Unveiling the precipitation behavior and mechanical properties of Co-free Ni47-xFe30Cr12Mn8AlxTi3 high-entropy alloys

Precipitate hardening is considered as an effective method to strengthen High- and medium-entropy alloys (HEAs and MEAs), especially the recently developed Co-free HEAs/MEAs. In this work, a systematic study on precipitation and mechanical behaviors of a Co-free HEAs with dilute amount of Al addition, Ni47-xFe30Cr12Mn8AlxTi3 (x = 2 at.%, 5 at.% and 7 at.%), is presented. Results shown that the Ni45Fe30Cr12Mn8Al2Ti3 has a face-centered cubic (FCC) + L1(2) + eta three-phased structure. With increasing Al content, the formation of eta phase is inhibited, accompanying with an enhanced formation of B2 phase, and FCC + L1(2) + B2 three-phased structure is thus observed in alloys with x = 5 and 7. The constrained lattice mismatch between FCC matrix and L1(2) precipitates is decreased with increasing Al content, leading to an enhanced precipitation behavior of L1(2) phase. As a result of microstructural evolution, the mechanical properties of the aged HEAs changed: the Ni42Fe30Cr12Mn8Al5Ti3 alloy exhibits a better combination of a yield strength of 661 MPa and tensile ductility of 29.7% as compared to the 2 at.% Al alloyed HEA; and addition of Al beyond 5 at.% results in an increase of strength with a large expense of ductility. We believe that the present work is helpful for developing high-performance Co-free HEAs/MEAs strengthened by nanoprecipitates via composition optimizing. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This study systematically investigates the precipitation and mechanical behaviors of a Co-free HEA with a dilute amount of Al addition. The results show that the addition of Al affects the formation of different phases and the mechanical properties of the alloy. The study provides valuable insights for developing high-performance Co-free HEAs/MEAs strengthened by nanoprecipitates through composition optimization.