Ductilizing brittle high-entropy alloys via tailoring valence electron concentrations of precipitates by controlled elemental partitioning

Abstract

High-strength high-entropy alloys (HEAs) reinforced by hard intermetallics generally show a propensity for embrittlement, significantly undercutting their applications. Here we report a strategy to intrinsically toughen strong-yet-brittle HEAs via altering the valence electron concentration (VEC) of precipitates. It was found that a decrease of the VEC of precipitates by Co substitution for Ni atoms effectively destabilizes the brittle hexagonal-ordered precipitate and promotes the formation of ductile cubic-ordered nano-precipitates in Ni–Co–Fe–Cr–Ti system. Benefiting from such a transformation, a fivefold enhancement of tensile elongation (from 7% to 35%) was successfully achieved together with a simultaneously improved strength up to ∼1.35 GPa.

Keywords

• High-entropy alloys
• valence electron concentration
• phase transformation
• precipitation strengthening