液态Mg7Zn3合金快速凝固过程中微观结构演变机理的模拟研究

采用分子动力学方法对液态Mg₇Zn₃合金的快速凝固过程进行了模拟研究,并采用双体分布函数、Honeycutt-Andersen键型指数法、原子团类型指数法(CTIM)以及遗传跟踪等方法对凝固过程中团簇结构的形成、演变特性进行了分析.结果表明:在以冷速为1×10¹² K ·s^-1的凝固过程中, Zn-Zn原子之间的相互成键的概率明显增加,形成以1551,1541,1431键型为主的非晶态结构.其特征键型1551随温度变化 关键词： 液态MgZn合金 快速凝固过程 微观结构演变 分子动力学模拟

Simulation study of evolution mechanisms of microstructures during rapid solidification of liquid Mg7Zn3 alloy

A simulation study has been performed for the rapid solidification process of liquid Mg₇Zn₃ alloy by using molecular dynamics method. The pair distribution function g(r) curves, the bond-type index method of Honeycutt-Andersen (H-A), the cluster-type index method and the genetic tracking method have been used to analyze the formation and evolution properties of cluster structures during the solidification process. The results show that the bonding probability between Zn-Zn atoms is increased obviously during the solidification process at cooling rate of 1×10¹² K ·s^-1. The amorphous structures are formed mainly with the 1551, 1541 and 1431 bond-types, and the turning point of the relation curve of the characteristic 1551 bond-type with temperature is corresponding to the glass transition temperature T_g, thus it maybe become a new method to determine T_g. The basic cluster (12 0 12 0) consisting of 1551 bond-type plays a key role in forming amorphous structure, and becomes the main body of the large clusters which are formed by the combination of some middle and small clusters with distinctly different sizes, through mutual competition by unceasing annex and evolution in a seesaw manner (in turn of obtaining and losing).