Cu掺杂6000系铝合金中β?相的第一性原理研究

First-principles study of β" phase in Cu doped 6000-series aluminum alloys

采用基于密度泛函理论的投影缀加平面波方法和广义梯度近似,研究Cu掺杂对6000系铝合金中主要强化相β"相(Mg_5Al_2Si_4)的几何结构、相稳定性和电子结构的影响。结果表明:β"相的晶胞参数与文献报道相符。掺杂Cu后体系的晶胞形状发生微小变形且体积减小,而不同掺杂浓度和掺杂位置对掺Cu结构Mg_(5-x)Al_(2-y)Si_4Cu_(x+y)的几何性质影响不同,进而影响β"相和Al基体之间的晶格错配度;Cu既替代Mg1又替代Al原子和Cu只替代Al原子的结构在合金中更容易形成,而Cu只替代Mg1原子的结构在合金中不易形成,该计算结果与实验报道相符。电子结构分析表明,掺杂Cu后形成的Mg_(5-x)Al_(2-y)Si_4Cu_(x+y)相结构的稳定性和体系在费米能级附近的赝能隙密切相关。

β"(Mg5Al2Si4)phase is the main strengthening phase in 6000-series aluminum alloys.The effect of Cu-doping on the geometrical structure,the phase stability and the electronic properties ofβ"(Mg5Al2Si4)phase were investigated by using projector augmented wave method and the generalized gradient approximation based on density functional theory.The results show that the calculated equilibrium lattice parameters ofβ"phase are in good agreement with available experimental results.After Cu incorporates intoβ"phase,the cell shape changes slightly and the cell volume decreases.Various doping contents and doping sites result in various geometrical properties of Cu-doped structures,which then impacts the lattice mismatch betweenβ"and Al matrix.The structures in which Cu atoms replace both Mg1 and Al atoms,or only replace Al atoms are easier to form in the alloys,while it is harder to form in the alloys for the structures,in which Cu atoms only replace Mg1 atoms,which is supported by experimental results.The analysis of electronic structures shows that the phase stability of the Cu-doped structures Mg5-xAl2-ySi4Cux+y is closely related to the pseudo gap near the Fermi level.