Strong Strain Hardening in a Cost-Effective Fe₆₀Cr₁₅Ni₁₆Al₉ Medium-Entropy Alloy via Carbon Alloying

The influence of carbon addition on the microstructure and room temperature mechanical properties of a FCC + BCC dual-phase Fe₆₀Cr₁₅Ni₁₆Al₉ medium-entropy alloy (MEA) was investigated. The results show that the addition of carbon increases the volume fraction of FCC phase and the strain hardening capacity, resulting in a superior combination of an ultimate tensile strength (UTS) of 1340 MPa and an elongation of 28%. Specifically, the current MEA exhibits a higher ratio of UTS to raw material prices compared to the majority of Fe-based MEAs and medium-/high-entropy alloys. The experimental and molecular dynamics simulation results show that the stronger strain hardening induced by carbon is primarily attributable to the stronger transformation-induced plasticity effects and higher dislocation density.