Phase modulation of bcc-structured Fe₃₅Mn₂₅Al₁₅Cr₁₀Ni₁₅ high-entropy alloy by interstitial carbon

High-entropy alloys (HEAs) usually contain more than five alloying elements. The ductility of a body-centered cubic (bcc)-type HEA typically is lower than that of their face-centered cubic (fcc) counterpart. And low ductility restricts engineering applications of the bcc-structured HEAs. In engineering materials, improvement in ductility usually results in deduction of mechanical strength. A method to improve both mechanical strength and ductility in a bcc-structured HEA was proposed by adding interstitial carbon. Experimental results showed that replacement of 5 at.% Cr with 5 at.% C in a bcc-structured Fe₃₅Mn₂₅Al₁₅Cr₁₀Ni₁₅ HEA resulted in an increase in fcc phase from 0.3 to 93.7 vol.%. Strength and ductility increased at the same time. The transition of bcc-structure to fcc-structure along with a remaining small amount of bcc phase improved mechanical properties. This work indicates that interstitial carbon can be employed to modulate the fraction of constituent phases in a bcc-structured HEA to enhance engineering mechanical properties.