Optimization of strength and thermal stability in an Al–Cu–Mg alloy through tailored thermomechanical processing with intermediate ageing

This study explores the optimization of mechanical strength and microstructural stability in Al-Cu-Mg alloys through tailored thermomechanical processing. Various routes—comprising cold rolling, annealing, and intermediate aging at 130°C, 170°C, and 200°C—were evaluated to develop thermally stable microstructures capable of withstanding a final heat treatment at 300°C. Microstructural characterization revealed that while the types of intermetallic phases (AlCuMnFeSi and Al 7 Cu 2 (Fe,Mn)) remained consistent, their size distribution and softening kinetics were highly sensitive to the processing sequence. A key finding was that particle size distribution exerted a more profound influence on tensile behavior than the total phase volume fraction. Intermediate aging at 170°C proved pivotal, acting as a "fusion barrier" that suppressed excessive particle coarsening and regulated the driving force for softening. Samples processed via this route demonstrated superior tensile strengths of 610-630 MPa, elongation of 8.1%-9.4%, and controlled softening levels (64%-68%). These results indicate an optimal synergy between mechanical integrity and microstructural stability, highlighting the effectiveness of strategic intermediate aging in maintaining high-performance properties under elevated thermal exposure.