(廣西大學 物理科學與工程技術學院，南寧530004)
摘 要: 應用EET理論和改進的TFD理論對Al-Mg-Si合金時效過程中析出的U1與U2相的原子成鍵和結合能進行計算。結果表明：兩相晶胞中最強鍵和次強鍵都是Al—Si鍵，其鍵絡比基體Al晶胞中的最強鍵絡都強得多；兩析出相晶胞中都以較強的Al—Si鍵構成主要鍵絡骨架結構，起到增強基體鍵絡強度、強化合金的作用。由于析出相U1比析出相U2具有更強的Al—Si鍵絡結構，且結合能較大，因此，相對U2相來說，U1相更穩(wěn)定。計算結果還表明：(001)Al//(110)U1相界面處電荷保持連續(xù)且連續(xù)性較好，界面應變能較低，界面較穩(wěn)定；界面(001)Al// (010)U2處的面電荷密度偏離連續(xù)條件，因此在此界面處，應力較大，界面原子鍵匹配較差，界面儲能(應變能)較高，容易成為新相形核、長大和裂紋萌生的地方。
關鍵字: Al-Mg-Si 合金；U1和U2相；原子成鍵；力學性能
（College of Physics Science and Engineering, Guangxi University, Nanning 530004, China）
Abstract:Atomic bondings of U1 and U2 phases in Al-Mg-Si alloy during aging were calculated by using the EET theory and the improved TFD theory. The results show that the strongest bonding and the second strong bonding in two phases are both Al—Si bonds, which are stronger than those in Al matrix. The firm network structures of Al—Si bonds are formed in U1 and U2 phases to enhance the bond network and strengthen alloy, while the bonding networks of Al—Si in U1 phase are not only stronger than those in U2 phase, but also with greater combining energy, therefore the structure of U1 is more stable. The calculation results also show that the electron density on the interface (001)Al//(110)U1 between U1 and matrix of Al is continuous with lower strain energy so that the interface (0001)Al//(110)U1 is more stable, while that on the interface (001)Al//(010)U2 is not continuous with a greater stored energy, poor atom-matching and higher stored energy, which will lead to precipitate a new phase or form a creak to break the alloy.
Key words: Al-Mg-Si alloy; U1 and U2 phases; atomic bonding; mechanical property
