Microstructure evolution and mechanical properties of AlxCoCrFeNi high-entropy alloys by laser melting deposition

AlxCoCrFeNi (x = 0, 0.2, 0.45, 0.7 and 1) high entropy alloys (HEAs) have been successfully synthesized by laser melting deposition (LMD). It is found that the microstructure of LMD-CoCrFeNi HEA with increasing the content of Al has been transformed from a single face-centered cubic (FCC) phase to mixture of FCC + BCC duplex phases, and then to body-centered cubic (BCC/B2) phases. The addition of Al (Al-0.2, Al-0.45 and Al-0.7) remarkably improved the yield strength sigma(0.2) (from 138 MPa to 185 MPa, 262 MPa and 771 MPa) and the tensile strength sigma(t) (from 634 MPa to 675 MPa, 863 MPa and 1171 MPa) of the samples, with the prize of plasticity decrease from 46% to 45%, 41% and 11% in tension. This work provides an approach of LMD-fabricated CoCrFeNi-based HEAs with different Al addition to accommodate the microstructure and mechanical properties, and insights into the correlation of mechanical properties with the solid solution strengthening or/and the precipitation of hardening phase.

Automated summary

AlxCoCrFeNi high entropy alloys were successfully synthesized by laser melting deposition, with the microstructure transforming from a single FCC phase to a mixture of FCC + BCC phases as the Al content increased. The addition of Al significantly improved the yield strength and tensile strength while reducing plasticity in tension.