Pre-Aging Effect on the Formation of Omega Phase and Mechanical Properties of the Al-Cu-Mg-Ag Alloy

In the present work, different aging treatments were performed to investigate the pre-aging effect on the formation of Omega phase and mechanical properties in Al-Cu-Mg-Ag alloy. The results showed that pre-strain could inhibit the formation of Omega phases, which was detrimental to the alloy strength. Due to the introduction of pre-aging treatment before pre-strain, the adverse effect of pre-strain on the precipitation of the Omega phase was reduced, and the alloy strength was increased by at least 15 MPa. Besides this, increasing the pre-aging temperature promoted the precipitation of Omega phases, inhibited the formation of theta' phases, and improved the alloy strength. This was because the higher pre-aging temperature promoted more pre-precipitated Omega phases in the pre-aging process, and most of the pre-precipitated Omega phases could be retained and grew in the subsequent aging process. As a result, the tensile strength of the alloy increased from 523 MPa to 540 MPa. In addition, pre-aging with a higher temperature consumed more solute atoms, leading to less residual solute atoms in the matrix. Thus, the adverse effects of pre-strain, which inhibit the formation of clusters by the segregation of solute atoms, were reduced.