%A Ronghua CUI, Xinyu WANG, Zhengchao DONG, Chonggui ZHONG
%T First Principles Study on Elastic and Thermodynamic Properties of Mg_{1-}_{x}Zn_{x} Alloys
%0 Journal Article
%D 2017
%J Acta Metall Sin
%R 10.11900/0412.1961.2016.00583
%P 1133-1139
%V 53
%N 9
%U {https://www.ams.org.cn/CN/abstract/article_25595.shtml}
%8 2017-09-11
%X As one of the lightest metal materials in current industrial applications, Mg alloys are being widely used in automotive, aircraft, aerospace and biomedical industries because of their super high strength-to-weight ratio and biodegradability. However, their limited ductility and workability at room temperature have become a bottleneck for many applications. Therefore, it has become critically important to obtain the Mg alloys with improved strength and ductility. On the other hand, Zn is a transition metal element, often applied to improve the mechanical properties. Also it has basic safety for biomedical applications. So the Mg-Zn alloys have attracted considerable attentions in recent years. Extensively investigated experiments indicated that the hardness of Mg-Zn alloys increases with increasing Zn content. However, there are only a few reported works about their mechanical properties and theoretically thermodynamic properties of Mg-Zn alloys. In this work, first-principles investigations have been performed on lattice parameters, elastic properties and thermodynamic properties of hcp Mg and eight kinds of Mg_{1-}_{x}Zn_{x} alloys with different contents of Zn less than 2% (atomic fraction), using the virtual crystal approximation in the frame of the density functional theory and the density functional perturbation theory. The elastic constants of Mg and Mg_{1-}_{x}Zn_{x} alloys with different Zn contents have been investigated by using optimized lattice, and their Young's moduli, Poisson ratios and elastic anisotropies have been analyzed in detail. Also, the thermodynamic properties, including Helmholtz free energies, internal energies, entropy and constant volume heat capacities of these alloys as a function of temperature were discussed. The results show that with increasing Zn content in Mg_{1-}_{x}Zn_{x} alloys, the lattice constants *a* and *c*, the entropy and constant volume heat capacity of Mg_{1-}_{x}Zn_{x} alloy decrease, while the elastic constants, Helmholtz free energy and internal energy of Mg_{1-}_{x}Zn_{x} alloy increase correspondingly. On the other hand, further discussions find that the effects of Zn content on free energy and entropy of Mg_{1-}_{x}Zn_{x} alloy are enhanced and the effect on heat capacity of each alloy at constant volume first increases, then decreases as the temperature rises. In summary, it can be given the conclusions that the high content of Zn in Mg_{1-}_{x}Zn_{x} alloy is beneficial to increasing the hardness and ductility of such Mg_{1-}_{x}Zn_{x} alloy, but decreasing its isotropy.