Abstract:The tensile properties, aging precipitate type and distribution in Al-Cu-Li-(0.35Mg)-(0.2In) alloy were investigated. In the T6 aged Al-Cu-Li alloy, the aging precipitate are T1(Al2CuLi) and ?? (Al2Cu). As 0.2%In is added, many square-shaped cubic precipitates Al5Cu6Li2 are formed at early aging stage and their size keeps stable with aging time extension. Meanwhile, ? ? precipitation is advanced. The alloy?s aging response is therefore accelerated and its strength is enhanced. The combined addition of In+Mg suppresses the precipitation of cubic Al5Cu6Li2, but plays a role in promoting T1 precipitation instead. This role is smaller than that of combined addition of Ag+Mg in Al-Cu-Li alloy 2050, which results in a lower strength of the In+Mg micro-alloyed Al-Cu-Li alloy than that of the Ag+Mg micro-alloyed Al-Cu-Li alloy 2050. At T8 temper, the role of both In independent addition and In+Mg combined addition is suppressed by the dislocations introduced by plastic deformation prior to artificial aging.