Effects of Crxmo(0.2-X) Addition on the Dispersoids Evolution and Mechanical Properties of Al-Cu-Mg-Ag-Mn Alloy

Unlike the rod-like T-Al20Cu2Mn3 dispersoids, the spherical Al7(Cr, Mn) and Al6(Fe, Mn, Mo) precipitated in Al-Cu-Mg-Ag-Mn alloys with CrxMo(0.2-x) addition, which can retain the deformed substructure and act as a dispersion reinforcement. In this study, the precipiation behavior of dispersoids in Al-Cu-Mg-Ag-Mn alloys with various CrxMo(0.2-x) (x=0.15, 0.10, 0.05wt.%) at 400℃/12h+515℃/24h homogenization was investigated. The compositional and structural evolution of dispersoids in Al-Cu-Mg-Ag-Mn alloys were studied by optical microscopy and atomic resolution high-angle annular dark-field scanning transmission electron microscopy. The effects of CrxMo(0.2-x) addition on morphology, size and number density of dispersoids inhibited the recrystallization behavior and improved the mechanical properties of alloys in varying degrees. When x=0.15 in CrxMo(0.2-x), the large amount of Al7(Cr, Mn) precipitates to refine the T-Al20Cu2Mn3 and dispersoid-free zones decreases(DFZ) obviouly. With x decreasing to 0.05, the homogeneous Al6(Fe, Mn, Mo) dispersoids presents the opposite precipitation trend of T-Al20Cu2Mn3 to compensate for the DFZ. During the deformation and subsequent heat treatment, the Cr0.05Mo0.15 alloy retains the highest substructure and dislocation density due to the highest number density of spherical dipersoids, thus exhibiting excellent mechanical properties at ambient and elevated temperature.