第一性原理研究Al-Cu-Li合金中T1相的腐蚀机理  

Corrosion mechanism of T1 phase in Al-Cu-Li alloy:First-principles calculations

作　　者：孔敏 吴静静 韩天茹[1,2] 唐鑫 Kong Min;Wu Jing-Jing;Han Tian-Ru;Tang Xin(Key Lab of New Processing Technology for Nonferrous Metal&Materials,Ministry of Education,Guilin University of Technology,Guilin 541004,China;College of Material Science and Engineering,Guilin University of Technology,Guilin 541004,China)

机构地区：[1]桂林理工大学,有色金属及材料加工新技术教育部重点实验室,桂林541004 [2]桂林理工大学材料科学与工程学院,桂林541004

出　　处：《物理学报》2020年第2期219-226,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11364009);广西科技重大专项(批准号:AA17129005)资助的课题~~

摘　　要：利用密度泛函理论的第一性原理,讨论Al-Cu-Li合金中主要析出相T1相(Al6Cu4Li3)的表面性质,计算不同终结面的表面能和表面电子功函数,并探讨应力作用和常见合金元素对Al/T1界面的影响.结果表明:T1相的表面能与表面的原子排列有关,不同的表面通过应变释放重构,进而获得不同的表面能.表面电子功函数则与表面原子种类有关,由于Li的电负性最小,含Li原子的表面通常有较低的电子功函数,进而降低材料的耐蚀性.此外,在应力作用下,T1相一些表面的电子功函数变化与纯金属是相反的.压应力下T1相电子功函数降低,材料更加容易被腐蚀;张应力下T1相功函数增加,材料更加耐腐蚀.同时,通过计算Al/T1界面中Ag,Zn和Mg 3种合金元素的替位能,可以发现,这3种元素都有利于降低界面能,且Ag的作用最明显.First principle calculations in the framework of density functional theory are performed to calculate the T1 phase(Al6 Cu4 Li3),which is the main precipitation in Al-Cu-Li alloy.In this paper,the surface energy values and surface electron work functions of different termination surfaces in T1 phase are calculated.Meanwhile,the effects of stress and common alloying elements on the T1 phase are also discussed.There are 10 different termination surfaces for T1 phase.The surface energy varies between 0.59 and 1.28 J·m–2.It is found that the surface energy is dependent on the atomic configuration of the surface.The relaxation of the surficial atoms leads to low surface energy.For work function,it is controlled by the surficial atomic species.When a surface contains Li atoms,low work function is expected,which can be attributed to the low electronegativity of Li atom.The(010)T1 surface with Li termination has a minimum work function,3.40 e V.In addition,as is different from pure metal,work function of some T1 surfaces shows unique behavior under stress state.The(010)T1 surface with Al and Cu termination has an increasing work function under the action of tensile strain.In fact,tensile strain induces the first and second surface layer to merge,which can improve the surface electronic density and raise work function.As a result,the corrosion resistance can be enhanced.Finally,the effect of alloying elements on the precipitation of T1 phase is studied.Al(111)/T1(010)interface is built and the substitution energy of Mg,Zn and Ag are calculated.Comparing with Mg and Zn atom,the energy of Ag atom to substitute the interfacial one is low,meaning that Ag can relax the strain in the interface.Ag atom has the closest atomic radius to Al atom,and the same chemical valence as Li atom.Therefore,Ag atom is more likely to promote the precipitation of T1 phase,which is also in agreement with the experimental result.

关 键 词：AL-CU-LI合金 T1相 电子功函数 

分 类 号：TG146.21[一般工业技术—材料科学与工程] O469[金属学及工艺—金属材料]