The role of trace Nb in enhancing the strength-ductility combination of a Ni2CoCrFe-based high-entropy alloy via thermo-mechanical processing

In the present work, the role of trace Nb was investigated in enhancing the strength-ductility combination of the (Ni2CoCrFe)88.25(WMo)3Al5Ti3Nb0.75 high-entropy alloy. It was found that trace Nb can improve the heterogeneous microstructure, including the formation of the high-density (Ti, Nb)-rich phase instead of the (Ti, W, Mo)-rich phase, the refinement of σ and γ' phases, the production of the large amounts of stacking faults and Lomer-Cottrell locks. The strength-ductility combination of the alloy was enhanced via the improvement of the heterogeneous microstructure in thermo-mechanical processing. The results suggest that the addition of trace Nb is a promising method for enhancing the strength-ductility combination of this kind of alloys. •The (Ti, Nb)-rich phase formed instead of the (Ti, W, Mo)-rich phase.•The σ precipitated particles were refined with Nb addition.•A high density of ultra-fine γ'-LI2 precipitates formed with 4–10 nm in size.•The recrystallization was retarded due to the addition of trace Nb.•Trace Nb can improve the heterogeneous microstructure and tensile property.