中文摘要：

采用金相显微镜、扫描电镜及能谱、透射电镜、扫描开尔文探针力显微镜对7A52铝合金的第二相进行观察及表征,并对微米量级的第二相进行电位测试。结果表明：长条状的η相与基体非共格,其强化效果较弱;圆片状的η＇相与基体半共格,是最主要的时效强化相;近似方块状的Al6Mn分布在晶界和晶内;近似于球形的Al3Zr粒子尺寸小、密度大,能够强烈地钉扎位错;形状不规则的AlMnFe和Mg2Si沿轧制方向弥散分布在基体上,其伏打电位均低于基体的电位,在腐蚀环境中容易被溶解而腐蚀,成为应力腐蚀裂纹源;而且同类相的尺寸不同,AlMnFe相对基体的伏打电位值也不同;Al6（Mn,Fe）相对基体的伏打电位值要比Mg2Si的更低,说明在腐蚀环境中,Al6（Mn,Fe）更容易被腐蚀。本试验有助于分析应力腐蚀断裂中裂纹的起始点。

英文摘要：

The metallographic microscope,scanning electron microscope,energy dispersive spectrometer,scanning Kelvin probe force microscope were used to observe and characterize the secondary phases of 7A52 aluminum alloy,and the volta potential of micron dimension secondary phases was tested.The results indicate that the - phase in long strip shape is incoherent with the matrix,whose strengthening effect is relatively weak.The η＇ phase in disk shape semi coherent with the matrix is the most important ageing strengthening phase.The Al6Mn precipitates in approximate square block shape distribute in the grains and grain boundaries.The Al3Zr precipitates in ball shape are very small and their density is very high,forming a strong pinning effect on the dislocations.The irregularly shaped intermetallics AlMnFe and Mg2Si disperse along the rolling direction in the matrix,and their volta potentials are lower than those of the matrix.Hereby,they are easy to be dissolved and corroded in erosive environments,thus becoming the stress corrosion cracking initiation sites.The same second phase with different sizes show different relative volta potentials to the matrix.The volta potential of AlMnFe is lower than that of Mg2Si intermetallics,which means that AlMnFe intermetallics are easier to be corroded in erosive environments.These measurement results will help in the crack initiation analysis in stress corrosion cracking.