Mo doping fine-tune electronic structure of FCC Fe-based medium-entropy alloys to synergy strength-ductility and corrosion resistance

Developing high strength, high ductility and corrosion resistant high- and medium-entropy alloys (H/MEAs) is a current research hotspot, which is primarily sourced from Ni/Co-rich H/MEAs and expensive. In this study, cost-effective (Fe 62 Co 8 Ni 15 Cr 15 ) 100-x Mo x (x = 0, 2, and 3 at.%) Fe-based MEAs were designed. The experimental results show that Mo doping leads to a better strength-ductility balance and improves the corrosion resistance. The (Fe 62 Co 8 Ni 15 Cr 15 ) 97 Mo 3 MEA shows excellent mechanical properties (600 MPa yield strength and 26% uniform elongation at 298 K; 990 MPa and 42% at 77 K) and corrosion-resistance (pitting potential ∼ 0.83V in 3.5 wt% NaCl solution), outperforming 316L stainless steel and several corrosion-resistant Ni/Co-rich H/MEAs. The deformation mechanism at 298 K is mainly dislocation slip, besides FCC-to-BCC phase transformation occurs at 77 K. First-principles calculations show that Mo doping reduces the alloy’s binding energy and O adsorption energy while increasing the Cl - migration barrier. Moreover, when Cl - adsorbs near Mo atoms, Mo weakens Cl - adsorption on Fe/Cr sites and reduces electronic interaction with Cl - . The experimental results show that Cr 2 O 3 and Mo oxides in the passive film enhance the corrosion resistance of the (Fe 62 Co 8 Ni 15 Cr 15 ) 97 Mo 3 MEA. This paper offers a reference for designing high-performance Fe-based MEAs.