Enhanced damage tolerance through reconstructing residual stress and Cu-Mg co-clusters by pre-rolling in an Al-Cu-Mg alloy

The damage tolerance of Al-Cu-Mg alloy sheet was successfully improved by pre-rolling with small reduction (6.1%) rather than large reduction (12.2% and 21.7%). By this 6.1% pre-rolling, most of deformation only occurs at the surface layer of sheet, but not at the center layer. A protected compressive stress gradient was created, i.e., compressive stress gradually decreased from surface to center layer. Besides, atom probe tomography analysis showed that compared to center layer, large Cu-Mg co-clusters (50-100 atoms) with higher number density formed at surface layer. This led to greater module hardening and ordering hardening in surface layer than in center layer. Both the distributions of compressive stress and Cu-Mg co-clusters were responsible for the enhanced damage tolerance of alloy sheet.