Zn-Mg合金的结构分析和Zn-Mg扩散体系的物相分布

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bcc\fcc\hcp\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.

Analysis of Zn-Mg Alloy Structure and Phases Distribution of Zn-Mg Diffusion System

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 bcc\fcc\hcp\non-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 hcp 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 fcc and hcp crystals on the Zn side is mainly Zn12-C.