The structure determination of Al20Cu2Mn3 by near atomic resolution chemical mapping

Al20Cu2Mn3 phase is one kind of common dispersoids in aluminum alloys; however, the atomic arrangement of Al20Cu2Mn3 has not yet been clearly identified. Combining the atomic resolution high angle annular dark field and chemical composition quantitative results, three structure models of Al20Cu2Mn3 were derived basing on the isostructural Mn11Ni4Al60. The formation enthalpies and total energy were calculated using the first-principles approach. The structure of the Al20Cu2Mn3 phase with the minimal energy was identified, giving a fully relaxed structure with lattice parameters of a = 23.98 Å, b = 12.54 Å, c = 7.66 Å, which belongs to a space group of Bbmm. The determined structure is in excellent agreement with the near atomic resolution chemical mapping results.