(廣西大學(xué) 物理科學(xué)與工程技術(shù)學(xué)院，南寧530004)
摘 要: 應(yīng)用EET理論和改進(jìn)的TFD理論對(duì)Al-Mg-Si合金時(shí)效過(guò)程中析出的U1與U2相的原子成鍵和結(jié)合能進(jìn)行計(jì)算。結(jié)果表明：兩相晶胞中最強(qiáng)鍵和次強(qiáng)鍵都是Al—Si鍵，其鍵絡(luò)比基體Al晶胞中的最強(qiáng)鍵絡(luò)都強(qiáng)得多；兩析出相晶胞中都以較強(qiáng)的Al—Si鍵構(gòu)成主要鍵絡(luò)骨架結(jié)構(gòu)，起到增強(qiáng)基體鍵絡(luò)強(qiáng)度、強(qiáng)化合金的作用。由于析出相U1比析出相U2具有更強(qiáng)的Al—Si鍵絡(luò)結(jié)構(gòu)，且結(jié)合能較大，因此，相對(duì)U2相來(lái)說(shuō)，U1相更穩(wěn)定。計(jì)算結(jié)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(yīng)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(yīng)力較大，界面原子鍵匹配較差，界面儲(chǔ)能(應(yīng)變能)較高，容易成為新相形核、長(zhǎng)大和裂紋萌生的地方。
關(guān)鍵字: Al-Mg-Si 合金；U1和U2相；原子成鍵；力學(xué)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
