The effect of carbon on the microstructures and mechanical properties of non-equiatomic Cr15Cu5Fe20Mn25Ni35 high-entropy alloy

This study investigates the effects of carbon addition on the microstructure and mechanical properties of a single-phase face-centered cubic (FCC) Cr₁₅Cu₅Fe₂₀Mn₂₅Ni₃₅ high-entropy alloy (HEA) at room temperature. The alloy was identified as a promising single-phase FCC candidate through systematic thermodynamic calculations using the Calculation of Phase Diagrams (CALPHAD) method and Thermo-Calc software, with validation from X-ray diffraction analysis of the as-cast alloy. The introduction of carbon at concentrations of 0.5 and 1 atomic percent increased the yield strength from 250 MPa to 300 MPa and 350 MPa, respectively, and tensile strength from 500 MPa to 550 MPa and 600 MPa, while enhancing elongation to failure from 20 % to 25 % and 30 %. Microstructural characterization using X-ray diffraction, scanning electron microscopy, and electron backscatter diffraction revealed no alteration in the FCC structure, but a refinement of grain size from 10 μm to 5 μm and a more random crystallographic texture. Additionally, transmission electron microscopy (TEM) analysis demonstrated dense, parallel deformation twins in the alloy with 1 atomic percent of carbon, confirming that twinning significantly contributes to improved ductility and strain hardening. The strengthening effects of carbon are attributed to solid solution strengthening and mechanisms such as twinning. These findings provide valuable insights into tailoring HEA properties through interstitial modifications, contributing to the broader understanding of materials science and the development of high-performance alloys for various applications.