Nucleation and growth mechanisms of γ〞 phase with single-unit-cell height in Mg-RE-Zn(Ag) series alloys: a first-principles study

作     者：Junyuan Bai Hongbo Xie Xueyong Pang Guo Yuan Lei Wang Yuping Ren Gaowu Qin Junyuan Bai;Hongbo Xie;Xueyong Pang;Guo Yuan;Lei Wang;Yuping Ren;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 State Key Laboratory of Rolling and AutomationNortheastern UniversityShenyang 110819China Research Centre 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：2021年第79卷第20期

页      面：133-140页

核心收录：

学科分类：08[工学] 0817[工学-化学工程与技术] 0806[工学-冶金工程] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学] 0703[理学-化学] 0802[工学-机械工程] 0801[工学-力学（可授工学、理学学位）] 0702[理学-物理学] 

基　　金：This work was financially supported by the National Key Research and Development Program of China(No.2016YFB0701202) the Fundamental Research Funds for the Central Universities(Nos.N2007011,N160208001) 111Project(No.B20029)。 

主　　题：Thermal stability Mg-RE-Zn(Ag)series alloys γ"phase First-principles Ledge-thickening 

摘      要：The highly thermal stability precipitates strengthen creep resistance for alloys,which require precipitates to resist coarsen at elevated temperature.In the Mg-RE-Zn(Ag)series alloys,the key strengthening phase-γphase,remains its single-unit-cell height throughout aging process.The origin of such extremely thermal stability ofγphase is still unclear.By using the first-principles calculations,it is found that the formation ofγphase introduces compressive strain to its surroundingα-Mg lattice and simultaneously alter charge distribution ofα-Mg lattice near theα-Mg/γhetero-interface.These two variations overα-Mg lattice lead to lower vacancy formation energies and migration energy barriers for solute atoms near theα-Mg/γhetero-interface in comparison with that of bulk condition.Consequently,the variations facilitate rapid diffusion of solute atoms near theγphase and promote nucleation rate of otherγplates around it.On the basis of ledge-thickening model,the origin of nucleation/growth ofγphase with single-unit-cell height was explained.Thermodynamically and kinetically,the solute atoms are not apt to migrate into the nearest basal plane adjacent to theγphase.Moreover,the lower aging temperature(~200℃)and almost completely coherentα-Mg/γhetero-interface lead to the ledges are extremely hard to nucleate on the hetero-interface.Therefore,γplates maintain single-unit-cell height throughout aging process.