Influence of the Deformation Degree on the Evolution of the Microstructure and Properties of Al-10.0Zn-2.7Mg-2.3Cu Alloy During Short-Flow Thermo-Mechanical Treatment

A simple short-flow thermo-mechanical treatment (TMT) named L-ITMT (consisting of three steps: solution, warm deformation, and solution) was applied to ultra-high-strength Al-10.0Zn-2.7Mg-2.3Cu alloy to study the influence of the deformation degree on the particle distribution, resolubility, microstructure evolution, recrystallization mechanism, formation and development of deformation bonds, and mechanical properties. Increasing the rolling deformation during the L-ITMT process can effectively break up the second phase at the grain boundary and promote its dissolution, which is beneficial to aging precipitation strengthening and improves the strength of the alloy. The dominant mechanism changes from recovery to recrystallization when the deformation degree reaches 80%. As the strain increases, the deformation band becomes flatter and eventually becomes nearly parallel to the RD direction, promoting the occurrence of geometric recrystallization or continuous recrystallization (CRX). Under high-strain conditions, the formation mechanisms of recrystallized grains include discontinuous recrystallization (DRX), CRX, and particle-stimulated nucleation (PSN), but the main contributions to the formation of large-area fine-grained bands are CRX and PSN. The results showed that as the deformation degree increased from 10% to 80%, the improvement of solid solubility and grain refinement in the short-flow TMT process increased the ultimate tensile strength (701 MPa), yield strength (658 MPa), and elongation (11.3%) of the alloy by 15.7%, 10.8%, and 842%, respectively. This shows that the short L-ITMT process has a synergistic effect in significantly improving the plasticity and maintaining the strength of this ultra-high strength Al-Zn-Mg-Cu alloy.