7475铝合金中η相沿E/Al相界的非均匀析出机理

Heterogeneous Precipitation Mechanism of η Phase at E/Al Interface in 7475 Aluminum Alloy

采用高分辨透射电镜(HRTEM)和高角环形暗场扫描透射电镜(HAADF-STEM)中的三维重构技术,研究了7475铝合金中η相沿E/Al相界的非均匀析出行为及其形核和生长机理。结果表明,η相在不同的E相颗粒(具有不同形态和不同体积)或同一个E相颗粒的界面析出时,其形核位置、形核率、生长速率和形态有很大差异。E相的界面能和弹性应变能是η相在E/Al相界形核、生长和粗化的决定性因素。η相长大属于扩散控制转变,主要通过相界高速扩散传输溶质原子。

The heterogeneous precipitation behavior and nucleation and growth mechanisms of η phase at E/Al interfaces in 7475aluminum alloy were studied using high resolution transmission electron microscopy(HRTEM) and 3D reconstruction technique in high angle annular dark field scanning transmission electron microscopy(HAADF-STEM). It is found that the nucleation location, nucleation rate, growth rate and morphology of η phase are greatly different when η phase are formed at E particles with different morphology and volume or the same E particle. The decisive factors that affect the nucleation, growth and coarsening of η phase are the interface energy and elastic strain energy of E phase. The growth of η phase belongs to the diffusion-controlled transformation. Solute atoms are transferred by the interphase interface diffusion at a high speed.