(中南大学 材料科学与工程学院，长沙 410083)
摘 要: 借助超景深三维显微镜、扫描电镜、能谱分析、透射电镜、X射线物相分析、电化学测试等手段，对比不同Cu、Mg含量对2A12铝合金化铣粗糙度的影响。结果表明：当2A12铝合金中的Cu含量或Mg含量位于成分上限时，化铣后的表面粗糙度达到3.4 μm，合金合理的成分配比为4.02%Cu+1.39%Mg(质量分数)，化铣后的表面粗糙度为1.4 μm；θ和S的模拟相在化铣液中的电极电位较之Al基体更正，因而在电化学腐蚀过程中，θ相、S相充当阴极，其周围的Al基体会优先发生腐蚀；合金在化铣时，随着局部不均匀腐蚀的进行，形成相凸起、腐蚀坑等表面形貌特征；尺寸为50 μm左右的大型腐蚀坑是造成表面粗糙度增大的主要原因，晶内小尺寸的弥散T相(Al20Cu2Mn3)对化铣粗糙度的影响较小。
关键字: 2A12铝合金；Cu含量；Mg含量；化铣；表面粗糙度；微观组织；模拟相
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effect of different Cu and Mg content on the surface roughness of 2A12 Al alloy after chemical milling was investigated by ultra-depth three-dimensional microscope, scanning electron microscope with energy dispersive X-ray spectroscopy, transmission electron microscope, X-ray diffraction analysis and electrochemical measurement. The results indicate that, when the Cu or Mg content in the alloy is at the upper limit of the composition, the surface roughness after milling is 3.4 μm. The reasonable distribution ratio of the alloy is 4.02%Cu+1.39%Mg (mass fraction). The surface roughness after milling is 1.4 μm. The corrosion potentials of the simulated θ phase and S phase in chemical milling solution are more positive than that of the Al matrix. During the electrochemical corrosion process, the θ phase and S phase act as cathodic zone and lead the Al matrix around them be preferentially corroded. Besides, the development of local nonuniform-corrosion results in phase protrusion and corrosion pit. The large-scale corrosion pit with a size of about 50 μm is the main cause to increase surface roughness, whereas, the small-sized intragranular dispersoid such as T-phase (Al20Cu2Mn3) has little influence on it.
Key words: 2A12 aluninum alloy; Cu content; Mg content; chemical milling; surface roughness; microstructure; simulated phase
