Tailoring microstructures and tensile properties of a precipitation-strengthened (FeCoNi)94Ti6 medium-entropy alloy

The coherent precipitate L1(2)-type Ni3Ti nanoclusters and nano-sized particles in a fcc-FeCoNi medium-entropy alloy (MEA) matrix were designed and realized through minor Ti addition. The mechanical properties were modulated by thermo-mechanical processing and various annealing treatments, which leads to different hardening mechanisms such as dislocation strengthening and precipitation strengthening. An excellent combination of yield strength (similar to 893 MPa), ultimate tensile strength (UTS similar to 1263 MPa) and ductility (similar to 24% elongation) can be achieved because of the precipitation strengthening from the L1(2) type Ni3Ti nano-sized precipitates. The present study is important not only for understanding the strengthening mechanisms of metallic materials, but also provides a generic way to obtain the desirable mechanical properties of alloys via microstructural regulation. (C) 2020 Elsevier B.V. All rights reserved.