(广西大学 物理科学与工程技术学院，南宁530004)
摘 要: 应用EET理论和改进的TFD理论对Al-Mg-Si合金时效过程中析出的U1与U2相的原子成键和结合能进行计算。结果表明：两相晶胞中最强键和次强键都是Al—Si键，其键络比基体Al晶胞中的最强键络都强得多；两析出相晶胞中都以较强的Al—Si键构成主要键络骨架结构，起到增强基体键络强度、强化合金的作用。由于析出相U1比析出相U2具有更强的Al—Si键络结构，且结合能较大，因此，相对U2相来说，U1相更稳定。计算结果还表明：(001)Al//(110)U1相界面处电荷保持连续且连续性较好，界面应变能较低，界面较稳定；界面(001)Al// (010)U2处的面电荷密度偏离连续条件，因此在此界面处，应力较大，界面原子键匹配较差，界面储能(应变能)较高，容易成为新相形核、长大和裂纹萌生的地方。
关键字: Al-Mg-Si 合金；U1和U2相；原子成键；力学性能
（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
