Achieving strength-ductility synergy in HIP-CoCrFeNiMn high-entropy alloys via rolling and annealing

Abstract

Although the rolling-annealing process has been widely employed to tailor the microstructure and mechanical properties of high-entropy alloys, an optimal balance between strength and ductility has yet to be achieved. A deeper understanding of how different rolling modes and deformation levels affect recrystallization behavior and mechanical performance is essential for optimizing processing strategies. In this study, CrMnFeCoNi high-entropy alloys (HEAs) were fabricated by hot isostatic pressing, and the effects of the rolling annealing process on the microstructural evolution and mechanical properties of the alloys were systematically investigated. The results show that the prior particle boundaries (PPBs), composed of oxides, significantly influence the recrystallization behavior of the heavily cold-rolled CrMnFeCoNi HEAs. After annealing, the cold rolled large deformation specimen exhibited a highly inhomogeneous grain size distribution, with fine grains concentrated near the PPBs, accompanied by high kernel average misorientation values. Transmission electron microscopy revealed the presence of high-density dislocations and nanoscale secondary phases in these regions. In contrast, the hot-rolled specimens exhibited a higher fraction of twin boundaries, indicating more complete recrystallization. Mechanical testing demonstrated that the annealed CR75 % (75 % cold rolling reduction) specimen possessed the best combination of strength and ductility (Tensile strength: 782 MPa, Uniform elongation:34.9 %), which can be attributed to the synergistic effects of grain refinement, secondary phase strengthening, and dislocation strengthening. This study underscores the critical role of microstructural heterogeneity in tuning the properties of HEAs and provides a theoretical basis for their microstructural optimization.