Quantitative study of the solute clustering and precipitation in a pre-stretched Al-Cu-Mg-Ag alloy

The effect of 2.5% pre-stretching on the solute clustering and subsequent precipitation of an initial aged Al-Cu-Mg-Ag alloy is investigated by quantitative transmission electron microscopy (TEM) and atom probe tomography (APT) technique. In present work, 2.5% pre-stretching is found to restrict the dense precipitation of Ω phase, leading to the slower age-hardening response at 180 °C. The dominant Mg-Ag co-clustering, as revealed in non-stretched alloy, becomes weak by 2.5% pre-stretching prior to aging. This suppressed Mg-Ag co-clustering leads to a steep drop of the number density of Mg-Ag co-clusters by 70% and finally fails to induce the formation of high density Ω plates. High density dislocations introduced by pre-stretching also serve as the heterogeneous nucleation sites of θ′ phase and favor an enhanced precipitation of coarse θ′ needles. In addition, pre-stretching also exhibits a negative effect on initial Cu-Mg co-clustering. - Highlights: • 2.5% Pre-stretching greatly reduces the age-hardening level of Al-Cu-Mg-Ag alloy. • Pre-stretching significantly suppresses the initial Mg-Ag co-clustering. • Pre-stretching is detrimental to the dense precipitation of Ω phase. • The θ′ precipitation is considerably promoted by pre-stretching. • Pre-stretching also shows its negative effect on Cu-Mg co-clustering.