Influences of Si and C addition on microstructure and mechanical properties of Fe2.5CoNiCu high-entropy alloy

To evaluate the role of non-metallic element (Si and C) on the microstructural evolution and mechanical properties of Fe2.5CoNiCu high-entropy alloys (HEAs), two series of Fe2.5CoNiCuSix (x=0.1-0.3, molar fraction) and Fe2.5CoNiCuCx (x=0.15-0.4, molar fraction) HEAs were prepared by vacuum induction melting. The results show that the amounts of C and Si additions significantly stimulate the transformation of BCC/FCC dual phases into a single FCC structure, and the microstructural evolution appears to be more strongly influenced by the C addition. The Fe2.5CoNiCuSi0.2 HEA presents high hardness (HV 439.5) and tensile strength (868 MPa), which is attributed to the solution strengthening and grain refinement effect. Both the hardness and strength of Fe2.5CoNiCuCx HEAs increase with the addition of C, due to the formation of carbides and solution strengthening. This demonstrates that adding non-metallic element (C or Si) is a viable approach for enhancing the strength and hardness of HEAs.