Microstructure of a new Al-Cu-Mn high strength aluminum alloy was investigated by metallurgical microscope

transmission electron microscope（TEM）

scanning electron microscopy（SEM）

electron diffraction and energy spectrum（EDS）

XRD（X-ray diffraction）.The results reveal thatθ′precipitate phase is dominant in the alloy with someθdisperoids.The dispersedly fine T-Al12Mn2 Cu phase can be observed in the microstructure

playing a role in dispersed strengthening.In addition

Cd particle with approximately 2nm in size can be observed in the matrix phase to promote the nucleation and growth of strengthening phase.Microstructure of the alloy is composed of equaixed crystal with 30

8

0μm

meanwhile

texture is absent apparently.EDS analysis reveals that there exists composition segregation

and RE element is mainly segregated at the grain boundary.PFZ zone can be observed in the alloy

and fine needle N phase withμm level in size is precipitated from the grain boundary

which can decrease the elongation of the alloy.So the quantity of the brittle phase should be decreased as possible.