Microstructural engineering through controlled thermomechanical processing to enhance the performance of the Cu-based multi-principal component alloy

Cu-based multi-principal component alloys (MPCAs) offer a promising route to combine the intrinsic functional advantages of copper with the microstructural complexity of multicomponent alloy systems. However, the interplay among thermomechanical processing, hierarchical microstructure, and the synergy between mechanical and corrosion properties remains insufficiently understood. In this work, a Cu 80 Co 5 Cr 5 Fe 5 Ni 5 MPCA was systematically investigated under tailored thermomechanical routes involving cold rolling and subsequent annealing, with emphasis on microstructural evolution, strengthening mechanisms, and corrosion behavior. The alloy exhibits a stable dual-phase face-centered-cubic microstructure consisting of a Cu-rich matrix and a CoCrFeNi-rich secondary phase with high-entropy-like compositional characteristics. Cold rolling induces severe grain fragmentation and high dislocation densities, leading to significant strength enhancement, whereas annealing promotes partial recrystallization and the formation of abundant annealing twins, thereby restoring ductility. Among all conditions, the CR80-9 MPCA achieves the optimal strength-ductility balance, which is attributed to the synergistic contributions of grain-boundary strengthening, hetero-deformation-induced strengthening arising from phase and domain heterogeneity, and supplementary precipitation strengthening from nano-precipitates. In addition to mechanical optimization, the refined and defect-engineered microstructure also improves corrosion resistance by facilitating the formation of a dense and chemically stable Cr 2 O 3 -rich passive film. These results demonstrate that thermomechanical processing provides an effective pathway for simultaneously regulating deformation mechanisms and corrosion behavior in Cu-based MPCAs. More broadly, this work presents a preliminary demonstration of a “functional matrix + high-entropy-like secondary phase” alloy-design strategy, in which the intrinsic functionality of a conventional base metal is retained while selected benefits of compositional complexity are introduced through a secondary phase.