Enhancing the strength-ductility synergy of dual-phase Al0.3CoCrFeNiTi0.3 high-entropy alloys through the regulation of B2 phase content

In this study, Al0.3CoCrFeNiTi0.3 high-entropy alloys (HEAs) with different phase contents and microstructures were prepared through cold rolling and recrystallization annealing. This method achieved a synergistic combination of strength and ductility, with the CR1000-1 HEA attaining an ultimate tensile strength of 1175 MPa and a uniform elongation of 21.5 %. In Al0.3CoCrFeNiTi0.3, there exist two distinct phase morphologies: dispersed structure and clustered structure. Using in-situ high-resolution digital image correlation at the microscale, it was observed that local strain in the dispersed structure tends to concentrate along the phase boundaries when a small strain is applied. As the applied strain increases, strain rapidly concentrates in the FCC phase and subsequently in the B2 phase. For the clustered structure, the strain initially concentrates rapidly within the B2 phase and then gradually diffuses into the FCC phase. The low degree of inhomogeneity of the dispersed structure reduces the likelihood of stress concentration and the risk of damage initiation. Furthermore, we observed the synergistic strain hardening effect produced by various deformation mechanisms, such as dislocation pile-ups, dislocation networks, interacting stacking faults, and deformation twins. This study provides valuable insights for the fabrication of dual-phase HEAs with enhanced strength-ductility synergy, applicable to a wide range of engineering applications.