摘要
采用基于密度泛函理论的第一性原理计算方法获得了Er在Al-Er合金中的的固溶度曲线。在计算溶解焓过程中采用了对Er的4f电子分别视为核心电子和价电子的冻结核近似和标准近似。2种近似下计算获得的hR20、cP4和hP8结构Al3Er对应的Er的溶解焓分别为–1.003和–0.767eV/Eratom,–0.987和–0.757eV/Eratom,–0.967和–0.713eV/Er atom。动力学计算获得的剩余熵分别为3.301,3.229和3.309 kB/Er atom。利用加权平均获得的溶解焓值和剩余熵结果模拟获得的cP4-Al3Er对应的固溶度曲线符合实验结果,说明4f电子在计算中所起的作用不可忽视。计算获得的hR20和cP4结构Al3Er对应的Er的固溶度量值近似相等,远小于hP8结构对应的固溶度值。结合结构分析显示,cP4结构比hR20结构简单是造成cP4结构Al3Er更易从固溶体中析出的主要原因,与实验观察结果相符。
The solubility curves of Er in Al-Er alloys were obtained by first principles calculations based on the density functional theory.The solution energies of Er atoms in these Al-Er alloys were calculated using the“frozen core”approximation and“standard potential”approximation for the 4f electrons.The calculated results show that the solution energies of hR20,cP4 and hP8-Al3Er are–1.003 and–0.767 eV/Er atom,–0.987 and–0.757 eV/Er atom,–0.967 and–0.713 eV/Er atom,respectively,obtained from the two approximations.The lattice dynamics calculation shows that the excess enthalpies of hR20,cP4 and hP8-Al3Er are 3.301,3.229 and 3.309 kB/Er atom.The simulated solubility curves were obtained by combining the lattice dynamics values and the weighted average of the solution energy values.The calculated solubility curves of cP4-Al3Er are consistent with the experimental values,which indicates that the 4f electrons play a very important role.In addition,the solubility curve of cP4-Al3Er is very close to that of the hR20-Al3Er,but lower than that of hP8-Al3Er at the same temperature.The chemical driving forces corresponding to the solubility curves of hR20 and cP4-Al3Er are also close to each other,but larger than that of the hP8-Al3Er.Due to the smaller interfacial energy in Al matrix of cP4-Al3Er than that of hR20-Al3Er,it could be deduced that the cP4-Al3Er precipitation is the first in priority order,which is consistent with the experimental observations.
作者
高春来
高坤元
熊湘沅
黄晖
文胜平
吴晓蓝
聂祚仁
Gao Chunlai;Gao Kunyuan;Xiong Xiangyuan;Huang Hui;Wen Shengping;Wu Xiaolan;Nie Zuoren(Key Laboratory of Advanced Functional Materials,Ministry of Education,Beijing University of Technology,Beijing 100124,China)
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2020年第8期2738-2745,共8页
Rare Metal Materials and Engineering
基金
国家科技部重点研发项目(2016YFB0300801)
国家自然科学基金(51621003,51671005)
北京市自然科学基金(2162006)。
关键词
第一性原理
AL3ER
固溶度
溶解焓
剩余熵
first-principles
Al-Er alloys
solubility
solution enthalpy
excess entropy
