为。这些发现对于理解Al-Mg熔体的结构-动力学性质具有重要意义。