Mechanical properties and corrosion resistance characterization of a novel Co36Fe36Cr18Ni10 high-entropy alloy for bioimplants compared to 316L alloy.

• Co 36 Fe 36 Cr 18 Ni 10 with a single-fcc structure large numbers of twins and SFs to effectively strengthen the alloy matrix. • The recrystallized Co 36 Fe 36 Cr 18 Ni 10 alloy achieved strength and ductility trade-off compared to 316L ss. • Twin boundaries can effectively inhibit pitting and corrosion crack formation and expansion. • The free state of elemental Co reacts with other elements can form a more stable substance in the passivation film. The high strength, ductility, and corrosion resistance of alloys are highly desirable functional materials for biomedical applications. Multi-component alloys with a single face-centered-cubic (fcc) phase structure can provide superior ductility, while microstructures such as twins and stacking faults (SF) can be incorporated into the matrix to improve the strength of the alloy without damaging plasticity. Here, we have developed a single-fcc phase alloy Co 36 Fe 36 Cr 18 Ni 10 with low stacking faults energy, which can effectively produce annealed twins by recrystallization annealing after cold rolling. The microstructure and mechanical properties of Co 36 Fe 36 Cr 18 Ni 10 compared to commercial 316L alloy was methodically investigated by EBSD, TEM, and tensile testing. The results reveal that the Co 36 Fe 36 Cr 18 Ni 10 alloy contains more twin boundaries and a high density of nano-twins and SFs in the microstructure, which effectively improve the strength of Co 36 Fe 36 Cr 18 Ni 10 alloy meanwhile maintaining a similar ductility to commercial 316L. The corrosion behavior of Co 36 Fe 36 Cr 18 Ni 10 and 316L in simulated body fluids has been investigated using electrochemical characterization, indicated that compared to 316L ss, pitting in Co 36 Fe 36 Cr 18 Ni 10 alloys is easily inhibited and rapid re-passivation, meanwhile the twin boundaries were effective in weakening the formation of corrosion pits and impeded the expansion of corrosion crack. Compare the surfaces of the two alloys after passivation, apart from the Cr 2 O 3 /Cr(OH) 3 contained in the passive film, the interactions between Co and other components in the passivation film produce more indissoluble substances with a lower enthalpy of formation that will enhance the passive film stability of Co 36 Fe 36 Cr 18 Ni 10 alloy. [ABSTRACT FROM AUTHOR]