摘要
利用扫描透射电镜技术结合第一原理计算,研究了新型高强Al-4.0Cu-1.0Li(wt.%)合金在165℃单级时效过程中T1相(Al2CuLi)的演变规律。实验结果表明:随着时效时间的延长,T1相存在两种生长方式,一种是沿着它的c轴方向正常生长,另一种是通过T1相的变体成核生长。T1相的变体由两个T1相单胞组成,并在两个单胞中间存在一层Li原子。通常,T1相的变体存在于Li原子过剩区,这种变体既可以单独形核,也可在T1相上形核。第一原理计算结果表明:对于T1相的结构,Van Smaalen模型能量最稳定,T1相的两种生长方式都具有能量合理性。
The evolution of T1 phase in the novel ultra-high strength Al-4.0Cu-1.0Li（wt.%） alloys aged at 165 ℃ was studied by means of high-angle annular dark field（HAADF） scanning transmission electron microscopy（STEM） and the first-principles calculations based on density functional theory（DFT）.The results show that the T1 phase particles may grow in two ways.One is that it grows thicker regularly along its c-axis.The other way is that it grows irregularly,forming a variant of the regular T1 phase precipitates,i.e.,a Li atomic layer exists between two T1 unit cells.This variant may form individually or together with the T1 particles in Li-excess area.The energy calculations indicate that the model proposed by Van Smaalen et al.for T1 phase is the most energetically favorable,and independent of the composition in Cu-rich layers.The atomic structure of the T1 variant and its formation enthalpy show that the existence of the variant is also energetically reasonable.
出处
《电子显微学报》
CAS
CSCD
2012年第4期308-314,共7页
Journal of Chinese Electron Microscopy Society
基金
国家重点基础研究发展计划资助项目(2009CB623704)
国家自然科学基金资助项目(No.50771043)
湖南省高校科技创新团队项目
