Tailoring microstructure and excellent tensile properties of Al-Cu-Mg-Mn alloy via extensive cold rolling

The effect of extensive cold rolling on the improved tensile properties of AA2624 (Al-3.9% Cu-1.2% Mg-0.39% Mn-0.16% Zn-0.14% Ti-0.10% Zr) via a significant microstructural evolution was investigated. The microstructure of Al-Cu-Mg-Mn (AA2624) before deformation consisted of large elongated grains with a mean size of 53 ± 2 μm and subgrains with a mean size of 32 ± 2 μm, which demonstrates a yield tensile strength of 139 ± 4 MPa and ultimate tensile strength of 373 ± 1 MPa with a total elongation of 23 ± 0.5%. The remarkable increase in both yield tensile strength, up to 596 ± 6 MPa, and ultimate tensile strength, up to 621 ± 0.4 MPa, of AA2624 alloy was obtained via extensive cold rolling to a strain of 1.62, wherein a total elongation reduces to 2%. The better tensile strength comes from two main ways: (a) grain/subgrain boundary strengthening related to the size of the crystallites bounded by deformation-induced high-angle boundaries and low-angle boundaries and (b) strain hardening related to highly increased dislocation density. Dislocation strengthening makes the main contribution of about 60% to the strength, especially at a reduction of ≤ 40%. At reductions of 60–80%, the dislocations and the deformation-induced LABs and HABs provide similar contributions to the strengthening; their combined effect accounts for approximately 80% of the increase in yield strength.