【摘要】 基于密度泛函理论方法,本文开展了氦掺杂AlΣ3((111)/180°)晶界数值模拟拉伸试验.计算结果表明,He在晶界中最低杂质形成能为2.942eV,偏析到晶界的偏析能为0.085eV;在拉伸条件下,清洁Σ3晶界的理论拉伸强度为9.65GPa,拉伸断裂从晶界界面开始;而He掺杂后,晶界的理论拉伸强度下降到7.14GPa,在断裂发生前应力曲线中出现平台效应,拉伸断裂从包含He杂质的界面开始.通过对比键长和电荷密度分布,本文认为He的满壳层电子结构一方面导致了He与Al之间仅有弱的电荷相互作用,另一方面He满壳层电子结构的电荷屏蔽效应也导致了周围Al—Al键的弱化,这是系统拉伸强度下降的主要原因.更多还原

【Abstract】 According to the first principles methods,we theoretically study the mechanical properties of He doped AlΣ3 grain boundary(GB).Our results show that He has the lowest formation energy 2.942 eV in GB and low segregation energy 0.085 eV from bulk to GB.Under the extending tensile,the clean GB has a theoretical strength of 8.95 GPa,and the crack appears first from the GB.While,after the He doping,the tensile strength reduces to 7.14 GPa,and one flat effect is present in the curve of strain-stress.By analyzing the variation of the bond-length and the charge distribution,we believe that He-induced reduction of tensile strength is probably ascribed to the weaker interaction between He and Al atoms as well as the weakening Al-Al bonds,owing to the charge screening by full-shell electron structure of He.更多还原