Effect of Ce addition on microstructure of Al20Cu2Mn3 twin phase in an Al-Cu-Mn casting alloy

► Rare earth element Ce can retard the formation of the Al20Cu2Mn3 twin phase in an Al-Cu-Mn casting alloy. ► Patterns of the particles of the Al20Cu2Mn3 phase in Al-Cu-Mn free Ce alloy are more diverse. ► The symmetry of neighboring components of twins is characterized by glide reflection and reflection. ► The twins of Al20Cu2Mn3 phase can enhance the mechanical properties of the Al-Cu-Mn casting alloys.