Enhanced strength and corrosion resistance of a binder-jetted Ni35Co27.5Cr27.5Al5Ti5 high-entropy alloy through tailored coherent L12 nanoprecipitates

Challenges remain in producing high-performance alloys that contain multiple principal elements by binder jet 3D printing because of the grain coarsening induced by sintering, an issue that restricts the strengthening provided by grain refinement. In this study, a novel Ni35Co27.5Cr27.5Al5Ti5 high-entropy alloy was prepared through BJ3DP together with a subsequent heat treatment, with the aim of enhancing mechanical and corrosion properties by regulating the L12 precipitates. The sample in its as-sintered state is composed of a face-centered cubic matrix that incorporates submicron-sized L12 precipitates with sizes around 184 nm. Conversely, the aged sample displays a high density of coherent L12 nanoprecipitates approximately 7 nm in size, which raises the yield strength from 634 MPa to 723 MPa and the total elongation from 13.8% to 16.4% as a result of dislocation shearing involving the L12 nanoprecipitates. Electrochemical tests carried out in 3.5 wt.% NaCl solution indicate superior corrosion resistance for the alloy under all conditions when compared with 316L stainless steel. This enhancement stems from a distinctive self-healing passive film featuring a stable inner layer rich in Cr as well as a sacrificial outer layer enriched with Al and Ti. The obtained results illustrate the considerable potential of BJ3DP in the production of high-performance MPEAs.