Introducing dislocations and nanoprecipitates is an effective strategy to strengthen alloys, but reliable bulk quantification of dislocation density and coherent nanoprecipitate content remains challenging. Here, FeCoNiAlTi high-entropy alloys with high-density dislocation network and coherent nanoprecipitates were fabricated by selective laser melting and subsequent aging. Neutron diffraction reveals that aging introduces ∼35 vol.% coherent L1 2 nanoprecipitates with an ultralow lattice mismatch (∼0.050%) to the FCC matrix. Small-angle neutron scattering determines an average radius of ∼10.2 nm for the L1 2 nanoprecipitates. Line-profile analysis shows the dislocation density decreases from (13.9 ± 0.3) × 10 14 m -2 in the as-built state to (6.1 ± 0.1) × 10 14 m -2 after aging. Correspondingly, the yield strength increases to 1300 ± 20 MPa, dominated by the synergistic strengthening of L1 2 nanoprecipitation (618 MPa) and dislocation hardening (310 MPa). This work establishes a quantitative correlation between dislocation structures, coherent nanoprecipitation and mechanical performance in additively manufactured HEAs.
Shi et al. (Wed,) studied this question.