Anomalous crystal structure of γ" phase in the Mg-RE-Zn(Ag) series alloys:Causality clarified by ab initio study

作     者：Junyuan Bai Xueyong Pang Xiangying Meng Hongbo Xie Hucheng Pan Yuping Ren Min Jiang Gaowu Qin Junyuan Bai;Xueyong Pang;Xiangying Meng;Hongbo Xie;Hucheng Pan;Yuping Ren;Min Jiang;Gaowu Qin

作者机构：Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education)School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China Research Center for Metallic WiresNortheastern UniversityShenyang 110819China 

出 版 物：《Journal of Materials Science & Technology》 (材料科学技术（英文版）)

年 卷 期：2020年第36卷第1期

页      面：167-175页

核心收录：

学科分类：08[工学] 080502[工学-材料学] 0805[工学-材料科学与工程（可授工学、理学学位）] 

基　　金：supported by the National Key Research and Development Program of China(No.2016YFB0701202) the Fundamental Research Funds for the Central Universities(No.N160208001) the National Natural Science Foundation of China(Nos.51525101,51501032,and U1610253) 

主　　题：First-principles γ"phase Mg-RE-based series alloys Crystal structure Mechanical-properties 

摘      要：The crystal structure of the single-unit-cell thickness γ phase,as a key strengthening phase in Mg-REZn(Ag) series alloys,has been extensively studied,and several structural models have been proposed in the past two ***,these reported models,and even the lattice constants at the same proposed structure,are scattered severely,which has led to considerable confusion and not available for further mechanical property simulation and prediction of Mg alloys containing this *** this study,by using first-principles calculations,the crystal structure of y phase is clarified,resolving the discrepancies among different experiments,and its intrinsic mechanical properties have also been studied for the first *** is verified that the γ phase contains quasi-five atomic layers,instead of the previously reported tri-layer,and surprisingly,its crystal structure has many variants,which would change with the alloy ***,with the help of the simulated selected area electron diffraction(SAED) patterns,it is found that the atoms in the central layer remain partially ordered distribution,and this ordered extent primarily depends on the atomic ratio of RE:Zn(Ag) and the solute content in an *** is,the ordered extent increases with decreasing the atomic ratio of RE:Zn(Ag) and/or increasing solute content of alloy,and vice *** and Zn dissolved in the γ phase would produce almost opposed mechanical anisotropy for the γ phase under the identical crystal structure,and the addition of Ag shows more efficient on increasing the shear modulus of γ phase.