Enhanced synergy of strength-ductility and low-cycle fatigue resistance of high-entropy alloy through harmonic structure design

Compared with homogeneous structured materials, heterogeneous structured materials exhibit unprecedented performances. In the present work, a series of harmonic structured CoCrFeMnNi high-entropy alloys (HEAs) with different shell fractions were prepared by mechanical milling (MM) and spark plasma sintering (SPS) process. The effects of shell fraction on mechanical properties and low-cycle fatigue (LCF) performances were investigated at room temperature. Results show that the harmonic structured HEAs with a shell fraction between 20% and 40% demonstrate a combination of superior strength-ductility synergy and good LCF resistance. Development and rearrangement of dislocations dominantly occur in the coarse-grained areas (cores) during LCF process, while the ultrafine-grained areas (shells) show good cyclic stability. The enhanced strain hardening leads to a good balance of high strength and high ductility in the harmonic structured HEAs. Moreover, the enhanced ductility also restrains LCF failure.

Automated summary

Heterogeneous structured materials show unprecedented performances compared to homogeneous structured materials. In this study, harmonic structured high-entropy alloys (HEAs) with different shell fractions were prepared, and the effects of shell fraction on mechanical properties and low-cycle fatigue (LCF) performances were investigated at room temperature. The results show that harmonic structured HEAs with a shell fraction between 20% and 40% exhibit a combination of superior strength-ductility synergy and good LCF resistance.