点缺陷浓度对非化学计量比L1_2型结构的A1_3Sc弹性性能的影响  

Effects of point defect concentrations on elastic properties of off-stoichiometric L1_2-type A1_3Sc

作　　者：张朝民[1,2] 江勇[2,3] 尹登峰[1,2,3] 陶辉锦[2,3] 孙顺平[4] 姚建刚[1] 

机构地区：[1]烟台南山学院工学院数理教学部,龙口265713 [2]中南大学材料科学与工程学院,长沙410083 [3]中南大学,教育部有色金属材料重点实验室,长沙410083 [4]江苏理工学院材料工程学院,常州213001

出　　处：《物理学报》2016年第7期238-249,共12页Acta Physica Sinica

基　　金：山东省科技发展计划(批准号:2014GGX102006);山东省高等学校科技计划(批准号:J14LJ51)资助的课题~~

摘　　要：采用密度泛函理论与Wagner-Schottky热力学模型计算了金属间化合物L1_2-A1_3Sc中点缺陷浓度与温度、成分间的关系.结果表明:在考察的温度区间(T=300—1200 K),理想化学计量比L1_2-A1_3Sc中的点缺陷主要为Al空位和Sc空位,且缺陷浓度较低(在1200 K时仅约为10^(-6)).当L1_2-A1_3Sc偏离化学计量比成分时,富Al成分端的点缺陷主要为Al反位与Sc空位,且两种缺陷的浓度相当;富Sc成分端的点缺陷则主要为Sc反位.利用超胞模型进一步计算了含点缺陷L1_2-A1_3Sc晶体的弹性常数,并计算预测了点缺陷形式和浓度对其弹性性能的影响.结果表明:在理想化学计量比成分附近,点缺陷的引入均会降低非化学计量比L1_2-Al_3Sc晶体的杨氏、剪切和体积弹性模量,增加非化学计量比L1_2-Al_3Sc弹性性能的各向异性,但是对其脆-韧性的影响不大.Elastic properties and phase stabilities of L1_2-A1_3 Sc precipitate phase in Al-Sc alloys have been topics of experimental and theoretical research over the past years. However, these properties of off-stoichiometric L1_2-A1_3 Sc have not been investigated. Firstly, in combination with Wagner-Schottky model, the first-principles total energy calculations based on density functional theory are performed to study point defect concentrations of intermetallic L1_2-A1_3 Sc each as a function of temperature and alloy composition. We calculate the point defect formation enthalpies and plot the point defect density curves of stoichiometric and off-stoichiometric L1_2-A1_3 Sc at 1000 K. The results show that within the whole temperature range（300–1200 K）, Al and Sc vacancies dominate on stoichiometric L1_2-A1_3 Sc but with low concentrations（~10^（-6） even at 1200 K）; on the Al-rich side of off-stoichiometric L1_2-A1_3 Sc, the Al anti-site and the Sc vacancy concentrations dominate, and their concentrations are comparable, however, on Sc-rich side of off-stoichiometric L1_2-A1_3 Sc, the Sc anti-site defect dominates. Furthermore, the lattice constants and the elastic constants of stoichiometric and off-stoichiometric L1_2-A1_3 Sc are calculated, and it is worth noting that 2 × 2 × 2 supercell models with a point defect are used for off-stoichiometric L1_2-A1_3 Sc in the calculation. Then employing calculated elastic constants, the values of Young＇s modulus, shear modulus, bulk modulus, anisotropic index, G/B ratio, Cauchy pressure, and Poisson ratio of stoichiometric and off-stoichiometricL1_2-A1_3 Sc are computed. And lastly, combining these data with point defect concentrations of off-stoichiometric L1_2-A1_3 Sc at 1000 K, the comprehensive effects of four point defects on elastic properties of L1_2-A1_3 Sc are evaluated. The four point defects coexist inL1_2-A1_3 Sc as we know from the calculations of equilibrium point defect density. The conclusions are as follows. 1） The point defects can cause of

关 键 词：L12-Al3Sc 点缺陷浓度 弹性模量 第一性原理 

分 类 号：O414.1[理学—理论物理]