Obtaining a strong and ductile Co-rich high entropy alloy via synergistic effect of pre-twinning and nanolamellar L12 precipitates

Alloys with high strength and competent ductility are highly demanded for modern engineering applications but difficult to design and prepare. In this study, we design a Co-rich Co₃₅Cr₂₀Fe₂₀Ni₂₀Al₂Ti₃ HEA that exhibits excellent tensile properties, facilitated by unique microstructures, namely pre-twins and nanolamellar L1₂ precipitates, which are introduced via multistep deformation and annealing. Comprehensive microstructural characterization, carried out through electron back scattering diffraction and transmission electron microscopy, demonstrates that interactions among lattice dislocations, pre-twins and nanolamellar L1₂ precipitates raise the dislocations slip stress barrier and dislocation storage rate, gifting the HEA a high strength and ductility mechanical properties. The present study provides insight into the fabrication of ultra-strong and ductile HEAs by tuning the substructures.