Zn-Mg合金的结构分析和Zn-Mg扩散体系的物相分布

摘要

Molecular dynamics (MD) simulations usually analyze the structure of a phase by radial distribution function (RDF), the Honeycutt-Anderson (HA) bond pair analysis, and the cluster-type index method (CTIM). In this paper, we improve CTIM to allow the characterization of more kinds of crystal structure besides bccfcchcpnon-crystal based on the theory of CTIM. The crystal structures of Zn-Mg alloys have been characterized and the phase distribution of the Zn-Mg diffusion system has been analyzed by CTIM. The results show that the CTIM integers can reveal differences between the Mg21Zn25, MgZn2, and Mg2Zn11 structures, and similarities between the Mg4Zn7 and MgZn2 structures. Using a two-step simulation on the Zn-Mg diffusion system, fcc and hep crystals occur at both extremes of the system and there are many non-crystal phases in the middle of the system. In addition, our results show that the interface structure of fee and hep crystals on the Zn side is mainly Zn12-C.%分子动力学(MD)模拟常采用径向分布函数(RDF)、Honeycutt-Anderson (HA)键型指数法、原子团类型指数法(CTIM)表征物相的微观结构.本文依据CTIM理论,对CTIM进一步发展,使CTIM不仅能够表征bccfcchcp非晶体,也能表征其它晶系的晶体结构.本文采用CTIM完成Zn-Mg合金标准晶体的结构表征和Zn-Mg扩散体系物相分布的分析.结果表明:合金组元的CTIM指数不仅反映了Mg21Zn25、MgZn2、Mg2Zn11晶体结构的差异,也说明了Mg4Zn7、MgZn2晶体结构十分相近.Zn-Mg扩散体系两步法模拟后,体系两端交替分布着hcp与fcc结构;体系中部形成大量的非晶体;Zn原子端交替分布着hcp与fcc结构的界面区域主要是Zn12-C类原子.