Breaking the strength-ductility trade-off via heterogeneous structure in FeCoCrNiMo0.2 high-entropy alloy
Fei Chen, Fei Liu, Yuanbiao Tan, Wei Shi, Song Xiang
Abstract
The synergistic effect between heterogeneous structures has been proved to enhance the strength and plasticity of alloys, especially in the context of single-phase face-centered cubic (FCC) high-entropy alloys with low stacking fault energy. This study explores the synergistic effects of heterogeneous structures on the strength and plasticity of single-phase FCC FeCoCrNiMo0.2 high-entropy alloys. Through a combination of cryogenic rolling and annealing at 1000 °C for 0.5 h (RA-1000), the alloy demonstrates exceptional strength-ductility synergy and work-hardening ability. The heterogeneous structure comprises fine grains, nano-scale rich- (Cr, Mo) σ phase, and high-density annealing twins. The interaction of σ precipitation and FCC matrix induces heterogeneous deformation-induced strengthening (HDI), while annealing twins and stacking faults act as barriers to dislocation movement, enhancing strength and ductility through a dynamic Hall-Petch effect. Additionally, chemically ordered structures, ordered L12 phase, and type 63 topologically close-packed phases in RA-1000 alloys contribute to improved strain hardening via anti-phase boundaries. This work provides valuable insights for designing multi-scale heterogeneous structures to strengthen high-entropy alloys.