(1. 重慶大學(xué) 材料科學(xué)與工程學(xué)院，重慶 400044；
2. 重慶大學(xué) 電子顯微中心，重慶 400044；
3. 重慶大學(xué) 物理學(xué)院，重慶 400044)
摘 要: 采用基于密度泛函理論的投影綴加平面波方法和廣義梯度近似，研究Cu摻雜對6000系鋁合金中主要強化相β？相(Mg5Al2Si4)的幾何結(jié)構(gòu)、相穩(wěn)定性和電子結(jié)構(gòu)的影響。結(jié)果表明：β？相的晶胞參數(shù)與文獻報道相符。摻雜Cu后體系的晶胞形狀發(fā)生微小變形且體積減小，而不同摻雜濃度和摻雜位置對摻Cu結(jié)構(gòu)Mg5-xAl2-ySi4Cux+y的幾何性質(zhì)影響不同，進而影響β？相和Al基體之間的晶格錯配度；Cu既替代Mg1又替代Al原子和Cu只替代Al原子的結(jié)構(gòu)在合金中更容易形成，而Cu只替代Mg1原子的結(jié)構(gòu)在合金中不易形成，該計算結(jié)果與實驗報道相符。電子結(jié)構(gòu)分析表明，摻雜Cu后形成的Mg5-xAl2-ySi4Cux+y相結(jié)構(gòu)的穩(wěn)定性和體系在費米能級附近的贗能隙密切相關(guān)。
關(guān)鍵字: 第一性原理；6000系鋁合金；強化相β？相；相結(jié)構(gòu)穩(wěn)定性；Cu摻雜
（1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
2. Electron Microscopy Center, Chongqing University, Chongqing 400044, China;
3. College of Physics, Chongqing University, Chongqing 400044, China）
Abstract: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 of β？(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 of β？ phase are in good agreement with available experimental results. After Cu incorporates into β？ 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 between β？ 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.
Key words: first-principles; 6000-series aluminum alloys; strengthening β？ phase; phase structure stability; Cu-doping
