The Printability, Microstructure, and Mechanical Properties of Fe_80-MnCo₁₀Cr₁₀ High-Entropy Alloys Fabricated by...

This work investigated the effect of Fe/Mn ratio on the microstructure and mechanical properties of non-equimolar Fe_80-MnCo₁₀Cr₁₀ (x = 30% and 50%) high-entropy alloys (HEAs) fabricated by laser powder bed fusion (LPBF) additive manufacturing. Process optimization was conducted to achieve fully dense Fe₃₀Mn₅₀Co₁₀Cr₁₀ and Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEAs using a volumetric energy density of 105.82 J·mm^-3. The LPBF-printed Fe₃₀Mn₅₀Co₁₀Cr₁₀ HEA exhibited a single face-centered cubic (FCC) phase, while the Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEA featured a hexagonal close-packed (HCP) phase within the FCC matrix. Notably, the fraction of HCP phase in the Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEAs increased from 0.94 to 28.10%, with the deformation strain ranging from 0 to 20%. The single-phase Fe₃₀Mn₅₀Co₁₀Cr₁₀ HEA demonstrated a remarkable combination of high yield strength (580.65 MPa) and elongation (32.5%), which surpassed those achieved in the FeMnCoCr HEA system. Comparatively, the dual-phase Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEA exhibited inferior yield strength (487.60 MPa) and elongation (22.3%). However, it displayed superior ultimate tensile strength (744.90 MPa) compared to that in the Fe₃₀Mn₅₀Co₁₀Cr₁₀ HEA (687.70 MPa). The presence of FCC/HCP interfaces obtained in the Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEA resulted in stress concentration and crack expansion, thereby leading to reduced ductility but enhanced resistance against grain slip deformation. Consequently, these interfaces facilitated an earlier attainment of yield limit point and contributed to increased ultimate tensile strength in the Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEA. These findings provide valuable insights into the microstructure evolution and mechanical behavior of LPBF-printed metastable FeMnCoCr HEAs.