冷速对液态金属Ga凝固过程中微观结构演变影响的模拟研究

采用分子动力学方法对液态金属Ga凝固过程中不同冷却速率对微观结构演变的影响进行了模拟跟踪研究. 运用HA键型指数法和原子成团类型指数法(CTIM)分析了金属原子Ga的成键类型和形成的基本原子团结构. 结果发现，冷却速率对凝固过程中的微观结构起着非常重要的作用. 在以1.0×10¹⁴，1.0×10¹³，1.0×10¹²K/s的速率冷却时，系统形成以与1311，1301键型相关的菱面体结构为主，夹杂着立方体、六角密集等其他团簇结构所构成的非晶态结构；在以1.0×10¹¹K/s的速率冷却时，系统明显发生结晶，其结晶转变温度T_c约为198K，且冷却速率越慢，结晶转变温度T_c越高，形成以与1421键型相关的斜方晶体(经可视化分析确认)为主要构型的晶态结构. 这将为研究液态金属的结晶转变过程提供一种新方法. 关键词： 液态金属Ga 凝固过程 微结构转变 分子动力学模拟

A simulation study for the effects of cooling rate on evolution of microstructures during solidification of liquid metal Ga

A simulation tracing study has been performed for the effects of different cooling rates on the evolution of microstructures during solidification process of liquid metal Ga by means of molecular dynamics method. The bond-types and basic cluster structures of metal Ga have been analyzed by using HA bond-type index method and cluster-type index method. It has been found that the cooling rate plays an important role to the microstructures in the solidification processes. At the cooling rates of 1.0×10¹⁴ K/s, 1.0×10¹³ K/s and 1.0×10¹² K/s, the amorphous structures would be formed in the system with the rhombohedron related to 1311, 1301 bond-types as the main body, and coexist with the fcc, hcp and other structures; at the cooling rate of 1.0×10¹¹K/s, crystallization would take place in the system, the crystalline transition temperature T_c being about 198K, and the lower the cooling rate, the higher the T_c. The crystal would have the orthorhombic structure related to 1421 bond-type(determined by visualized method) as the main body. This gives us a new way for researching the crystalline transition processes of liquid metals.